Itsy bitsy spider?: Valence and self-relevance predict size estimation

- Spider-fearful individuals rated spiders as larger than controls.
- Only the spider-fearful individuals rated spiders as larger than butterflies.
- Spider-fearful individuals did not show bias in the size estimation of wasps.
- Bias in size estimation was specific to self-relevant stimuli.
- Aversive stimuli did not induce size bias when irrelevant to an individual

The current study explored the role of valence and self-relevance in size estimation of neutral and aversive animals. In Experiment 1, participants who were highly fearful of spiders and participants with low fear of spiders rated the size and unpleasantness of spiders and other neutral animals (birds and butterflies). We found that although individuals with both high and low fear of spiders rated spiders as highly unpleasant, only the highly fearful participants rated spiders as larger than butterflies. Experiment 2 included additional pictures of wasps (not self-relevant, but unpleasant) and beetles. The results of this experiment replicated those of Experiment 1 and showed a similar bias in size estimation for beetles, but not for wasps. Mediation analysis revealed that in the high-fear group both relevance and valence influenced perceived size, whereas in the low-fear group only valence affected perceived size. These findings suggest that the effect of highly relevant stimuli on size perception is both direct and mediated by valence.