Heidi Lyn

The Impact of Environment on the Comprehension of Declarative Communication in Apes

A series of recent reports have questioned the ability of great apes to comprehend declarative communication and have suggested that this ability is biologically based and may have driven the evolution of human language. We tested three groups of differently reared chimpanzees and bonobos for their ability to understand declarative signals in an object-choice task. The scores of the two groups of apes that were reared in a sociolinguistically complex environment were significantly higher than the scores of the standard-reared group. The results further showed that bonobos did not outperform chimpanzees. Our results demonstrate that environmental factors, particularly access to a sociolinguistically rich environment, directly influence great apes’ ability to comprehend declarative signals and suggest that, contrary to recent claims, apes have the biological capacity to utilize purely informative communication.

Planum temporale grey matter asymmetries in chimpanzees (Pan troglodytes), vervet (Chlorocebus aethiops sabaeus), rhesus (Macaca mulatta) and bonnet (Macaca radiata) monkeys

Brain asymmetries, particularly asymmetries within regions associated with language, have been suggested as a key difference between humans and our nearest ancestors. These regions include the planum temporale (PT) - the bank of tissue that lies posterior to Heschls gyrus and encompasses Wernickes area, an important brain region involved in language and speech in the human brain. In the human brain, both the surface area and the grey matter volume of the PT are larger in the left compared to right hemisphere, particularly among right-handed individuals. Here we compared the grey matter volume and asymmetry of the PT in chimpanzees and three other species of nonhuman primate in two Genera including vervet monkeys (Chlorocebus aethiops sabaeus), rhesus macaques (Macaca mulatta) and bonnet macaques (Macaca radiata). We show that the three monkey species do not show population-level asymmetries in this region whereas the chimpanzees do, suggesting that the evolutionary brain development that gave rise to PT asymmetry occurred after our split with the monkey species, but before our split with the chimpanzees.

Volumetric and Lateralized Differences in Selected Brain Regions of Chimpanzees (Pan troglodytes) and Bonobos (Pan paniscus)

The two species of Pan, bonobos and common chimpanzees, have been reported to have different social organization, cognitive and linguistic abilities and motor skill, despite their close biological relationship. Here, we examined whether bonobos and chimpanzee differ in selected brain regions that may map to these different social and cognitive abilities. Eight chimpanzees and eight bonobos matched on age, sex and rearing experiences were magnetic resonance images scanned and volumetric measures were obtained for the whole brain, cerebellum, striatum, motor‐hand area, hippocampus, inferior frontal gyrus and planum temporale. Chimpanzees had significantly larger cerebellum and borderline significantly larger hippocampus and putamen, after adjusting for brain size, compared with bonobos. Bonobos showed greater leftward asymmetries in the striatum and motor‐hand area compared with chimpanzees. No significant differences in either the volume or lateralization for the so‐called language homologs were found between species. The results suggest that the two species of Pan are quite similar neurologically, though some volumetric and lateralized differences may reflect inherent differences in social organization, cognition and motor skills. Am. J. Primatol. 71:988–997, 2009.

Observational word learning in two bonobos (Pan paniscus): ostensive and non-ostensive contexts

Word learning has been extensively studied in humans. Children seem to be able to map new words onto objects with only one exposure to the referent. This ability has been called ‘‘fast mapping’’(Carey, 1978; Carey and Bartlett, 1978). Using a modified human paradigm, this paper explores two language-competent bonobos’ (Pan paniscus) abilities to map new words to objects in realistic surroundings with few exposures to the referents. This paper also investigates the necessity of the apes maintaining visual contact (ostensive context) with the item to map the novel name onto the novel object. The bonobos tested in this experiment were able to map new words onto objects and could do so without visual contact with the items. # 2000 Elsevier Science Ltd. All rights reserved.

Apes communicate about absent and displaced objects: methodology matters

Displaced reference is the ability to refer to an item that has been moved (displaced) in space and/or time, and has been called one of the true hallmarks of referential communication. Several studies suggest that nonhuman primates have this capability, but a recent experiment concluded that in a specific situation (absent entities), human infants display displaced reference but chimpanzees do not. Here, we show that chimpanzees and bonobos of diverse rearing histories are capable of displaced reference to absent and displaced objects. It is likely that some of the conflicting findings from animal cognition studies are due to relatively minor methodological differences, but are compounded by interpretation errors. Comparative studies are of great importance in elucidating the evolution of human cognition; however, greater care must be taken with methodology and interpretation for these studies to accurately reflect species differences.

Environment, methodology, and the object choice task in apes: Evidence for declarative comprehension and implications for the evolution of language

Abstract The ability to comprehend purely informative (declarative) communications has been put forward by several researchers as a possible biological distinction between humans and our nearest evolutionary relatives, the great apes. Most studies that purport to show that great apes cannot comprehend declaratives utilize the object choice task as a basis of measurement and have relatively few subjects. Here we report on a large-scale study of chimpanzees and bonobos as well as a meta-analysis of earlier studies. The data from this large pool of subjects suggest that environmental and methodological differences greatly affect the ability of great apes on the object choice task. Therefore, it is unlikely that an adaptation for declarative comprehension drove the evolution of human language.

Gestural and symbolic development among apes and humans: support for a multimodal theory of language evolution

What are the implications of similarities and differences in the gestural and symbolic development of apes and humans?This focused review uses as a starting point our recent study that provided evidence that gesture supported the symbolic development of a chimpanzee, a bonobo, and a human child reared in language-enriched environments at comparable stages of communicative development. These three species constitute a complete clade, species possessing a common immediate ancestor. Communicative behaviors observed among all species in a clade are likely to have been present in the common ancestor. Similarities in the form and function of many gestures produced by the chimpanzee, bonobo, and human child suggest that shared non-verbal skills may underlie shared symbolic capacities. Indeed, an ontogenetic sequence from gesture to symbol was present across the clade but more pronounced in child than ape. Multimodal expressions of communicative intent (e.g., vocalization plus persistence or eye-contact) were normative for the child, but less common for the apes. These findings suggest that increasing multimodal expression of communicative intent may have supported the emergence of language among the ancestors of humans. Therefore, this focused review includes new studies, since our 2013 article, that support a multimodal theory of language evolution.

A Cross-Species Study of Gesture and Its Role in Symbolic Development: Implications for the Gestural Theory of Language Evolution

Using a naturalistic video database, we examined whether gestures scaffold the symbolic development of a language-enculturated chimpanzee, a language-enculturated bonobo, and a human child during the second year of life. These three species constitute a complete clade: species possessing a common immediate ancestor. A basic finding was the functional and formal similarity of many gestures between chimpanzee, bonobo, and human child. The child’s symbols were spoken words; the apes’ symbols were lexigrams – non-iconic visual signifiers. A developmental pattern in which gestural representation of a referent preceded symbolic representation of the same referent appeared in all three species (but was statistically significant only for the child). Nonetheless, across species, the ratio of symbol to gesture increased significantly with age. But even though their symbol production increased, the apes continued to communicate more frequently by gesture than by symbol. In contrast, by 15–18 months of age, the child used symbols more frequently than gestures. This ontogenetic sequence from gesture to symbol, present across the clade but more pronounced in child than ape, provides support for the role of gesture in language evolution. In all three species, the overwhelming majority of gestures were communicative (i.e., paired with eye contact, vocalization, and/or persistence). However, vocalization was rare for the apes, but accompanied the majority of the child’s communicative gestures. This species difference suggests the co-evolution of speech and gesture after the evolutionary divergence of the hominid line. Multimodal expressions of communicative intent (e.g., vocalization plus persistence) were normative for the child, but less common for the apes. This species difference suggests that multimodal expression of communicative intent was also strengthened after hominids diverged from apes.

Semiotic combinations in Pan: A comparison of communication in a chimpanzee and two bonobos

Communicative combinations of two bonobos (Pan paniscus) and a chimpanzee (Pan troglodytes) are compared. All three apes utilized ordering strategies for combining symbols (lexigrams) or a lexigram with a gesture to express semantic relations such as agent of action or object of action. Combinatorial strategies used by all three apes revealed commonalities with child language, spoken and signed, at the two-year-old level. However, many differences were also observed: e.g., combinations made up a much smaller proportion and single symbols a much larger proportion of ape production compared with child production at a similar age; and ape combinations rarely exceeded three semiotic elements. The commonalties and differences among three sibling species highlight candidate combinatorial capacities that may underlie the evolution of human language.

The influence of feeding, enrichment, and seasonal context on the behavior of Pacific Walruses (Odobenus rosmarus divergens)

Though some research exists concerning general behavior and activity patterns of Walruses in zoos or aquariums, less is known about how these patterns change in response to various environmental and temporal contexts. This study presents two studies assessing behavioral changes in relation to feeding period, object enrichment (OE), and season in a social group of four Pacific Walruses at the New York Aquarium. Study 1 examined behavior in relation to feeding context (nonfeed, prefeed, postfeed); data were collected over a three-week period, resulting in 47 observation sessions for each feeding context. Study 2 examined behavior in relation to OE and season; data were collected in two phases resulting in 12 enrichment and 9 no-enrichment (NE) observation sessions (Phase 1), and 21 enrichment and 18 NE observation sessions (Phase 2). Study 1 showed that after feeding, oral behavior increased while social behavior and total swim frequency decreased. In Study 2, both swim frequency and social behavior were found to interact with OE and phase, while oral behavior remained constant across all conditions. As in the wild, both studies found all animals to be swimming the majority of the time. Though every animal spent much of its swim time engaged in an Individual Swimming Pattern (ISP), both studies showed that the proportion of ISP (in relation to total time swimming) remained stable across all contexts, suggesting a potential functional role of the ISPs. These results are discussed in light of the ongoing debate over the role of stereotypies in welfare assessment.