The current study utilized two experiments to assess Smith's (1981) simple per capita-maximization model, which provides a quantitative framework for predicting optimal group sizes in social foraging contexts. Participants engaged in a social foraging task where they chose to forage for points exchangeable for lottery prizes either alone or in a group that has agreed to pool and share all resources equally. In Experiment 1, groups (“settlements”) of 10 or 12 participants made repeated group membership choices. Settlements were exposed to three conditions in which the optimal group size was either 2, 5, or 2 for the 10 person settlement or 3, 4, or 6 for the 12 person settlement. A linear regression of the data from Experiment 1 revealed a strong relationship between the observed group sizes and group sizes predicted by the simple per capita maximization model. Experiment 2 was a systematic replication of Experiment 1 in which single participants foraged for shared resources with groups of automated players in a computerized simulation. Automated player group choices mirrored group choices of participants in Experiment 1; excluding the data for the best performing participant. Thus, the participant acted essentially in the stead of the best performing participant for each condition. Two logistic regressions provided mixed support for the model, while failing to replicate the results of Experiment 1, providing mixed support for the use of the simple per capita maximization model in predicting group sizes in social foraging contexts.