The purpose of this study was to determine whether children can learn to cooperate in what has been described as the "minimal social situation." The research also compared the effectiveness of verbal instructions and a training task for teaching subjects the "win-stay, lose-change" rule. This rule has been used to explain the development of cooperation in the minimal social situation. Subjects were 19 teams of first-, second-, and third-graders. Five teams were composed of two girls; six were girl-boy teams; and eight were boy-boy teams. Ten of the 19 teams learned to cooperate in the minimal social situation without treatment. Two of four teams given the rule training procedure learned to cooperate after having failed to learn under typical minimal social conditions. Of five teams given verbal instructions, four learned to cooperate immediately. The probability of following the win-stay, lose-change rule was approximately 50% initially and did not increase significantly in later sessions. It is not clear then that following this rule is a prerequisite for the development of a cooperative exchange. Explanations in the literature which suggest subjects learn a single rule, i.e., win-stay, lose-change, may be misleading since children evidenced a variety of rules, any of which might have been reinforced or punished over the course of the experiment.

Like other animals, humans explore to learn about the world, and exploit what we have learned in order to maximize reward. The trade-off between exploration and exploitation is a widely-studied topic that cuts across multiple domains, including animal ecology, economics, and computer science. This work approaches the explore-exploit dilemma from the perspective of cognitive neuroscience. In particular, how are our decisions to explore or exploit represented computationally? And how is that representation implemented in the brain? Experiment 1 examined neural signals following outcomes in a risk-taking task. Explorations – defined as slower responses – were preceded by an enhancement of the P300, a component of the human event-related brain potential thought to reflect a phasic release of norepinephrine from locus coeruleus. Experiment 2 revealed that the same neural signal precedes feedback in a learning task called a two-armed bandit. There, a reinforcement learning model was used to classify responses as either exploitations or explorations; exploitations were driven by previous rewards, and explorations were not. Experiments 3 and 4 extended these results in three important ways. First, evidence is presented that the neural signal observed in Experiments 1 and 2 was driven not only by the upcoming decision, but also by the preceding decision (perhaps even more so). Second, Experiments 3 and 4 involved increasingly larger action spaces. Experiment 3 involved choosing from among either 4, 9, or 16 options. Experiment 4 involved searching for rewards in continuous two-dimensional map. In both experiments, the feedback-locked P300 was enhanced following exploration. Third, exploitation was the more common strategy in Experiments 1 and 2. Thus, it was unclear whether the exploration-related P300 enhancement observed there was due to exploration per se, to exploration rate, or to the fact that exploration was rare compared to exploitation. Experiment 3 partially address this by eliciting different rates of exploration; the exploration-related P300 effect correlated with rate of exploration. In Experiment 4, exploration was more common than exploitation (in contrast to Experiments 1–3); even so, exploration was followed by a P300 enhancement. Together, Experiments 1–4 suggest the presence of a general neural system related to exploration that operates across multiple task types (discrete to continuous), regardless of whether exploration or exploitation is the more common task strategy. The proposed purpose of this neural signal is to interrupt one mode of decision-making (exploration) in favour of another (exploitation). / Graduate