Effectiveness of the monkey model and of the two human models (‘stimulus-enhancing’ vs. ‘monkey-like’).

<p>A positive learning Δ denotes fewer errors for ‘social’ pairs than for the ‘individual’ pairs tested during the very same sessions, i.e. a beneficial model. A negative learning Δ denotes more errors for ‘social’ than for ‘individual’ pairs, i.e. a detrimental model. Results are illustrated for each monkey and for the group. Monkeys are grouped per trio of housemates according to their rank in the group hierarchy. For the detrimental ‘stimulus-enhancing’ model, two bars were truncated to keep the figure balanced. The actual scores were −103 for the top-ranking male (♂ 1) and −63 for the bottom-ranking female (♀ 3). Note that although 5/6 monkeys benefited slightly more from the monkey than from the ‘monkey-like’ human, the reverse pattern did occur too (♂ 2), hence, the indistinguishable group means yielded by the two beneficial models.