biostudies-literatureBradley BSBritish AcademyCharles Sturt University385https://www.ebi.ac.uk/biostudies/studies/S-EPMC5352679biostudies-literatureUnknown8Infant sociability is generally conceived in terms of dyadic capacities and behaviors. Recently, quantitative evidence has been published to support arguments that infants achieve a criterion for groupness: the capacity to interact simultaneously with two others. Such studies equate this capacity with alternating dyadic acts to the two other members of an interacting trio. Here we propose a stricter threefold criterion for infant groupness, of which the crux is whether the social behavior of an infant at time B is shown to be influenced by what two or more group-members were previously doing at time A. We test the viability of this conceptualization: (a) through its justification of the novel laboratory procedure of studying infant sociability in infant-peer quartets (rather than trios); aFrontiers in psychologyGroupness in Preverbal Infants: Proof of Concept.PMC5352679A541-104-202952008-97469Smithson MBradley BSfalseGroupness in Preverbal Infants: Proof of Concept.Infant sociability is generally conceived in terms of dyadic capacities and behaviors. Recently, quantitative evidence has been published to support arguments that infants achieve a criterion for groupness: the capacity to interact simultaneously with two others. Such studies equate this capacity with alternating dyadic acts to the two other members of an interacting trio. Here we propose a stricter threefold criterion for infant groupness, of which the crux is whether the social behavior of an infant at time B is shown to be influenced by what two or more group-members were previously doing at time A. We test the viability of this conceptualization: (a) through its justification of the novel laboratory procedure of studying infant sociability in infant-peer quartets (rather than trios); a2017-01-01T00:00:00Z20172025-04-26T18:54:46.942Z2019-03-27T02:38:44ZS-EPMC53526792836087610.3389/fpsyg.2017.00385