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APPLIED COGNITIVE PSYCHOLOGY
Appl. Cognit. Psychol. (2010)
Published online in Wiley InterScience
(www.interscience.wiley.com) DOI: 10.1002/acp.1657
When’s Your Birthday? The Self-reference Effect in
Retrieval of Dates
CLARE J. RATHBONE* and CHRIS J. A. MOULIN
Leeds Memory Group, Institute of Psychological Sciences, University of Leeds, UK
SUMMARY
Material encoded with reference to the self is better remembered. One interpretation of this effect is
that the self operates to organise retrieval of memories. We were motivated to find out whether this
organisational principle extended to everyday information and for material not explicitly related to
the self. Participants generated friends’ birthdays from memory and then gave their own birthday. We
found that participants were particularly likely to recall birthdays from on or around the date of their
own birthday. Thus, memory for birthdays clusters around self-relevant information, even when there
is no specific attempt to recall self-related material. Birthdays clustered somewhat around the time of
testing, important dates in the calendar, and for a close other, but not to the extent of the participants’
birthdays. We suggest this is a demonstration of the organisational structure of the self in memory.
Copyright # 2010 John Wiley & Sons, Ltd.
The self-reference effect (SRE; Rogers, Kuiper, & Kirker, 1977) refers to the robust
phenomenon that things encoded with reference to the self are generally remembered
better. For example, words that are rated for how much they describe one’s self are later
better recalled than words rated as descriptions of another person (e.g. Symons & Johnson,
1997). This finding supports theories that view the self as a mechanism through which
memories are organised, stored and retrieved (e.g. Conway & Pleydell-Pearce, 2000), and
emphasises the rich and highly elaborated structure of the self as a schema in long-term
memory. The mechanisms behind the SRE are thought to be related to the encoding
specificity hypothesis (Tulving & Thompson, 1973), which states that memory
performance is improved when encoding conditions match retrieval demands. Symons
and Johnson (1997) suggest that self-referential processing might have such a powerful
effect on memory as the self is a well-developed cognitive structure that promotes the
organisation and elaboration of knowledge, thus promoting compatible retrieval and
encoding conditions.
It has previously been suggested that the SRE does not necessarily reflect a unique or
special effect of the self. For example, Klein and Kihlstrom (1986) found that preferential
retrieval in the self-reference condition could be explained by a process of elaborate
encoding, and suggested that any task in which items are encoded with reference to a highly
elaborate and organised structure (such as, but not limited to, the self) will improve recall.
*Correspondence to: Clare J. Rathbone, Leeds Memory Group, Institute of Psychological Sciences, University of
Leeds, Leeds LS2 9JT, UK. E-mail: [email protected]
Copyright # 2010 John Wiley & Sons, Ltd.
C. J. Rathbone and C. J. A. Moulin
In line with this proposal, Bower and Gilligan (1979) found an SRE when both self and
mother were used as the referent. Bower and Gilligan proposed that encoding with
reference to the non-self-schemata of any well-known person will produce preferential
retrieval, and that the SRE is a product of depth of processing, rather than necessarily an
effect of reference to the self. Gillihan and Farah (2005) suggested that many studies that
seek to examine whether self-processing is unique are flawed by differences between task
demands in self and other conditions. Such confounds make it hard to extrapolate the
potential uniqueness of self as a cognitive structure. The present study avoids such
problems by employing a straightforward recall task that is not explicitly related to the self.
The self is also suggested to play an organisational role in the temporal distributions of
memories. Many researchers have investigated the strategies people use to date events, and
the temporal associations that might link memories (e.g. Betz & Skowronski, 1997; Brown,
1990; Linton, 1986; Thompson, Skowronski, Larsen, & Betz, 1996). A prominent field of
research that focuses on the temporal distribution of memories deals with the reminiscence
bump: The phenomenon that adults tend to recall memories best from the period of late
adolescence and early adulthood (e.g. Glück & Bluck, 2007; Jansari & Parkin, 1996;
Rubin, Rahhal, & Poon, 1998; Rubin, Wetzler, & Nebes, 1986). This robust effect has been
demonstrated using a variety of methodological approaches (although the exact location of
the bump varies depending on method, see Rubin & Schulkind, 1997), and cross-cultural
investigations indicate it to be a universal phenomenon (e.g. Conway, Wang, Hanyu, &
Haque, 2005). The reminiscence bump has been found for public new events (Holmes &
Conway, 1999), age of encountering favourite films (Sehulster, 1996), books (Larsen,
1996) and songs (Holbrook & Schindler, 1989). Furthermore, reminiscence bumps have
been found for both episodic and semantic memories (e.g. Rybash & Monaghan, 1999).
There are several different theories behind the reminiscence bump, including cognitive,
biological and identity-based accounts (for a review, see Rubin et al., 1998). Identity-based
accounts suggest that the reminiscence bump is linked to the development of a stable,
coherent self (e.g. Cappeliez, 2008; Conway & Haque, 1999; Conway & Holmes, 2004), a
process that is thought to occur during this period in the lifespan (Erikson, 1950; Fitzgerald,
1988). In support of accounts that view the self as central to reminiscence bump formation,
research has also shown that memories across the lifespan cluster around times relevant to
the self. For example, Rathbone, Moulin, and Conway (2008) found that self-images (such
as ‘I am a mother’) were linked with sets of highly accessible episodic memories from the
time that self-image was judged to emerge. In effect, this finding reflects a SRE in the longterm encoding and retrieval of memories. Times of central importance for the self are
associated with heightened retrieval.
The current study used a novel approach, bridging research on the standard SRE
(typically assessed using word-list methodologies; for a review see Symons & Johnson,
1997) and the reminiscence bump literature on the centrality of self in encoding and
retrieval (e.g. Conway, 2005). If the self plays an executive role in long-term memory
organisation, then we would expect retrieval of friends’ birthday dates to show a clustering
effect: We would better remember birthdays matching, or close to, our own. Other research
has considered birthday distributions; the Birthdays Paradox refers to the counter-intuitive
finding that there is a 50% probability for any two people in a group of 23 sharing a birthday
(e.g. McKinney, 1966). The present study focuses not on the probability that any two
people will share the same birthday, but on the probability that birthdays recalled by a
person will match, or be close to, their own birthday. The probability of one birthday
matching any specified birthday is in fact much lower than the McKinney value. The aim of
Copyright # 2010 John Wiley & Sons, Ltd.
Appl. Cognit. Psychol. (2010)
DOI: 10.1002/acp
Self-reference effect for dates
this study was to investigate the distribution of recalled birthday dates around date of own
birthday. If the self acts as an elaborative schema through which memories for dates are
organised, we would predict a peak in retrieval for dates close to the date of one’s own
birthday.
METHOD
There were 2455 participants (mean age ¼ 23.6, SD ¼ 8.86; mode ¼ 19; median ¼ 22,
range ¼ 12–95), who completed an online questionnaire (a further 636 participants
submitted questionnaires that were too incomplete for use, e.g. no birthdays recalled). The
questionnaire asked for as many birthday dates (day and month) as could be recalled,
up to a maximum of 24. The questionnaire was active from 18 December 2007 to
18 February 2009, and was linked from several psychology survey websites associated
with both American and Swiss universities.1 Students at the University of Leeds (UK) also
completed the questionnaire for course credits, thus our sample was likely a cross section
of different western nationalities. No data on nationality, IP address, or completion time
was recorded. Participants were instructed to provide dates for friends and not family
members, and to avoid guessing. Participants were also asked to rate their closeness to each
friend by ranking them as 1 (not close), 2 (quite close) or 3 (very close). At the end of the
questionnaire, participants gave their own date of birth. All friends’ birthday dates were
entered on the same screen, however there was a separate final screen for entry of the
participant’s own birthday.
RESULTS
Participants recalled a total of 21 721 birthdays, generating dates for a mean of 8.83 friends
(SD ¼ 6.09; range ¼ 1–24). Participants’ own birthdays were distributed equally across the
year (Figure 1). This was analysed statistically by calculating the number of birthdays that
fell into each calendar month and comparing this with the expected number per month
(total birthdays divided by 12 ¼ 205) in a one sample t-test (t ¼ ".9, df ¼ 11, p ¼ .93). The
mean count of birthdays recalled across the year by day was 59.5 (SD ¼ 14.6).
To analyse whether clustering occurred for retrieval of birthdays around date of own
birthday, friends’ birthdays were recoded as number of days from the participant’s own
birthday. As shown in Figure 2 (upper left panel) they clustered around day zero (the
participant’s birthday). To analyse we generated an even distribution, reflecting the null
hypothesis based on equal distribution of birthdays across all dates (i.e. the mean number of
birthdays and the SD of dates as recoded around birthday ¼ 26.5). It was then possible to
examine the observed count with reference to this mean and standard deviation as a z-score.
The distribution around own birthday demonstrates a significant peak at 0 (own birthday)
of 429 counts compared to the expected frequency of 59.5 (z ¼ 13.94). This pattern
suggests that memory for birthdays is temporally organised with reference to the self, much
like episodic memories (Rathbone et al., 2008).
1
Thanks to the websites which added a link for the Birthdays Study: http://www.socialpsychology.org/expts.htm,
http://genpsylab-wexlist.unizh.ch/, http://psych.hanover.edu/research/exponnet.html.
Copyright # 2010 John Wiley & Sons, Ltd.
Appl. Cognit. Psychol. (2010)
DOI: 10.1002/acp
C. J. Rathbone and C. J. A. Moulin
Figure 1. Distribution of participants’ own birthdays across the year
Figure 2. Distribution of recalled birthdays around date of own birthday as zero (upper left panel),
around date of test as zero (upper right panel), across the year around Christmas day as zero (lower
left panel: a ¼ 4 July, b ¼ 11 September, c ¼ Halloween, d ¼ Christmas day, e ¼ New Year’s Eve and
New Year’s day, f ¼ Valentine’s day, g ¼ April Fool’s day) and around a close friend’s birthday as
zero (lower right panel)
Copyright # 2010 John Wiley & Sons, Ltd.
Appl. Cognit. Psychol. (2010)
DOI: 10.1002/acp
Self-reference effect for dates
To investigate whether other salient events cause a similar clustering of dates, all recalled
birthdays were recoded as the number of days from the date of test (as day zero). Figure 2
(upper right panel) shows that there is some clustering using this method (with the most
remembered birthdays falling on the day before the test session), but this is a less
pronounced peak than using participants’ own birthdays (test date distribution SD ¼ 13.19;
z ¼ 6.49). In addition, we were interested in the possible effects of salient public events and
national holidays on retrieval. Thus, all the dates were recoded around Christmas day as an
arbitrary zero point (lower left panel) to investigate whether any salient calendar event
causes clustering. Distribution peaks occur on public holidays and dates of memorable
events (e.g. September the 11th), suggesting that salient dates are used to organise and
retrieve birthdays. The seven public events associated with heightened retrieval are labelled
on Figure 2. The z-scores related to each public event are: 4 July (z ¼ 2.85), 11 September
(z ¼ 4.35), Halloween (z ¼ 4.42), Christmas day (z ¼ 4.56), New Year’s Eve (z ¼ 3.33),
New Year’s day (z ¼ 4.63), Valentine’s day (z ¼ 5.52), and April Fool’s day (z ¼ 4.49). We
suggest that self cues are most powerful; participants are three times more likely to recall a
friend’s birthday if it falls on their own birthday than if it falls on Christmas day, for
example.
As most SRE studies employ an ‘other’ condition (e.g. Symons & Johnson, 1997) to
compare with self-referent retrieval, we included a similar analysis in the present study. To
generate an ‘other’ condition, we used a birthday of someone the participant generated. We
reasoned that the first birthday generated might be a salient other, and we were able to
establish this by using the closeness ratings generated for each friend. Thus, each
participant’s first-recalled friend (only using cases where this friend was ranked as being
‘very close’ to the participant) was used as a further clustering date. This produced a
sample of 1729 dates (mean count of birthdays ¼ 39.03; SD ¼ 7.29). These birthdates were
then used as day zero, with all following birthdays given by each participant recoded as the
number of days before or after this date. Results (shown in Figure 2, lower right panel),
demonstrate that the birthday of a close friend (e.g. close ’other’) has some effect on
enhancing retrieval (z ¼ 7.12), but not to the extent that the self does.
CONCLUSIONS
The present study shows that birthdays are best recalled if they are close to the date of one’s
own birthday. The method for collecting these birthday dates was very simple, and,
crucially, involved no explicit reference to the self. In this respect this paper presents a pure
demonstration of the powerful effect of the self in retrieval. The effect of the self produces a
more clustered distribution of recalled dates than when other standard comparison points
are used (e.g. a close ‘other’, date of test, and salient public events such as Christmas,
11 September and Halloween).
These findings support theories of the reminiscence bump that relate the heightened
retrieval of events from young adulthood to the importance of this time for identityformation (e.g. Conway & Haque, 1999). This study demonstrates a SRE in long-term
memory organisation, and supports the view that the self plays a central role in memory
encoding and retrieval (e.g. Conway, 2005). Results also suggest that the self acts as a
uniquely elaborate construct, as it exerts a more powerful effect on recall than a close other
or salient calendar events. A common critique of the SRE is that it does not necessarily
indicate the uniqueness of self-referential processing (e.g. Symons & Johnson, 1997). This
Copyright # 2010 John Wiley & Sons, Ltd.
Appl. Cognit. Psychol. (2010)
DOI: 10.1002/acp
C. J. Rathbone and C. J. A. Moulin
proposal is supported by evidence that encoding with reference to other highly elaborate
and organised structures enhances retrieval to a similar extent (e.g. Gillihan & Farah, 2005;
Klein & Kihlstrom, 1986). The present study uses a different approach, by examining the
implicit retrieval of self-referenced information. As there are no explicit self-encoding
versus other-encoding conditions (and participants were unaware that they would be asked
for their own birthday), we suggest that this task reflects free recall of un-primed
information. Results indicate that the self organises retrieval in a more pronounced way
than a close other or salient calendar events. Thus, although this study does not employ a
standard SRE paradigm, results suggest that there is a unique effect of the self in retrieval.
If birthdays are semantic facts we store about others, then this study has clearly shown
that such material is organised and retrieved in relation to self-relevant information. In
conclusion, these novel findings are taken as further evidence that the self has a strong
influence over memory organisation. Information is temporally organised around a time
important to the self, even when—as in this study—the task is not explicitly about selfreference.
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