We explored whether rhesus monkeys (Macaca mulatta) share one important feature of human essentialist reasoning: the capacity to track category membership across radical featural transformations. Specifically, we examined whether monkeys--like children (Keil, 1989)--expect a transformed object to have the internal properties of its original…

It is currently being debated whether human newborns' preference for faces is due to an unlearned, domain-specific and configural representation of the appearance of a face, or to general mechanisms, such as an up-down bias (favouring top-heavy stimuli, which have more elements in their upper part). Here we show that 2-day-old domestic chicks,…

We report here that monkeys can actively match the number of sounds they hear to the number of shapes they see and present the first evidence that monkeys sum over sounds and sights. In Experiment 1, two monkeys were trained to choose a simultaneous array of 1-9 squares that numerically matched a sample sequence of shapes or sounds. Monkeys…

Eight crows were taught to discriminate overlapping pairs of visual stimuli (A+ B-, B+ C-, C+ D-, and D+ E-). For 4 birds, the stimuli were colored cards with a circle of the same color on the reverse side whose diameter decreased from A to E (ordered feedback group). These circles were made available for comparison to potentially help the crows…