Internal domain generality for ensemble perception of average orientation: Comparing and integrating information from multiple stimulus categories.

Ensemble perception (the extraction of summary statistics from groups of objects) operates across a range of visual features and stimuli. Ensemble displays usually contain identical stimuli, although natural environments are composed of more heterogeneous items, raising the question of whether ensemble mechanisms can generalize across stimulus types ("internal domain generality"). We examined whether ensemble perception for orientation operates similarly across displays composed of different stimulus types (faces, shoes, triangles). In Experiment 1, participants compared average orientations across two homogeneous ensembles that were made up of either the same or different stimulus types. Participants were equally accurate when the stimulus types were the same compared to when they were different, suggesting that ensemble abilities are governed by a domain-general mechanism. In Experiments 2A and 2B, participants were shown one ensemble that was made of one stimulus type (pure) or two (mixed) and determined whether the direction of a probe arrow matched the average orientation. There were minimal differences in the pure condition. In the mixed condition, stimulus specificities emerged. When the ensemble contained triangles, participant responses were biased in the direction of those triangles. Further evidence of this triangle bias was found via a continuous report task (Experiment 3). When every item within an ensemble is the same, ability to extract summary statistics is similar across ensembles, but having more than one stimulus type within a single ensemble interferes with the extraction and subsequent report, suggesting that ensemble perception abilities show internal domain generality, but specificities emerge under certain circumstances. (PsycInfo Database Record (c) 2026 APA, all rights reserved).