Build-up of serial dependence in color working memory

Joao Barbosa,Albert Compte

doi:10.1038/s41598-020-67861-2

Joao Barbosa, Albert Compte

Open Access

https://doi.org/10.1038/s41598-020-67861-2

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Abstract

Serial dependence, how immediately preceding experiences bias our current estimations, has been described experimentally during delayed-estimation of many different visual features, with subjects tending to make estimates biased towards previous ones. It has been proposed that these attractive biases help perception stabilization in the face of correlated natural scene statistics, although this remains mostly theoretical. Color, which is strongly correlated in natural scenes, has never been studied with regard to its serial dependencies. Here, we found significant serial dependence in 7 out of 8 datasets with behavioral data of humans (total n = 760) performing delayed-estimation of color with uncorrelated sequential stimuli. Moreover, serial dependence strength built up through the experimental session, suggesting metaplastic mechanisms operating at a slower time scale than previously proposed (e.g. short-term synaptic facilitation). Because, in contrast with natural scenes, stimuli were temporally uncorrelated, this build-up casts doubt on serial dependencies being an ongoing adaptation to the stable statistics of the environment.

Highlights

Serial dependence, how immediately preceding experiences bias our current estimations, has been described experimentally during delayed-estimation of many different visual features, with subjects tending to make estimates biased towards previous ones
By controlling for the known systematic biases in color perception we characterize for the first time, contrary to our hypothesis, a slower dynamics of increasing serial dependence through the experimental session, despite uncorrelated stimulus statistics
Serial bias build-up was not correlated with the subjects’ squared error trend during the session (Supplementary Fig. S3). These control analyses show that serial bias build-up during experimental sessions was not associated with trends in performance dynamics as a result of subjects getting familiar with the task or tiredness. These results show that serial dependence is not stable on the time scale of one experimental session, as previously assumed, and it discards a mechanism that adapts to stimulus statistics

Summary

Introduction

How immediately preceding experiences bias our current estimations, has been described experimentally during delayed-estimation of many different visual features, with subjects tending to make estimates biased towards previous ones. Similar to other perceptual biases for other visual features[34,35], these systematic color biases adapt to stimulus statistics in the course of one e xperiment[33] This suggests that typical perceptual bias adaptations occur in time scales of minutes to hours. If serial biases are subject to adaptation with a similar time scale, when exposed to long sessions with uncorrelated stimulus statistics they should decrease or, in case of not being adaptive, they should remain stable. By controlling for the known systematic biases in color perception we characterize for the first time, contrary to our hypothesis, a slower dynamics of increasing serial dependence through the experimental session, despite uncorrelated stimulus statistics

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