The following is a summary of “Perceptual history biases in serial ensemble representation,” published in the March 2023 issue of Ophthalmology by Khayat, et al.

Ensemble perception is the visual system’s ability to represent similar objects as a unified percept using summary statistical information. Previous studies have mainly focused on current trial averages, with little attention given to the effect of prior experiences. However, recent studies have found that mean ensemble estimations tend to contract toward previously presented stimuli. It was essential to consider the temporal aspect of ensemble statistics because in real dynamic environments, humans encounter objects over time. Statistical information is learned implicitly, shaping perception and promoting environmental stability. For a study, researchers sought to investigate whether prior information beyond the current trial influences implicit perceptual decisions. 

The experiment involved serially presenting six circles of varying sizes and asking participants to choose which was present in the sequence. The two test items were sometimes equidistant from the current trial meaning isolating the influence of earlier trials. 

The results indicated that judgments were biased towards the current trial mean when informative, but on equidistant trials, judgments were biased towards previously experienced stimuli. 

It was concluded that ensemble perception was influenced not only by the current trial mean but also using recently seen ensembles, and these influences were somewhat correlated among participants.