Interpreting and responding to ambiguous natural images in spider phobia

Abstract

Background and objectivesThe fast detection of and response to threatening stimuli is an important task of the human visual and motor systems, and is especially challenging when stimuli are ambiguous. This study investigates the perception, evaluation and fast response to ambiguous natural spider stimuli in spider-fearful and non-anxious participants. MethodsStimuli were created by gradually morphing natural images of spiders and non-spiders (a crab, a starfish, a bunch of keys, and a flower). In Study 1, participants rated the images on perceptual and emotional dimensions and responded to them in a response priming task to measure rapid information processing. In Study 2, results were validated and extended in a different paradigm by using a go/no-go task. ResultsAs expected, spider-fearful participants showed an interpretative bias for ambiguous stimuli (i.e., perceived them as more similar to spiders) and rated spider(-like) stimuli as more unpleasant, arousing, and disgusting. In Study 1, spider stimuli were preferentially processed in spider-fearful participants as observed in faster responses to spider targets–however, responses were not different to comparison participants for ambiguous stimuli. Study 2 suggests that this finding can be explained by differences in stimulus duration. LimitationsNo participants with positive attitudes towards spiders or a second fearful comparison group were included. ConclusionsWe suggest that these findings can be explained by the nature of the applied tasks that tap into early phases of visual processing, thereby relying on feedforward-mediated low-spatial-frequency information extracted via the fast, subcortical path to the amygdala.