Itsy Bitsy Spider…: Infants React with Increased Arousal to Spiders and Snakes

Area of Science:

• Evolutionary psychology
• Developmental psychology
• Neuroscience

Background:

• Attention biases towards ancestral threats (spiders, snakes) are documented across age groups.
• Physiological arousal responses to these threats in infants remain largely unexplored.

Purpose of the Study:

• To investigate whether ancestral threat stimuli (spiders, snakes) elicit physiological arousal in 6-month-old infants.
• To examine pupillary responses as an indicator of noradrenergic system activation in infants exposed to threat-related and neutral stimuli.

Main Methods:

• Infants were presented with images of spiders versus flowers, and snakes versus fish.
• Pupillary responses, reflecting noradrenergic system activity, were measured.
• Study designs included within-subjects and between-subjects comparisons.

Main Results:

• Infants exhibited significantly increased pupillary dilation when viewing spiders and snakes compared to flowers and fish.
• This pupillary response indicates heightened physiological arousal in infants towards ancestral threat stimuli.
• Results were consistent across different study designs.

Conclusions:

• The findings support the hypothesis of an evolved preparedness for fear in infants.
• Infants demonstrate early-stage arousal responses to evolutionarily relevant threats.
• This research provides insights into the developmental origins of fear.