# Ensemble size perception as a case study of the bounds of adaptation

## TL;DR

This study investigates whether people adapt to different aspects of visual size perception, finding that adaptation occurs for cumulative size but not average size.

## Contribution

The study challenges the assumption that adaptation occurs for all perceptually encoded properties by showing no adaptation to average size.

## Key findings

- Robust adaptation occurs for cumulative size of dot arrays.
- No adaptation is observed for average size of dot arrays.
- Adaptation effects remain even when controlling for brightness confounds.

## Abstract

Repulsive adaptation effects are widely assumed to obtain for all perceptually represented dimensions. However, the ubiquity of adaptation effects within perception remains untested. We examined ensemble size adaptation as a case study to probe whether adaptation occurs for all perceptually encoded properties. Across four experiments, we investigated whether observers adapt to average size and/or cumulative size of dot arrays. In Experiments 1a, 1b, and 1c participants adapted to displays varying in cumulative and/or average dot size, then judged either the average dot size (1a) or the cumulative dot size (1b) of paired test displays. Results revealed robust adaptation to cumulative size but not average size, regardless of task instructions, and even when confounds with brightness were controlled for (1c). Experiment 2 tested “reverse” adaptation to displays containing smaller average and/or cumulative dots size and, again, found adaptation effects for cumulative size only. The observed lack of adaptation to average size across each of these experiments forces a reinterpretation of previous studies that have investigated size adaptation and calls into question arguments which have assumed adaptation to be universal within perception, given a large body of work that finds average size to be perceptually encoded.