UCS expectancy biases and specific phobias.
There is now considerable evidence that phobic responding is associated with a bias
towards expecting aversive or traumatic outcomes following encounters with the
phobic stimulus (e.g. Davey, 1995). In terms of conditioning contingencies, this can
be described as a bias towards expecting an aversive or traumatic outcome (the
unconditioned stimulus - UCS) following a phobic stimulus (the conditioned
stimulus - CS).
Research into the role of UCS expectancy biases in the development and
maintenance of specific phobias has three basic requirements. First, it is not clear
whether the ues expectancy biases evidenced in specific phobias represent a
stimulus specific response or a more generalised associative phenomenon. Second, it
is not clear what dispositional or state factors might contribute to the development
and maintenance of such ues expectancy biases. Third, it is not clear what type of
cognitive mechanisms might underlie UCS expectancy biases. This thesis uses a
thought experiment version of a threat conditioning procedure to explore these
The key findings indicate that spider phobics tend to overestimate the likelihood of
aversive outcomes following phobic, but not other fear relevant stimuli, and tend to
underestimate the likelihood of aversive outcomes following fear irrelevant stimuli in
comparison to non-phobic controls. This dichotomous ues expectancy bias is
mirrored both in the evaluation of stimuli in terms of dangerousness and valance, and
in the generation of harm and safety cues with regards to these stimuli. Both positive
and negative mood states, but not arousal states contributed to ues expectancy
inflation, and in the case of revulsive animals induced state disgust also increased
reported ues expectancies.
The thesis concludes with an evaluation of the role of UCS'S expectancies in the
development and maintenance of specific phobias, and a discussion of the
implications of these findings for our understanding of the information processing
mechanisms underlying the specific phobias.