A 150-millisecond glance at matching facial emotions tells people if a crowd is a group

In two studies using about 200 Instagram group photos, people judged how unified a group was after just 150 milliseconds, and those snap judgments, driven by how similar faces' emotions were, closely matched judgments made after 3 seconds.

An observer glances at two crowds, one with matching joyful faces that looks unified and one with mixed emotions that looks scattered.
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People can tell whether a gathering of strangers looks like a real, unified group in a fraction of a second, and they do it largely by noticing whether everyone’s faces show the same emotion. A pair of experiments found that judgments made after a 150-millisecond glance closely matched those made after looking for 3 seconds.

The research, by Sarah Ariel Lamer of the University of Tennessee, Knoxville, with Spencer Dobbs of Southeastern Louisiana University and Lindsay Goolsby, Timothy D. Sweeny and Max Weisbuch of the University of Denver, was published online on February 10, 2026, in the Journal of Experimental Social Psychology. Its title is “Ensemble perception in entitativity judgments of natural crowds”.

Real groups from Instagram

Psychologists use the word entitativity for how much a collection of people seems like a single, coherent unit. The team tested whether this impression rests on ensemble coding, the visual system’s ability to extract an average or spread from many faces at once.

Instead of staged lab photos, the researchers used a representative sample of about 200 natural group images collected from Instagram. Every person in every image was independently coded for facial expression, gender and race, and participants rated how much emotions varied within each group.

In the first study, participants viewed each image for 5 seconds and rated either how much emotion the members shared or how entitative the group seemed. The second study varied viewing time between 150 milliseconds, 750 milliseconds and 3 seconds, and showed some participants versions with faces hidden.

First impressions do the work

All of the researchers’ hypotheses were supported. People perceived how variable a group’s emotions were after the briefest exposure, and those rapid perceptions predicted entitativity judgments made with longer viewing. Entitativity judgments made after 150 milliseconds approximated those made after 3 seconds.

The effects were largely independent of the race and gender makeup of the groups. The authors conclude that complex conceptual judgments about small groups can be formed in the first instants of perception.

Study Details:

  • Title: Ensemble perception in entitativity judgments of natural crowds
  • Authors: Sarah Ariel Lamer, Spencer Dobbs, Lindsay Goolsby, Timothy D. Sweeny, Max Weisbuch
  • Journal: Journal of Experimental Social Psychology
  • Publication Date: February 10, 2026
  • DOI: 10.1016/j.jesp.2026.104889