Adaptation to numerosity affects the pupillary light response
View abstract on PubMed
Summary
This summary is machine-generated.Pupillary light responses are smaller when fewer items are perceived, even if stimuli are identical. This demonstrates numerosity adaptation influences unconscious behaviors.
Area Of Science
- Visual perception
- Neuroscience
- Psychophysics
Background
- The pupillary light response (PLR) is an automatic reflex that regulates light entering the eye.
- Previous research indicated PLR gain is influenced by visual numerosity, with fewer items eliciting weaker responses.
- The role of perceptual adaptation in modulating this automatic response remained unclear.
Purpose Of The Study
- To investigate whether numerosity adaptation affects the pupillary light response.
- To determine if perceived numerosity, rather than actual item count, drives PLR modulation.
- To explore numerosity as a fundamental visual feature influencing subconscious behaviors.
Main Methods
- Twenty-eight participants underwent numerosity adaptation to either low (10 dots) or high (160 dots) stimulus sets.
- Following adaptation, participants viewed dot arrays (10-40 dots) with constant luminance and either variable or homogeneous dot sizes.
- Pupil size was measured during passive viewing, and adaptation effects were verified psychophysically.
Main Results
- Adaptation to high numerosity led to a systematic decrease in perceived numerosity compared to low numerosity adaptation.
- Pupillary light responses were significantly smaller after adaptation to high numerosity stimuli.
- This effect persisted regardless of dot size variability, indicating a robust influence of perceived numerosity.
Conclusions
- Perceptual adaptation to numerosity influences the pupillary light response, demonstrating its automatic nature.
- Numerosity is a primary visual attribute spontaneously processed, affecting even task-irrelevant, unconscious behaviors.
- The findings support the view that the visual system actively estimates and encodes numerosity, impacting physiological responses.

