Download avoidance behavior

Avoiding Bad Things
Instrumental Conditioning Procedures
• Review of Instrumental Contingency Figure
– Punishment : behavior followed by an aversive
• decreases the behavior
• Picking up a hot object hurts so do not touch it in the future
– Negative reinforcement : behavior to prevent an aversive
• increases the behavior
• Using a glove to pick up a hot object avoids getting hurt so use the glove in the future
• Called avoidance behavior
• Avoidance behavior
– avoidance : when the behavior results in avoiding the aversive stimulus
– However, escape: when behavior is in response to the aversive stimulus
• Picking up a hot object hurts so quickly drop it
• Similarity between punishment and avoidance:
– behavior serves to minimize contact with the aversive stimulus
– in avoidance, taking a specific action prevents the aversive stimulus
• Called active avoidance
– in punishment, refraining from action minimizes contact with the aversive
stimulus
• Called passive avoidance
Origins of the Study of Avoidance Behavior
• First experiments conducted by Bechterev (1913)
• Based on Pavlov’s classical conditioning using an aversive US
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Participants instructed to place a finger on a metal plate
A warning stimulus (CS) was then presented, followed by a brief shock (US)
So this is fear conditioning
The participants quickly lifted their finger off the plate after being shocked,
which is escape behavior
– After a few trials, they also learned to make the response during the CS,
which is avoidance behavior
• This is instrumental (negative reinforcement) conditioning
• escape-avoidance figure
• Originally this experiment was viewed as a standard example of
Pavlovian conditioning
Origins of the Study of Avoidance Behavior
• Brogden, Lipman, & Culler (1938)
– compared standard classical conditioning procedure and instrumental
avoidance
– Tested 2 groups of guinea pigs in a rotating wheel
– A tone served as the CS and a shock as the US
– The shock stimulated the animals to run and rotate the wheel
– For the classical conditioning group, the shock was presented 2 s after the
onset of the tone
– For the avoidance conditioning group, the shock also followed the tone when
the animals did not make the CR (a small movement of the wheel)
– if the avoidance animals moved the wheel during the tone CS before the
shock occurred, the scheduled shock was omitted
– Figure 10.1
FIGURE 10.1
Panel A: Moder n running wheel for rodents. Panel B: Percentage of trials when guinea pigs moved the
running wheel on successive days of training. Such responses prevented shock delivery for the
avoidance group but not for the classical group. (From “The Role of Incentive in Conditioning and
Extinction” by W. J. Brogden, E. A. Lipman, and E. Culler, 1938. American Journal of Psychology, 51,
pp. 109–117.)
The Principles of Learning and Behavior, 7e by Michael Domjan
Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
The Discriminated Avoidance Procedure
• A warning stimulus (e.g., a light) signals a forthcoming shock.
• If the required response is made during the light (warning
stimulus), before the shock occurs, the subject avoids the shock.
• If a response is not made during the warning stimulus of the light,
the shock occurs, and terminates when the required response is
made (i.e., escape).
• Figure 10.2
The Principles of Learning and Behavior, 7e by Michael Domjan
Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
The Discriminated Avoidance Procedure
• Discriminated avoidance procedures are often conducted in a shuttle
box
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Figure 10.3
the shuttle box consists of 2 compartments separated by a barrier
the animal is placed on one side of the apparatus at the start of the trial
When a CS is presented
• cross the barrier before a set time interval then no shock is presented (avoidance)
• do not cross the barrier before end of interval then shock is given (escape)
– the next trial can be started with the animal in the second compartment
shuttle avoidance
• two-way shuttle avoidance vs one-way shuttle avoidance:
– one-way avoidance is always from the same side and is easier to learn
– two-way requires avoiding signal from either side
The Principles of Learning and Behavior, 7e by Michael Domjan
Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
The Two-Process Theory of Avoidance
• Avoidance responses are made to avoid the aversive stimulus
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involve a negative contingency between a response and an aversive stimulus
Make response to not get the aversive
Why is this avoidance behavior maintained?
Avoiding the aversive should result in extinction
• Can the absence of an aversive provide reinforcement?
• The Two-Process Theory (see table 7.1)
– Explains avoidance learning in terms of two necessary processes:
– first, the subject learns to associate the warning stimulus with the shock
which is a classical conditioning process
• CS (light) --> US (shock) ---> UR (fear)
• this will always happen at the beginning of the training
– the second, operant conditioning process, the subject can be negatively
reinforced
• crossing barrier removes CS fear stimulus
• which strengthens the response
• learn to escape from the CS and the fear that it elicits.
Experimental Analysis of Avoidance Behavior
• Experimental procedures used to test the Two-Process Theory
• Escape From Fear Experiments
• In the typical avoidance procedure, classical conditioning of fear
and instrumental reinforcement through fear reduction occur
intermixed in a series of trial
• If Two-Process theory is right, then separating the two processes
should still lead to successful learning.
• Two phases :
– First, classical conditioning to acquire fear of CS
– Second, escape training with CS as Aversive stimulus
• (US no longer presented)
– will the subject learn a response to escape from just the CS
Experimental Analysis of Avoidance Behavior
• Escape From Fear Experiments
• Esmoris-Arranz (2003)
– Fear Conditioning:
• In one side of the box with no escape possible
• 15 sec CS audiovisual + 15 sec US shock
– simultaneous CS/US
– delayed CS then US
– Control group with unpaired CS and US
– Escape Testing: placed in shuttle box with access to other side
• Evidence of learning in both the delayed and simultaneous groups but not in the
unpaired group
• Figure 10.4
FIGURE 10.4
Mean latencies to escape from a CS that was either conditioned using a delayed conditioning procedure,
a simultaneous conditioning procedure, or was presented unpaired with the US (based on EsmorísArranz, Pardo-Vázquez, & Vázquez-Garciá, 2003).
The Principles of Learning and Behavior, 7e by Michael Domjan
Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.
Independent Measurement of Fear During Acquisition of
Avoidance Behavior
• If fear motivates and reinforces avoidance responding, then the
conditioning of fear and the conditioning of instrumental avoidance
behavior should be highly correlated
• However, the level of fear is not always positively correlated with
avoidance
• Animals often become less fearful as they become more proficient
in performing the avoidance response
• Warning signal in an avoidance procedure comes to elicit fear
– presentation of that stimulus in a conditioned suppression procedure should
result in suppression of behavior
– Gradual reduction in fear of the warning signal even though avoidance
behavior continues
Independent Measurement of Fear During Acquisition of Avoidance
Behavior
• Lovibond (2008) using college students with Fear conditioning under
three different conditions
– (A) CS (red) - US (shock) with the opportunity to avoid the US
– (B) CS (blue) - US (shock) with no opportunity to avoid the US
– (C) CS (green) only - never US
• recorded skin conduction as a measure of fear
– Decreased across trials for red opportunity to avoid
– Increased across trials for blue no opportunity to avoid
– Low for green no shock
• ratings of expectation of US
– Decreased across trials for red opportunity to avoid
– Increased across trials for blue no opportunity to avoid
– Decreased across trials for green no shock
• Figure 10.5
FIGURE 10.5
Changes in skin conductance and expectancy of shock across trials for a warning stimulus in an
avoidance procedure (A+), a Pavlovian CS paired with shock (B+), and a stimulus never paired with
shock (C−) (based on Lovibond et al., 2008).
The Principles of Learning and Behavior, 7e by Michael Domjan
Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.