A General Ability for Simple and Complex Ensemble Judgments

People can report summary statistics for various features about a group of objects. One theory is that different abilities support ensemble judgments about low-level features like color vs. high-level features like identity. Existing research mostly evaluates such claims based on evidence of correlations within and between feature domains. However, correlations between two identical tasks that only differ in the type of feature for ensemble judgments can be inflated by method variance. Another concern is that conclusions about high-level features are mostly based on faces. We used latent variable methods on data from 237 participants to investigate the abilities supporting low-level and high-level feature ensemble judgments. Ensemble judgment was measured with six distinct tests, each requiring judgments for a distinct low-level (orientation, lightness, aspect ratio) or high-level feature (bird species, Ziggerin identity, Transformer identity), using different task requirements in each task (mean estimation, mean matching, diversity comparison). We also controlled for other general visual abilities when examining how low-level and high-level ensemble abilities relate to each other. Confirmatory factor analyses showed a perfect correlation between the two factors, suggesting a single ability. A nested model comparison confirmed that using one ensemble perception (EP) factor rather than two did not impair model fit. There was a strong unique relationship (.9) between these two factors, beyond the influence of object recognition and perceptual speed. Additional results from 117 of the same participants also ruled out an important role for working memory in explaining the EP factor. Our results demonstrate that the ability common to a variety of ensemble judgments with low-level features is the same as that common to a variety of ensemble judgments with high-level features.