Common marmosets are sensitive to simple dependencies at variable distances in an artificial grammar

Abstract

Recognizing that two elements within a sequence of variable length depend on each other is a key ability in understanding the structure of language and music. Perception of such interdependencies has previously been documented in chimpanzees in the visual domain and in human infants and common squirrel monkeys with auditory playback experiments, but it remains unclear whether it typifies primates in general. Here, we investigated the ability of common marmosets ( Callithrix jacchus ) to recognize and respond to such dependencies. We tested subjects in a familiarization-discrimination playback experiment using stimuli composed of pure tones that either conformed or did not conform to a grammatical rule. After familiarization to sequences with dependencies, marmosets spontaneously discriminated between sequences containing and lacking dependencies (‘consistent’ and ‘inconsistent’, respectively), independent of stimulus length. Marmosets looked more often to the sound source when hearing sequences consistent with the familiarization stimuli, as previously found in human infants. Crucially, looks were coded automatically by computer software, avoiding human bias. Our results support the hypothesis that the ability to perceive dependencies at variable distances was already present in the common ancestor of all anthropoid primates ( Simiiformes ).

Breaking conversational rules matters to captive gorillas: A playback experiment

“…when vocalisation and video matched) 66 . A stronger attentional state towards an expected vocal sequence pattern rather than an unexpected one was also found in common marmosets 67 . Thus, the direction of the subjects' attention bias in such experimental paradigms may be stimulus-or context-dependent.…”

Nonadjacent dependency processing in monkeys, apes, and humans

“…For example, a number of paradigms used passive learning of grammars [e.g., cotton-top tamarins, Saguinus oedipus ( 8 , 24 ); squirrel monkeys, Saimiri sciureus ( 5 )], while others actively trained subjects via operant conditioning [e.g., starlings, Sturnus vulgaris ( 35 ); rhesus macaques, Macaca mulatta ( 9 )]. In addition, some studies investigated sequence processing in the visual [e.g., chimpanzees ( 15 , 16 ); rats, Rattus norvegicus ( 36 ); cotton-top tamarins ( 12 )] rather than auditory domain [e.g., Bengalese finches, Lonchura striata domestica ( 14 )], and certain studies constructed their grammars from artificial stimuli [e.g., squirrel monkeys and common marmosets ( 5 , 6 )] as opposed to using vocalizations from the study species’ own repertoire [e.g., starlings ( 13 , 35 )]. While experimental design must account for the pertinent cognitive, behavioral, and morphological profiles of a study species, it is advantageous to keep all other factors as similar as possible when aiming to facilitate fair comparisons across species ( 19 – 23 ).…”

“…An emerging body of data from “artificial grammar” experiments, where subjects must compute predictive relationships between elements in strings of stimuli organized according to grammatical rules ( 3 , 4 ), suggests that some species of monkey have the capacity to process Non-ADs in both auditory ( 5 – 8 ) and visual modalities ( 9 – 12 ). This has been argued to indicate an evolutionary continuity of the human capacity for Non-AD processing, traceable perhaps as far back as the last common ancestor of anthropoid primates ( 6 ). However, given the phylogenetic distance between New World monkeys and humans (approximately 40 million years ago), it is currently unclear whether this capacity is really ancestral or a product of convergent evolution.…”

A conveyor feeder for animal experiments

“…Automated devices have been used for animal experiments in many scientific fields such as cognitive biology, neuroscience, ethology and psychology to test cognitive abilities and measure behaviors [1,2,3,4,5,6,7]. Also, open source devices have been increasingly used in these fields to facilitate reproduction, validation and customization [8,9,10].…”

“…The glue gun was used to fortify the attachment and cover sharp ends of the wire (the 7th and 8th image of Figure 2). The process of this attachment, (4)(5)(6)(7)(8), is also shown in a video, 'f c2B.mp4' uploaded to https://osfi.io/kgrm9/. The distance between two containers (from top of a container to top of the next container) was approximately four centimetres.…”