Attention Towards Pupil Size in Humans and Bonobos (Pan paniscus)

Area of Science:

• Cognitive Psychology
• Comparative Psychology
• Primatology

Background:

• Humans exhibit an attentional bias towards emotional signals.
• Implicit emotional cues, like pupil size, convey social information and influence judgment.
• It remains unclear if attentional biases extend to subtle, implicit emotional cues like pupil dilation.

Purpose of the Study:

• To investigate attentional bias towards varying pupil sizes in humans and bonobos.
• To determine if subtle, implicit emotional signals (pupil size) capture attention similarly to overt emotional expressions.

Main Methods:

• Employed a dot-probe task with 150 human participants and 4 bonobos.
• Utilized linear mixed multilevel models to analyze reaction times.
• Presented stimuli via online interface for humans and touchscreen for bonobos.

Main Results:

• Humans demonstrated a significant attentional bias favoring dilated pupils over intermediate and small pupils.
• No significant attentional bias related to pupil size was observed in bonobos.
• Results suggest humans attend to pupil size as a subtle emotional cue.

Conclusions:

• Human attention is biased towards dilated pupils, extending known attentional biases to implicit emotional signals.
• Methodological differences necessitate caution when interpreting results for bonobos.
• Further research is required to confirm or refute attentional biases towards pupil size in bonobos.