When we compare human gestures to those of other apes, it looks at first like there is nothing much to compare at all. In adult humans, gestures are thought to be a window into the thought processes accompanying language, and sign languages are equal to spoken language with all of its features. Some research firmly emphasises the differences between human gestures and those of other apes; however, the question about whether there are any commonalities is rarely investigated, and has mostly been confined to pointing gestures. The gestural repertoires of nonhuman ape species have been carefully studied and described with regard to their form and function-but similar approaches are much rarer in the study of human gestures. This paper applies the methodology commonly used in the study of nonhuman ape gestures to the gestural communication of human children in their second year of life. We recorded (n = 13) children's gestures in a natural setting with peers and caregivers in Germany and Uganda. Children employed 52 distinct gestures, 46 (89%) of which are present in the chimpanzee repertoire. Like chimpanzees, they used them both singly, and in sequences, and employed individual gestures flexibly towards different goals.

The main aim of this paper is to highlight the need to address the conceptual problem of ‘implicit knowledge’ or ‘implicit cognition’ — a notion especially important in the study of the nonverbal minds of animals and infants. We review some uses of the term ‘implicit’ in psychology and allied disciplines, and conclude that conceptual clarification of this notion is not only lacking, but largely avoided and reduced to a methodological problem. We propose that this elusive notion is central in the study not only of animal and infant minds, but also the human adult mind. Some promising approaches in developmental and evolutionary psychology towards innovative conceptualization of implicit knowledge remain conceptually underdeveloped and in need of reconsideration and re-elaboration. We conclude by suggesting that the challenge of implicit cognition and nonverbal minds will only be solved through a concerted interdisciplinary approach between psychology and other disciplines.

We present empirical evidence showing that the acoustic properties of non-linguistic vocalisations produced by human infants in different cultures can be used cross-culturally by listeners to make inferences about the infant’s current behaviour. We recorded natural infant vocalisations in Scotland and Uganda in five social contexts; declarative pointing, giving an object, requesting an action, protesting, and requesting food. Using a playback paradigm, we tested parents and non-parents, who either had regular or no experience with young children, from Scotland and Uganda in their ability to match infant vocalisations of both cultures to their respective production contexts. All participants performed above chance, regardless of prior experience with infants or cultural background, with only minor differences between participant groups. Results suggest that acoustic variations in non-linguistic infant vocalisations transmit broad classes of information to listeners, even in the absence of additional cues from gesture or context, and that these cues may reflect universal properties similar to the ‘referential’ information discovered in non-human primate vocalisations.

A core component of any folk physical understanding of the world is object individuation -the cognitive ability to parse sensory input into discrete objects. Whereas younger human infants use spatio-temporal information to individuate objects, they do not use property and kind information until one year of age. Some researchers propose that object individuation based on property/kind information depends on language acquisition and sortal concepts. However, there is evidence that preverbal infants and nonhuman animals also use both types of information. The present study aimed to further explore the evolutionary origins of object individuation by testing a new-world monkey species, capuchin monkeys (Sapajus spp.), using both manual search (n = 29) and looking time (n = 23) measures. In Spatio-temporal trials, subjects saw one or two objects dropped into a box, but always found (or saw) only one. In Property/kind trials, subjects saw either object A or B being dropped into a box and then always found (or saw) object A. The capuchin monkeys looked longer and searched more on inconsistent trialswith outcome differing in quantity or in kind -which suggested that they had expectations based on both spatiotemporal and property-kind representations. Looking time and search measures gave convergent results at the group but not at the individual level. Our results add to the existing evidence contradicting the linguistic hypothesis of property/kind individuation. However, contrary to recent discussions, we argue that these and related results can be explained without appealing to the notion of sortal concepts or multiple representational systems, and suggest that a full picture of the ontogeny and phylogeny of object individuation requires further empirical and theoretical research.