Download 1.1 Autism Spectrum Disorder

COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
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Karen Hopmann
Th. Widdings Veg 50
N - 9020 Tromsø
[email protected]
Cognitive and Emotional Processing of Social Stimuli in
Students with Autistic Traits
An EMG Study
Words: 9164
01.06.2012
Master Thesis Neuropsychology
Experimental Research
Maastricht University (UM)
Faculty of Psychology & Neuroscience
Internship at: Universitetet i Tromsø (UiT) – Institute of Psychology
Supervisors: Ole Åsli (UiT), Hans Stauder/Petra Vlamings (UM)
COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
Content
Abstract ................................................................................................................................................... 3
Acknowledgements ................................................................................................................................. 4
1 Processing of Social Stimuli in Autism Spectrum Disorder................................................................. 5
1.1 Autism Spectrum Disorder ............................................................................................................ 5
1.1.1 Autistic phenotype. ................................................................................................................. 8
1.1.2 Facial processing in ASD. .................................................................................................... 11
1.2 Startle Eyeblink Response ........................................................................................................... 12
1.3 Hypotheses .................................................................................................................................. 14
1.4 Relevance .................................................................................................................................... 15
2 Method ............................................................................................................................................... 16
2.1 Participants .................................................................................................................................. 16
2.2 Materials ...................................................................................................................................... 16
2.2.1 EMG/picture presentation. ................................................................................................... 16
2.2.2 SAM/VAS subjective measure. .............................................................................................. 17
2.2.3 Autism spectrum quotient questionnaire. ............................................................................. 18
2.3 Procedure ..................................................................................................................................... 18
2.4 Apparatus and EMG .................................................................................................................... 19
2.5 Data Analysis .............................................................................................................................. 19
3 Results ................................................................................................................................................ 20
3.1 Autism Spectrum Quotient Questionnaire................................................................................... 20
3.2 Ratings ......................................................................................................................................... 20
3.3 Startle Eyeblink Response ........................................................................................................... 21
4 Discussion .......................................................................................................................................... 22
4.1 Hypotheses revisited.................................................................................................................... 23
4.2 Limitations .................................................................................................................................. 25
5 Conclusion .......................................................................................................................................... 27
References ............................................................................................................................................. 28
COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
Abstract
Autism spectrum disorder (ASD) is a pervasive developmental disorder that becomes
apparent early in an individual’s lifetime. As the name of the disorder indicates, autistic
symptoms occur on a spectrum. Less severe expressions of the symptoms can arise in a
normal student population, showing autistic traits. The current study investigated cognitive
and emotional processing of facial stimuli in a group of students scoring high (n = 12) versus
low (n = 16) on a test of autistic traits, the Autism Spectrum Quotient Questionnaire (AQ). To
test this, the startle eyeblink response, elicited by a white noise while watching pictures of
faces, was recorded with electromyography (EMG). No differences in startle eyeblink
response to facial stimuli between individuals scoring high and low on the AQ were found.
Moreover, a subjective test of arousal and valence revealed no differences between the
groups. For the EMG measure, the different emotions led to differences in startle eyeblink
responses. Here, fearful faces presented frontally elicited higher startle response magnitude
than frontally displayed angry faces and neutral faces presented from a 45° angle. In addition,
the angle of picture presentation exposed a significant difference, with frontally presented
pictures eliciting higher startle eyeblink responses than presentation from the side. It is
concluded that fear reactions in individuals with high autistic traits are comparable to those of
the control group.
Keywords: Autism spectrum disorder (ASD), social stimuli, fear, autistic traits, startle
eyeblink response
COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
Acknowledgements
I would like to thank my supervisor at Tromsø University, Ole Åsli, whose encouragement,
guidance and support from the initial to the final level enabled me to develop an
understanding of the subject. He has shown his support in a number of ways, starting with
laboratory instructions, guidance with writing, and last but not least given great support with
statistical analyses. Furthermore, giving me free rein to execute all laboratory work helped a
lot to develop independence in my work.
Also, I want to thank my supervisor at Maastricht University, Petra Vlamings, for her support
regarding background knowledge of ASD. I appreciate the help and support, especially when
the current topic had to be changed, and her knowledge of the current field of study.
My thanks go to Hans Stauder at Maastricht University for taking over for Petra Vlamings
without hesitation, when she was not able to supervise my work anymore. Without his effort,
a smooth delivery of my thesis would not have been possible.
Finally, I offer my regards to all of those who supported me in any respect during the
completion of the project, most especially to my family and friends.
Karen Hopmann
COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
1 Processing of Social Stimuli in Autism Spectrum Disorder
Flo and Kay Lyman, born in New Jersey in 1956, are the only known female savant
autistic twins in the world. Diagnosed with autism spectrum disorder, they have experienced
a lot of harassment throughout their lives. However, these twins seem to be unique in a lot of
ways. Flo and Kay can remember every day in detail since adolescence. They know what they
had for dinner or what the weather was like of any given day in the past. Asked which day of
the week it was on November 30th of 1938, they answer correctly that it was a Wednesday,
although they were not even born at that time. Their mental abilities and memories appear to
be special; however, the disorder of autism restricts them in their social acts. Flo and Kay
need routines, they live for themselves following the same patterns each and every day. They
seem to be absurdly obsessed with TV-star Dick Clark. The twins know about their
difficulties, but manage their lives in their own ways and appear happy and resilient.
(Retrieved April, 11, 2011, from
http://splicetv.com/work/clients/flo_and_kay_twin_savants.html;
http://www.examiner.com/article/flo-and-kay-twin-autistic-savants)
This case of two very special autistic women is a good example of the unique nature of
the disorder of autism. Savants are rare, yet most commonly observed in developmental
disorders like autism. These individuals have abilities which seem genius to a normal healthy
person, such as recalling accurate dates and events. Nevertheless, something that appears to
be a unique gift for someone can equally have severe consequences for the person concerned.
Autism spectrum disorder (ASD) is a heterogeneous syndrome restricting an individual’s life
in many aspects.
1.1 Autism Spectrum Disorder
In 1943, Leo Kanner made the first diagnosis of ‘infantile autism’ (Volkmar, State, &
Klin, 2009). Symptoms such as social impairments, repetitive behaviors, and difficulties with
language were described as the core symptoms (McIntosh, Reichmann-Decker, Winkielman,
& Wilbarger, 2006). However, the most noticeable sign was the “pervasive lack of interest in
other people, including their parents” (Klin & Volkmar, 1999, p. 248). Since then, diagnostic
tools, classifications, and different expressions of the disorder have been further developed
and explored. Nowadays, the syndrome is known under the overall term autism spectrum
disorder (ASD). The spectrum comprises many forms of symptom manifestations, varying
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from severe limitations in daily functioning to less severe forms of the disorder.
Approximately 1 in 100 children and adolescents are affected by the disorder today, many
more than originally assumed (Charman et al., 2011). Boys tend to be four to five times more
frequently affected than girls, while female patients generally suffer from more severe forms
of ASD (Klin & Volkmar, 1999).
While the basic symptoms described by Kanner around 70 years ago are generally still
applicable, such as the lack of social interactions, problems with communication, the
expression of repetitive behaviors, as well as the differentiation from schizophrenia, some are
now proven to be wrong. For instance, it has been established recently that parenting has
rather small to no influence on the development of autism, which is in contrast with Kanner’s
original suggestion that parents influence the syndrome pathogenesis (Klin & Volkmar,
1999). Moreover, Kanner falsely claimed that children suffering from infantile autism are
principally clever rather than mentally retarded. Today it is known that about half until up to
three-quarters of the autistic population have an IQ below 70. This demonstrates a connection
to syndromes like mental retardation (Barlow & Durand, 2002; Charman et al., 2011).
Furthermore, Charman et al. (2011) imply that especially verbal IQ is much lower in autistic
individuals in comparison to rather preserved performance IQ. This stands in contrast to what
was previously assumed. Therefore, the connection between use of verbal assessment forms
of IQ and communication problems in autistic individuals should be accounted for and needs
further investigation.
The spectrum comprises a large scale of symptom expressions. Five subtypes of ASD
are described by the DSM-IV-TR, shown in figure 1. These include Asperger’s syndrome,
autistic disorder, Rett’s disorder, childhood disintegrative disorder, and unspecified subtypes
(pervasive developmental disorder not otherwise specified, PDD-NOS). PDD-NOS
encompasses the largest amount of affected individuals (Barlow & Durand, 2002; Golaria,
Grill-Spector, & Reiss, 2006; Volkmar et al., 2009). Comorbidity is very common in
individuals with ASD and more than half of the affected patients additionally suffer from an
intellectual disability or experience other psychiatric problems (Charman et al., 2011).
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Autism spectrum disorder
Autistic
Disorder
Rett's Disorder
Childhood
Disintegrative
Disorder
Pervasive
Developmental
Disorder, Not
Otherwise Specified
Asperger's
Syndrome
Figure 1: The five subtypes of ASD as defined by the DSM-IV-TR (APA, 2000).
Along these lines, often mistakenly called autism, ASD is a pervasive developmental
disorder, characterized by expression of stereotyped behaviors, and impairments in non-verbal
communication skills and social interactions (American Psychiatric Association, 2000).
However, symptoms are extremely heterogeneous throughout the group of patients.
Difficulties, for example in executive functions, are recognized to be apparent, yet not
globally evident (South, Larson, Krauskopf, & Clawson, 2010). South et al. (2010) explain
this by the fact that inconsistent findings are common in a young field of research such as
autistic examinations. This heterogeneity has lead to further uncertainties in the description of
the causes of ASD.
There is convincing evidence to believe in a genetic predisposition of autism spectrum
disorder. In case of having one child suffering from ASD, the chance that siblings are affected
lies at about three to five percent, although they are often suffering from milder forms of the
disorder (Barlow & Durand, 2002; Rutter, 2006). This supports the theory that certain genes
are responsible for the development of ASD (Rutter, 2006; Volkmar et al., 2009). Yet, the
exact genes involved in the development of the disorder still need to be investigated. ASD
certainly is a disorder with many facets, and environmental factors are additionally
influencing the development. However, empirical support in the area of pathogenesis is very
rare, and symptom expression varies from individual to individual. The former suggestions of
parental influence, such as nurturing style, socioeconomic status, and causation through
vaccination, could furthermore not be confirmed in later studies (Barlow & Durand, 2002;
Klin & Volkmar, 1999; Rutter, 2006).
While the causes are relatively unknown, a reliable diagnosis can nowadays be made
already at an early age. Such early diagnoses were much less common a generation ago, when
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COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
ASD was mostly not recognized before children attended school (Rutter, 2006). Diagnoses
are mostly done by a pediatrician using specialized diagnostic tools. These include specific
scales which are appropriate for the assessment of ASD, such as the Autism Diagnostic
Observation Schedule (Volkmar et al., 2009). Four major components are important for a
successful diagnosis of ASD. These components comprise an early onset, dysfunctions in
social interactions and symbolic play, communicative problems, and stereotyped behaviors
with resistance to change (Klin & Volkmar, 1999). These are consistent with the typical
symptoms described in the DSM-IV-TR. With doctors and psychologists being more familiar
with the disorder and diagnostic tools getting more advanced, an early diagnosis can be made
more easily (Rutter, 2006).
The treatment, as much as the knowledge about the origin of the disorder, is still in its
fledgling stage. Different therapies exist, including behavioral and social therapy, as well as
pharmacological interventions. As up to three-quarters of the autistic population have an IQ
below 70, there are vast parallels between pervasive developmental disorders and individuals
who are mentally retarded (Barlow & Durand, 2002). Consequently, the treatment has some
overlap. As in mentally retarded individuals, no treatment until now can promise to restore
complete health, and can only improve the situation for the affected patients. Behavioral
therapies commonly aim at improving the integration into social life and reducing stereotyped
and repetitive behaviors, likewise improving communicative skills (Klin & Volkmar, 1999). It
is important to give social treatment frequently and start early with interventions to achieve
the best possible outcome (Barlow & Duran, 2002). While psychosocial and behavioral
treatment seems to improve some of the symptoms, the effectiveness of medication could not
be successfully proven. In particular, the heterogeneity of the disorder causes problems,
because no single drug can cure all of the symptoms of ASD in any given individual. Special
dietaries, vitamins, and some forms of medical treatment were used in the past, but did not
show significant effects. Pharmacological treatment might only help to reduce some
symptoms, and merely on a temporary basis (Barlow & Durand, 2002).
1.1.1 Autistic phenotype.
The name autism spectrum disorder alone implies a heterogeneous nature of the
disorder, with many aspects of symptom expression. Asperger’s syndrome, for example, is
often specified as a case of less severe autism, even though this generalization does not meet
the whole truth. However, patients suffering from Asperger’s syndrome generally have a
higher average IQ with preserved higher communication skills and fewer problems restricting
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normal living (Volkmar et al., 2009). They do, in spite of this, have problems with social
interactions and often need to follow routines, sometimes expressing abnormal patterns of
behavior. As language abilities are generally preserved, a less severe perception of the autistic
symptoms is common (Barlow & Durand, 2002). One example is that professors or other
intellectual people diagnosed with ASD are mostly suffering from a form of Asperger’s
syndrome. This indicates that also in a student population, autistic traits or cases are present.
Moreover, Barlow and Durand (2002) state that Asperger’s syndrome is often not diagnosed,
hence not recognized, indicating the presence of autistic symptoms in the normal population.
Furthermore, it is claimed that the spectrum of ASD can reach into the non-clinical
population, thus suggesting autistic traits in the neurotypical population (Suda et al., 2011).
Especially individuals with a family history of ASD or siblings diagnosed with some sort of
autistic disorder, have a greater chance to experience symptoms. Nevertheless, these
symptoms are generally less severe in siblings (Rutter, 2006). Due to this, there is a great
chance of finding an autistic phenotype in everyday life, such as in a student population on
university campuses. Particularly, students at faculties of natural sciences, such as
mathematics, physics and others, have been found to have a higher possibility of scoring in
the upper range when tested for autistic traits. One of those questionnaires testing for autistic
traits is the Autism Spectrum Quotient Questionnaire (AQ; Baron-Cohen, Wheelwright,
Skinner, Martin, & Clubley, 2001). With the AQ, a range of domains - such as social
problems - common for ASD can be assessed. Individuals scoring high on the AQ are seen to
have higher autistic traits. Ridley, Homewood, and Walters (2011) examined the performance
on motor and verbal tasks and found a correlation between motoric problems and higher
scores on the AQ, indicating a cerebellar dysfunction in people with autistic traits. They
claimed that these findings point toward an autistic spectrum or continuum reaching into the
non-clinical population, including the students tested in their study. An autistic phenotype
exists both in the clinical and non-clinical population.
In accordance with the assumption of South, Ozonoff and McMahon (2005) that
patients with Asperger’s syndrome and high-functioning autistic individuals can develop
special interests in the field of natural sciences, it is of high interest for the present study to
find participants interested in natural sciences. Especially students of mathematics, physics
and similar subjects will possibly contribute to a higher representation of the autistic
phenotype in a non-clinical population. The higher prevalence of autistic traits in these fields
of studies can be explained by the fact that autistic traits are often manifested in a greater
interest or focus on details instead of social interactions or information processing as a whole.
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There appears to be an overall interest in the natural, instead of the personal, environment
(Ridley et al., 2011).
Another explanation can be given by the ‘extreme male brain’ (EMB) theory of autism
by Baron-Cohen (2002), stating that an autistic brain might be “an extreme of the normal
male profile” (Suda et al., 2001, p. 7). Generally, there is a higher prevalence of autistic traits
in the neurotypical male population in contrast to females, supporting the EMB theory. The
study by Suda et al. (2011) showed that in face-to-face conversation a female brain shows
additional activation in the superior temporal sulcus, where empathy is recognized; whereas
male brains tend to show activation in the prefrontal cortex only - thus in the planning or
systemizing part. Given these outcomes, it can be theorized that male brains are often more
systematically driven than female brains. Precisely that is also stated by the empathizingsystemizing (E-S) theory (Baron-Cohen, 2005). The E-S theory states that the female brain is
“predominantly hard-wired for empathy and that the male brain is predominantly hard-wired
for understanding and building systems” (Baron-Cohen, 2005, p. 23). According to this
theory, there are three types of brains. The first one is the female or empathizing brain (type
E), the second one a male or systemizing brain (type S), and a third type, called the balanced
brain (type B), which comprises characteristics of both types. These categorizations and
typical preferences are already present in infants (Baron-Cohen, 2005). Combining this theory
together with the EMB theory, the higher rate of autistic traits in individuals studying
systematic studies can be explained. Furthermore, in accordance with the EMB theory,
different studies also confirmed higher scores on the AQ in students of mathematics, physics
or engineering in comparison to students of humanity studies (Baron-Cohen et al., 2001). In
the study by Baron-Cohen et al. (2001), students of so-called systematic studies were much
more likely to reach a higher score on the AQ. Ridley et al. (2011) found a mean AQ score of
19.59 in systematic studies, compared to only 13.47 in students of humanities. This clearly
supports the importance of finding participants in the field of natural science studies, as these
individuals might be representing the autistic phenotype reaching into the normal population.
In sum, autistic traits can be found everywhere in the population, clinical or not.
Nevertheless, defining an autistic phenotype is a rather complicated matter. As well as the
whole spectrum disorder, the phenotype is of vast heterogeneity. Charman et al. (2011) point
out the important role of identifying the connection between heritability, neurocognitive and
biological development, and the behavior of the patient. Combined, this would lead to a better
understanding of the autistic phenotype. Moreover, identifying the different subtypes of the
spectrum is of great importance. Not only cognitively autistic individuals vary a lot, as in for
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example intelligence, but also their behaviors show immense diversities. Future studies must
concentrate on further investigation of the autistic phenotype and its expression, both
cognitively and behaviorally (Charman et al., 2011).
1.1.2 Facial processing in ASD.
Individuals suffering from autism spectrum disorder are restricted in their daily
routines in many ways. While some forms are rather mild, others can be extremely severe,
resulting in total isolation of the patient. Especially families and caregivers will experience
difficulties, as verbal and social interaction with the patient can be frequently impossible.
Since these deficits occur early in a patient’s life, a lot of symptoms are already apparent
before a diagnosis can be made. One of the characteristic symptoms is the general avoidance
of social and facial stimuli. In their 2005 study on gaze fixation, Dalton and colleagues came
to the conclusion that individuals with ASD show diminished gaze fixation and avoid looking
at faces. This, in turn, leads to overall less eye contact and diminished social interactions.
Different models have been proposed to explain the deficit in facial processing of
autistic individuals. In their article, Golarai, Grill-Spector, and Reiss (2006) introduce three
models explaining the facial processing deficit of individuals suffering from ASD. The first
model describes the phenomenon by a bottom-up effect caused by difficulties in low-level
visual processing, for example motion processing. This inability to process movements
accurately leads to problems in facial processing. A second model explains the deficit as a
consequence of a selected top-down ignorance and disinterest in human interaction. A third more neurological - model suggests that the responsible brain areas for facial processing are
less developed as a consequence of a smaller amount of time spent viewing faces. This could
have occurred due to either a bottom-up or a top-down effect. Additionally, a study in
Cambridge discovered that babies with lower levels of testosterone, as well as individuals
with a type E - hence ‘female’ - brain, show higher levels of eye contact (Baron-Cohen,
2005). This finding supports a connection between diminished facial processing in individuals
with ASD and the overrepresentation of male individuals in the clinical group.
Additionally, neuropathological research confirmed disruptions in certain brain areas,
especially the prefrontal cortex, the thalamus, the amygdala, the superior temporal sulcus, and
the fusiform gyrus (Baron-Cohen et al., 1999; Hall, Doyle, Goldberg, West, & Szatmari,
2010). Particularly the two latter areas are recognized to be involved in facial processing. An
alteration in signal or neurobiology in individuals with ASD gives strong reason for a
connection between brain alterations and cognitive and behavioral differences (Suda et al.,
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2011). Moreover, a connection to social anxiety seems to exist. Garner, Mogg, and Bradley
(2006) found that individuals suffering from social anxiety avoid looking at faces and social
stimuli in general. They suggest a problem in facial processing of these individuals. This can
be associated with distorted facial processing in individuals suffering from ASD (Golarai et
al., 2006). An additional explanation might be that faces as social stimuli elicit fear in patients
with ASD, as much as the presence of an overall deficit in basic emotional processing,
leading to avoidance of social interactions, and hence avoidance of interaction with faces
(Wilbarger, McIntosh & Winkielman, 2009). Already Kanner proposed anxiety as a
considerable factor in his original description of infantile autism (White, Oswald, Ollendick,
& Scahill, 2009).
Previous studies have focused on the activation of different brain structures in
individuals with ASD. In particular, the amygdala appears to show abnormal activation in
response to certain stimuli. The mid-brain structure is involved in rapid and automatic fear
processing and usually becomes activated when possible danger is processed, inducing a rapid
response - such as the fight-or-flight response (Golarai et al., 2006; Öhman, 2009). Moreover,
this structure is involved in the recognition of fear and shows neuronal abnormalities in
individuals with ASD (Baron-Cohen et al., 1999; Hall et al., 2010). Dalton et al. (2005)
discovered that individuals with ASD, who are fixating faces, show hyperactivation of the left
amygdala, hence putting forward a fear reaction. To avoid overarousal of fear-relevant brain
structures, avoidance of faces - which induce fear in these individuals - could lead to a
hypoactivation of the amygdala in general, as seen in the study by Dalton.
1.2 Startle Eyeblink Response
In addition to fMRI studies investigating the activation of the amygdala, physiological
studies are often used to examine the nature of fear reactions (Globisch, Hamm, Esteves, &
Öhman, 1999; Öhman, 2009; van den Hout, de Jong, & Kindt, 2000). Higher skin
conductance responses were observed in individuals with phobias while watching images
representing the feared object (Öhman, 2009; van den Hout et al., 2000). Similarly, startle
reflex modulation has gained much evidence in the last years regarding fear reactions.
Advantages of this measure are amongst other things the good temporal resolution (Åsli,
Kulvedrøsten, Solbakken, & Flaten, 2009), similar reactions across age and gender groups,
and the independence of language and voluntary actions (Wilbarger et al., 2009). Hamm,
Cuthbert, Globisch, and Vaitl (1997) reported a higher eyeblink magnitude, hence an
increased startle eyeblink response, in individuals with ophio- and arachnophobia watching
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pictures of snakes or spiders, respectively. Furthermore, the participants showed avoidance
behavior, represented in less time viewing the given picture. This parallels the behavior of
individuals with ASD, who avoid looking at social stimuli, such as faces, because these are
inducing fear, just like pictures of spiders induce fear in someone suffering from
arachnophobia.
Usually, avoidance behavior is expressed with heightened startle eyeblink responses in
healthy individuals toward unpleasant stimuli. The startle eyeblink response is enhanced by
negative events and reduced by positive stimuli in comparison to control objects (Dichter et
al., 2010). A loud noise for example is interpreted as a threatening situation and a startle
eyeblink response occurs. Positive events associated with the startle probe (noise) usually
reduce this automatic reflex. The startle eyeblink response is generally intact in individuals
with ASD, hence giving the possibility to test affective reactions in a group of patients
(Wilbarger et al., 2009). Negative events coupled with an aversive noise should elicit higher
startle responses, while positive events paired with noise should reduce the startle effect in
both healthy and autistic individuals.
As in the study of Wilbarger et al. (2009), Dichter, Benning, Holtzclaw, and Bodfish,
(2010) investigated the startle eyeblink response of individuals with ASD to pictures of
different valence in comparison to neurotypical participants. The EMG results suggested an
enhanced startle eyeblink response to positive stimuli for the ASD group. The diminished
response to unpleasant stimuli did not reach significance. Moreover, the study demonstrated
an enhanced postauricular reflex to unpleasant pictures, stating an exaggerated avoidance
response, measured behind the ear (pulling back of the ear). Dichter et al. (2010) concluded
that deficits in emotional informational processing are present in individuals with ASD,
consistent with the findings of Wilbarger et al. (2009). Nevertheless, studies concerning the
startle eyeblink response in reaction to facial stimuli are generally fairly contradictive (Alpers,
Adolph, & Pauli, 2011). While enhancement of the startle eyeblink response to negative
scenes has become obvious in many studies, there is still a lot of uncertainty about the
influence of the emotion expressed in facial pictures. Alpers et al. (2011) explain this
discrepancy by higher emotional arousal of scenes, while facial expressions do not create this
high level of arousal in the viewer, leading to diverse results.
The present study is focusing on the startle eyeblink response, triggered by an acoustic
probe of white noise. Startle responses are commonly tested in affective or attention measures
(Flaten, Nordmark, & Elden, 2005). The latency of an acoustic startle is relatively short with
about 6-8 msec. Operating as a startle center, especially the nucleus reticularis pontis caudalis
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(nRPC) located in the pons, is thought to be the main structure involved in the response. This
is supported by the finding that a startle response can be elicited by electrical stimulation at
this site (Lee, López, Melone, & Davis, 1996). The nRPC is connected to the muscles around
the eye controlling the eyeblink reflex. Furthermore, input from the amygdala is received here
(Dichter et al., 2010). Since there is a connection between the amygdala and startle response
amplitude, an abnormal startle eyeblink response in individuals with ASD could moreover
indicate a dysfunction of the amygdala as pointed out previously (Wilbarger et al., 2009).
1.3 Hypotheses
Given that individuals suffering from ASD show abnormal gaze patterns when
processing faces (Dalton et al., 2005), and that previous studies showed abnormalities in the
neurology of autistic individuals (Golarai et al., 2006), autistic individuals are expected to
express more anxiety when processing faces. Consequently, an enhanced startle eyeblink
response to facial objects can be expected. The assumption that an autistic phenotype exists
and extends far into the non-clinical population, leads to the presumption that the group
scoring high on the autism spectrum quotient questionnaire will show an increased startle
eyeblink response magnitude in response to social stimuli, in this case faces. As a result, the
first hypothesis is as follows:
Hypothesis 1: The high scoring group on the AQ is more likely to show increased startle reflexes
when viewing social stimuli/faces, due to elicited fear.
Wilbarger et al. (2009) demonstrated that fear reactions in autistic individuals are
unconscious and found out that individuals with ASD do not differ from healthy individuals
in a subjective measure of fear. With a visual analogue scale (VAS), where subjective feelings
regarding valence and arousal levels can be indicated, emotion recognition can be measured.
Autistic participants in the study by Wilbarger et al. (2009) recognized the right emotions,
consistent with those of healthy individuals, yet showed enhanced fear reactions indicated
objectively by the startle eyeblink response to stimuli not indicated as fear inducing in the
subjective measurement. Based on that study, valence and arousal ratings are expected to
show no difference between the groups, pointing to an unconscious mechanism of fear.
Hypothesis 2: No difference is expected between the experimental and the control group in the
subjective ratings of valence and arousal.
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The principle of the startle eyeblink response is based on the fact that fear reactions
elicit higher eyeblink responses - as a form of the fight-or-flight reflex. Fear is expressed
automatically. Accordingly, negative events or pictures elicit a higher startle eyeblink
response, while positive events or pictures diminish the response (Dichter et al., 2010).
Taking this as a starting point, a difference in startle magnitude to the different emotions
shown in the stimuli pictures is expected in the present study.
Hypothesis 3: A difference in startle magnitude between the different emotions is expected.
1.4 Relevance
The present study aims at investigating the cognitive and affective nature of face
processing in students with autistic traits by measuring the startle eyeblink response. Some
studies have been conducted in this field of research, investigating emotional processing in
children and adolescents with ASD (Dichter et al., 2010; Wilbarger et al., 2009); however, the
field of research is new and further support of existing theories is of great importance. Since
the spectrum of the disorder can range widely and symptom expression is of high
heterogeneity, it is important to extend investigations of the effect into the non-clinical
population. The autistic phenotype is of vast diversity and autistic traits can be seen in, for
example, a student population. Considering that even students can express distorted social
behavior or experience similar developmental problems typical for individuals with ASD, it is
of high relevance to identify the problems and restrictions in daily life. If it can be established
that a certain amount of students are showing enhanced incidences of autistic traits, further
investigations in this field will have to be made. With this, an understanding of the wide
spectrum of ASD can be better understood and social support can be established for
individuals affected. Consequently, this will help doctors, psychologists, parents and
caregivers to improve in the field of dealing with the disorder. Specialized therapies can be
developed to make life easier for patients and their families.
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COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
2 Method
2.1 Participants
To recruit participants, flyers were hung up at different faculties of the University of
Tromsø, Norway, with focus on the natural science faculty. After early drop-out of one
participant, 40 students between 19 and 31 years participated in the study (M = 22.96, SD =
2.698 for age). Twenty-two participants were male. The participants were divided into two
age-controlled groups, the experimental group scoring 17 or higher on the AQ and the control
group scoring below 17, resulting in 14 participants representing the experimental group high
in autistic traits and 26 participants low in autistic traits. The latter served as the control
group. Freitag et al. (2007), who evaluated a short edition of the German version of the AQ
(AQ-k) as a screening instrument, came to the conclusion that a threshold of 17 is reasonable
in screening neurotypical individuals for autistic traits. This cut-off score was adapted for the
present study to achieve a realistic division into two groups. The mean AQ score was 15.1
(SD = 5.261) for the 40 participants.
Table 2
Demographics of all Participants per Gender
Gender
Male
Female
N
Minimum Maximum
M
SD
Age
22
19
26
22.36
2.172
AQ
22
5
27
16.05
5.753
Age
18
20
31
23.67
3.144
AQ
18
5
20
13.94
4.478
Note. SD = Standard Deviation.
2.2 Materials
2.2.1 EMG/picture presentation.
To record the strength of the startle eyeblink response, surface-electrodes were
attached to the muscle under the right eye, a muscle called ‘orbicularis oculi’. These
electrodes recorded the electromyographic (EMG) activity in comparison to a control
16
COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
electrode adjusted to the forehead (Hamm et al., 1997). White noise of 95dB was presented
over headphones during picture presentation. Acoustic probes were semi-randomized and
occurred at one out of three given points in time after picture onset (2.5, 3.5 or 4.5 seconds
after onset). No same latency occurred more than twice after each other. With this, different
latencies of responses could be accounted for. Five acoustic probes were presented before first
picture onset, so that participants got habituated to the noise. The acoustic probe was
presented with picture display, hence occurring while the participants were viewing the object
on a screen. Some control noises were presented during a black screen, functioning as
baseline stimuli. To ensure that participants paid attention to the presented images, a web-cam
had been installed next to the screen, so that the whole session could be followed from the
experimenter’s room. Twenty-seven different pictures were presented randomly on a
computer screen in front of the participant. All of these pictures were appearing twice in each
session, so that a total number of 54 images were shown. Picture presentation of one set of all
pictures took about 20 minutes. The pictures represented facial images (photographs) showing
six happy, six fearful, six angry and six neutral emotional faces, each seen out of two different
angles. One direction was a frontal view of the faces; the other a 45° sideways turned
photograph showing the face from the left-hand side. Three neutral control images,
representing objects, appeared randomly as control variables. Pictures were taken from the
Karolinska Directed Emotional Faces set (KDEF; Lundqvist, Flykt, & Öhman, 1998),
originally consisting of 4900 standardized emotional facial pictures, showing different
emotional reactions. Four out of seven original emotions were selected (happy, fearful, angry,
and neutral), presented out of two angles (original dataset consisting out of five angles).
Cultural validity was met due to the objectiveness of the measurement. Therefore, no
influence on the measurement was expected due to the different nationalities of the
participants.
2.2.2 SAM/VAS subjective measure.
To test the difference between objective and subjective feelings of fear, the Self
Assessment Manikin (SAM; Bradley & Lang, 1994) in combination with a visual analogue
scale (VAS) was given after the experimental session. Participants indicated on a continual
line (VAS) how much arousing/calming and positive/negative they experienced each of the 27
pictures seen before in the EMG session. Pictures were presented again and participants could
individually decide for how long they wanted to see each of the pictures. After that, the VAS
appeared and indication could take place via mouse click. Images (SAM) helped to identify
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COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
the right emotions. Those images might especially be of importance when verbal IQ is in a
lower range, so that identification of the right answer is easier than when answers have to be
read. The subjective measure was done because fear reactions can often be unconscious
(Wilbarger et al., 2009). If so, the subjective measurement of fear should not show any
differences in fear ratings between the two groups.
2.2.3 Autism spectrum quotient questionnaire.
The last test to be conducted in the testing session was the autism spectrum quotient
questionnaire (AQ), a self-administered forced-choice 4-point scale questionnaire, containing
of 50 items. Skills like attention switching, imagination ability, social skills, communication
skills, and attention to detail are assessed by the AQ. Only the latter category is known to be
improved in individuals with ASD, while the other four categories are generally
underdeveloped in patients (Baron-Cohen et al., 2001). The AQ has been found to be an
efficient tool for assessing the autistic phenotype in a non-clinical population (Wheelwright,
Auyeung, Allison, Baron-Cohen, 2010). Participants indicated on a scale if they strongly
agreed, slightly agreed, slightly disagreed or strongly disagreed with the given statement.
Presence of the autistic trait was scored with 1, absence with 0, such that total scores could
range from 0 to 50. For Norwegian students the Norwegian version of the AQ was used, for
international students the original English version was given to avoid misunderstandings due
to language (Baron-Cohen et al., 2001).
2.3 Procedure
After signing the informed consent, participants sat down on a comfortable chair in the
testing room in front of a computer screen. The experimenter again instructed participants
about the procedure, the duration, and nature of the experiment. The importance of following
the pictures at all times was especially emphasized. Three electrodes were prepared with twosided tape and gel. The skin below the orbicularis oculi muscle under the right eye and on the
forehead was cleansed and the electrodes attached. As soon as the participants’ eyes got
habituated to the electrodes, headphones were placed over the ears, the web-cam placed in the
right position, and instruction to look at the screen while picture presentation was given once
more. The computer screen was switched on and the experimenter left the room. In the
experimenter’s room the test program was started after validating and controlling the sound
settings. The pictures appearing on the test screen could also be followed on the
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COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
experimenter’s screen as well as the video from the web camera, so that errors in presentation
could directly be detected and adjusted.
After completing the EMG session, participants were taken to the experimenter’s
room, seated in front of another computer screen, where the subjective measure (VAS/SAM)
was carried out. Instructions were given on screen and by the experimenter. Following the
subjective test, participants answered to the 50 statements of the AQ by indicating one point
on a 4-point response scale (strongly agree, slightly agree, slightly disagree, or strongly
disagree). Participant’s help was compensated with two lottery scratch tickets, worth 50
Norwegian Crowns (~ 8 US $).
2.4 Apparatus and EMG
EMG activity was recorded with three sintered-pellet silver chloride AgCl miniature
surface electrodes of 4 mm diameters, filled with Microlyte electrolyte gel (Coulbourn
Instruments). Two electrodes were attached to the skin at the right orbicularis oculi with an
interdistance of around 1.5 cm, while the control electrode was placed in the middle of the
forehead. The EMG signal was amplified by a factor of 50000 and filtered (8-1000 Hz) by a
Coulbourn V75-04 bioamplifier. The signal was further integrated with a Coulbourn V76-24
contour-following integrator with 10 ms constant. On a LabLinc V interface on a connected
computer the output was recorded (100 ms before until 200 ms after stimulus presentation).
Noise stimuli lasted 50 ms and were presented at 95 dB over Sennheiser HD 250 headphones.
Different latencies of noise presentation were accounted for in semi-randomized order.
2.5 Data Analysis
Since the differences in reactions of the group scoring high on autistic traits in contrast
to the group scoring low on the AQ, plus the individual differences within the groups, were
investigated, the data was analyzed with repeated-measures analysis of variance (ANOVA).
This statistical method accounts for the between-subject variable measuring the differences
between the two groups tested (high versus low scoring group) and the within-subject variable
which measures the differences in startle eyeblink response between individuals within one
given group. Therefore, the between-subject design explained whether there was a significant
effect in startle eyeblink response between the different groups, for example if the high
scoring group truly showed enhanced startle responses to faces (hypothesis 1). The withinsubject component explained the differences within each group. A repeated-measures
ANOVA combines these factors in one analysis. The analysis was done for the EMG session
19
COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
and the subjective measure individually. The advantage of a within-subject design is the
reduction of variability and an increased power to detect significant effect.
To measure the dependent variable startle magnitude, the different emotions compared
with the baseline object were used as a 4-level within-subject factor. A 2-level within-subject
factor for direction was added. As a between-subject factor the low and high scoring groups
on the AQ were used.
3 Results
3.1 Autism Spectrum Quotient Questionnaire
The scores of the AQ showed large variations between the 40 participants (M = 15.10,
SD = 5.261), supporting the view of an autistic phenotype reaching into the normal
population. The participants’ scores ranged from 5 (very low autistic traits) to a score of 27,
reaching as high as the cut-off score for autism spectrum disorder mentioned in another study
(Woodbury-Smith, Robinson, Wheelwright, & Baron-Cohen, 2005).
Twelve participants had to be excluded from further analysis because they were
drinking coffee during the three hours prior to the experimental session. The startle eyeblink
response is known to be influenced by caffeine, which has lead to exclusion of these
participants in the present study (Mikalsen, Bertelsen, & Flaten, 2001). After exclusion of the
given participants from further analysis, 12 high scoring and 16 low scoring individuals were
included. Seventeen of the 28 participants were male. The mean score of the AQ after
exclusion was 16.04 (SD = 5.31) with a mean age of 22.57 (SD = 2.69) for the 28 participants.
3.2 Ratings
The subjective SAM/VAS measure showed a significant difference in valence ratings
of the different emotions (F (8,240) = 62.844, p < .001). Happy faces from either side were
rated more positively than neutral, fearful and angry faces. Objects were rated having neither
positive nor negative value. For the valence rating no difference between the groups was
found (F (8,232) = .205, p = .99). All emotions elicited the same ratings of
positivity/negativity, independent of the AQ score.
As for the valence ratings, arousal levels of the SAM/VAS also reached significance
(F (8,240) = 31.775, p < .001). Higher arousal levels were elicited by angry and fearful faces
from either direction, in comparison to rather low activation by neutral, happy and object
20
COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
stimuli. Equally to the subjective valence scores, ratings of arousal did not differ between the
high and low scoring group (F (8,232) = 1.17, p = .32).
3.3 Startle Eyeblink Response
Contrary to the prediction of higher startle eyeblink response to facial stimuli for the
group high in autistic traits, no significant difference was found in comparison to the control
group. The repeated-measures ANOVA did not reach significance for the between-subject
effect of high against low AQ groups, F (1, 26) = .035, p = .853. Overall, the high scoring
group showed rather a diminished startle eyeblink response to all stimuli. Startle eyeblink
response to objects was used as a baseline. Table 3 summarizes F-scores and p-values of the
repeated-measures ANOVA.
Table 3
Within-Subject Analysis for Emotions, Direction, and All Interaction Effects
with the Between-Subject Variable AQhigh
Effect
Mean Square
F
Sig.
emotions
0.254
2.451
0.106
Emotions · AQhigh
0.034
0.581
0.535
direction
0.524
12.873
0.001*
Direction · AQhigh
0.002
0.046
0.832
Emotions · direction
0.188
2.078
0.134
emotions·direction·AQhigh
0.035
0.392
0.683
Note.*significant at .005 level.
Nevertheless, a clear significant difference between the different angles of
presentation was found (F (1, 26) = 12.873, p = .001). Frontal presentation of the pictures led
to higher overall startle eyeblink responses in both groups. Presentation from the side resulted
in lower magnitude and reduced difference between the dissimilar emotions, especially for the
high scoring group (see figure 2). Furthermore, there was a difference in startle activation
between the four emotions (F (7,203) = 2.339, p = .0257), confirming hypothesis 3. A post-
21
COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
hoc Tukey test revealed significant differences between angry frontal and fearful frontal, and
neutral sideways and fearful frontal picture presentations.
Figure 2: Startle eyeblink responses for all four emotions for both groups with frontal (left)
and angular (right) picture presentation
4 Discussion
In the present study the startle eyeblink response to social stimuli in students with high
autistic traits was assessed. No confirmatory evidence could be found for hypothesis 1, stating
that higher startle eyeblink response to facial stimuli would be observed for the group scoring
high on autistic traits. There was no difference in startle magnitude between the two groups.
Hypothesis 2, maintaining that no difference between the groups for the objective
measures should be expected, could be confirmed. The ratings of valence and arousal were
the same regardless of AQ score.
The third hypothesis, holding that there is a difference in startle eyeblink response
between the different emotions presented, could be confirmed. Pictures representing fear from
a frontal perspective elicited higher startle than frontal angry or neutral sideways facial
expressions. Moreover, a difference between the different angles of picture presentation was
found. Pictures seen from the front resulted in higher startle eyeblink responses than pictures
seen from a 45° angle from the side. Subsequently, the results will be discussed.
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COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
4.1 Hypotheses revisited
Students high in autistic traits did not show an enhanced response to social stimuli in
comparison to the control group. Consequently, hypothesis 1 could not be confirmed.
Nevertheless, the finding is consistent with the overall picture of the current research in this
new field. Hypotheses and results regarding startle eyeblink response in individuals with ASD
are contradicting and different theories exist (Alpers et al., 2011). Bernier, Dawson,
Panagiotides, and Webb (2005) examined the two hypotheses of enhanced versus diminished
fear reactions due to under- versus over-responsiveness of the amygdala. As in the present
study, they came to the conclusion that there was no difference between the experimental and
control group. The same conclusion was drawn by Salmond, de Haan, Friston, Gadian, and
Vargha-Khadem (2003) who did not find any difference in startle eyeblink response to nice
and scary pictures between autistic children and to the neurotypical group.
There are several reasons for the fact that no difference was found between the two
groups. First of all, the before mentioned range of diverse results suggests that in this young
field of research no clear picture of results exists yet. As for the different emotions, results
vary for the startle eyeblink response between ASD and control groups. In addition, Alpers et
al. (2011) explain the difference not by the valence, but arousal of the different pictures. They
claim that higher arousing pictures lead to higher startle responses, regardless of the valence
of the picture. Their study results show higher startle responses to both positive and negative
pictures with highly arousing level, in comparison to low arousing pictures of either valence.
A lower startle response of individuals with ASD was explained by a greater alertness of
healthy individuals. Regarding this conclusion, the current study shows similar results, with
no difference between the experimental and control group, but a tendency to overall lower
startle responses in the high scoring AQ group.
As predicted and confirmed by Wilbarger et al. (2009), patients do not differ from a
neurotypical group in subjective measures of valence and arousal. The difference in startle
eyeblink response found in that study was explained by an unconscious process for objective
measurements. The present study found that recognition of emotional and facial stimuli is
normal in individuals scoring high on the AQ, indicated by no difference in valence and
arousal ratings between the two groups. Wilbarger et al. (2009) drew the same conclusion for
their sample of patients with ASD. The two different groups used in the two studies might not
be comparable without any deduction. However, the present results point toward the direction
of an autistic phenotype reaching into the normal population with comparable results to those
found in individuals suffering from ASD. Moreover, the results of the subjective
23
COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
measurement confirm that identification of the different emotions is intact and equivalent in
the two groups. The fact that hypothesis 1 could not be confirmed is therefore not due to a
defect in emotional processing, but possible cognitive processing distortions as predicted by
Wilbarger et al. (2009). The presence of aberrant cognitive processes has to be investigated in
future studies.
The finding that the different emotions differed significantly from each other is
consistent with the study by Anokhin and Golosheykin (2010) who investigated the reaction
to fearful faces, which elicited higher startle response than neutral or happy faces. However,
they did also find higher startle to angry faces, which could not be confirmed by the present
study. In contrast to another study which found higher startle eyeblink response to angry than
to fearful faces (Springer, Rosas, McGetrick, & Bowers, 2007), the opposite was found in the
current study. A lot of mixed results exist in this field of research and further investigation
will be of importance. Especially, the direction of picture presentation has gained little
attention in previous studies. As it has been found in the present study, direction of picture
presentation influences the startle eyeblink response. Future studies should thus account for
different angles of direction in picture presentation. Nevertheless, the current results are
corresponding with the theory that negative images elicit higher startle responses in
comparison to positive or neutral stimuli regardless of AQ score (Dichter et al., 2010).
The effect that different angles of presentation lead to a significant difference in startle
eyeblink response has not been investigated by any study before. Frontal presentation elicited
greater startle eyeblink response in the present study than images presented in a 45° angle
from the left side. An explanation for this finding might be that frontal presentation leads to a
rather direct confrontation with the face presented. Therefore, participants feel more
addressed by the person in the picture and reactions are more intense. Such as, if an angry
face is facing the participant directly, fear reactions increase in comparison to a face just seen
from the side and hence not addressing the participant her- or himself directly. That is
comparable to the results of the study by Sabatinelli, Bradley, and Lang (2001), who found
that startle responses increased when participants were anticipating instead of just watching
pictures. Anticipating - or awaiting - a stimulus can be compared to a more direct connection
to the picture, as it is expected. This might lead to a stronger link between the participant and
the upcoming picture. The same occurs with the different angles of presentation, with facial
images confronting the participant more directly, leading to an increased emotional reaction
in the participant. The anticipating effect was especially present for positive pictures.
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COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
4.2 Limitations
Different studies have confirmed that autistic individuals generally avoid looking at
faces show a hypoactivation of the amygdala and related brain structures (Dalton et al., 2005),
and show different patterns of fear reactions regarding social stimuli (Dichter et al., 2010;
Wilbarger et al., 2009). Regarding altered neurobiological structures and mechanisms, Dichter
et al. (2010) found, that especially the amygdala is involved in the deficits experienced by
individuals with ASD. As the amygdala is involved in fear reactions, an altered neurobiology
of this brain structure can account for distorted fear reactions. Furthermore, removal of the
temporal lobe and amygdala in primates showed symptoms paralleling social deficits found in
autism (Wilbarger et al., 2009). These brain structures can also directly influence the startle
response. An enhanced startle eyeblink response in individuals with ASD has been found to
positive images in the study by Dichter et al. (2010). On the other hand, Wilbarger et al.
(2009) did not only find an increased startle eyeblink response, thus higher expression of fear,
to positive but to negative stimuli as well. The authors interpreted these results as an indicator
of increased defensive system activity in individuals with ASD. The results of the present
study are not consistent with these findings; however, the studies described used children with
a diagnosis of ASD, while in the current study healthy individuals were examined. Moreover,
limitations of the given studies are that different age groups were used, including control and
experimental group representing different ages. Additionally, not the same set of pictures as
emotional stimuli were used in the studies, which can contribute to dissimilar reactions,
especially regarding negative images (Wilbarger et al., 2009). In particular, the selection of
facial stimuli pictures plays a major role in distinguishing fear reactions of patients and
normal controls. Additionally, the differences in viewing time can contribute to further
disparities in the results (Wilbarger et al., 2009).
Another limitation results from the fact that individuals with ASD have a general
impairment in mimicry, mutual gaze, and patterns of face viewing, which could result in
unusual perception of the given stimuli (Golarai et al., 2006). Therefore, patients might not
even recognize the valence of pictures due to uncommon gaze patterns. The limitations
present in other studies can be further extended to the present study, consistent with the fact
that varying results are found across different studies. The startle eyeblink response varies in
different experimental settings, and higher startle has been found to positive, negative or both
images. This stresses the importance of further investigation in this field of research, to come
to reliable results regarding the nature of fear reactions to facial stimuli in ASD and the
autistic phenotype.
25
COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
Moreover, the present study has some further limitations. First of all, the sample size
was not very large and after data reduction only 28 participants could be included in final
analyses. Future studies should increase sample size to reach a better basis for generalizations.
Unfortunately, the participant with the highest score on the AQ had to be excluded from all
analyses due to early drop-out. More participants representing the high scoring group could
possibly have changed the results. Furthermore, a generalization to individuals diagnosed
with ASD can cause problems. The research field of an autistic phenotype is still in its
fledgling stage and no clear results exist whether and how a connection between ASD and the
normal population high in autistic traits is present. However, some studies have investigated
important features and connections in this young field of research, and with further
investigations a better understanding of the nature of ASD and its spectrum into the normal
population can be achieved. In addition, results might have been biased by gender effects.
Differences in gender were not accounted for and the general higher amount of male
participants in the high scoring group could have lead to lower startle magnitude. Anokhin
and Golosheykin (2010) found a gender difference in their study, with females expressing a
general higher startle eyeblink response than males. In combination with the extreme male
brain theory it is reasonable that more males are scoring high on the AQ. The results however
showed no difference in startle magnitude in comparison to the control group. The control
group had an overall higher, though not significant, magnitude of EMG signals, which could
thus be explained by the overrepresentation of females in this group. However, this
hypothesis should be further investigated to draw any reliable conclusions.
To sum it up, most studies show varying results regarding the startle eyeblink response
in individuals with ASD. Findings span from increase to negative, positive or both picture
valences to no difference between the experimental and control group, as found in the present
study. It has to be further investigated how startle eyeblink responses are affected by the
valence of pictures for individuals suffering from ASD or those high in autistic traits. While
diagnosis of ASD can be made fairly easily today, the nature and treatment of this severe
disorder has to be further explored. Especially, the spectrum which seems to reach into the
neurotypical population needs further investigation and will be of importance for a better
understanding of this heterogeneous disorder. Autism spectrum disorder is still a young
research field, and a lot of studies will be required to fully understand its nature and find
better treatment techniques. If we can understand the social deficits these individuals are
26
COGNITIVE AND EMOTIONAL PROCESSING OF SOCIAL STIMULI IN STUDENTS WITH AUTISTIC TRAITS
experiencing – especially regarding facial processing and fear reactions – caregivers,
psychologists and patients can benefit from that.
5 Conclusion
The general symptoms of ASD such as disturbances in non-verbal communication
skills, social interactions and the expression of stereotyped behaviors can be found in virtually
every patient (American Psychiatric Association, 2000). However, the expression of the
syndrome varies vastly between individuals, and the disorder is highly heterogeneous. In this
way, the spectrum can reach far into the neurotypical population and autistic symptoms can
be observed in individuals not diagnosed with any form of ASD. All symptoms vary on a
spectrum and can have expressions from a severe to a mild degree. The avoidance of eye
contact and faces can be linked to diminished social interactions in general.
The hypothesis of higher startle eyeblink responses in individuals scoring high on the
AQ could not be confirmed. There were no differences between the two groups. The second
hypothesis that there is no difference between the groups for the subjective measurement
could be confirmed. Valence and arousal of the different emotions was experienced in the
same way for groups scoring high and low on the AQ. The third hypothesis, that different
emotions elicit varying magnitudes of startle eyeblink responses, has been confirmed - with
fearful faces presented frontally leading to an increased startle eyeblink response in
comparison to angry frontal and neutral pictures presented from the side. In addition, a
significant difference was found between the different angles of picture presentation. Frontal
presentation elicited higher startle eyeblink responses in comparison to presentation from a
45° angle.
Overall, the existence of an autistic phenotype reaching into the non-clinical
population could be shown. Fear reactions to facial stimuli appear to be comparable to those
expressed by the neurotypical population. However, findings are contradictive in this young
field of study and future studies will show how fear reactions to social stimuli are affecting
individuals suffering from ASD. It will be of importance to account for the wide spectrum of
the disorder as put forward by the present study.
27
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