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Can non-human animals combine abstract representations much like humans do with language? In particular, can they entertain a compositional representation such as ‘not blue’? Across two experiments, we demonstrate that baboons ( Papio papio ) show a capacity for compositionality. Experiment 1 showed that baboons can entertain negative, compositional, representations: they can learn to associate a cue with iconically related referents (e.g., a blue patch referring to all blue objects), but also to the complement set associated with it (e.g., a blue patch referring to all non-blue objects). Strikingly, Experiment 2 showed that baboons not only learn to associate a cue with iconically related referents, but can learn to associate complex cues (composed of the same cue and an additional visual element) with the complement object set. Thus, they can learn an operation, instantiated by this additional visual element, that can be compositionally combined with previously learned cues. These results significantly reduce any claim that would make the manipulation and combination of abstract representations a solely human privilege.

Sensory systems are permanently bombarded with complex stimuli. Cognitive processing of such complex stimuli may be facilitated by accentuation of important elements. In the case of music listening, alteration of some surface features –such as volume and duration– may facilitate the cognitive processing of otherwise high-level information, such as melody and harmony. Hence, musical accents are often aligned with intrinsically salient elements in the stimuli, such as highly unexpected notes. We developed a novel listening paradigm based on an artificial Markov-chain melodic grammar to probe the hypothesis that listeners prefer structurally salient events to be consistent with salient surface properties such as musical accents. We manipulated two types of structural saliency: one driven by Gestalt principles (a note at the peak of a melodic contour) and one driven by statistical learning (a note with high surprisal, or information content [IC], as defined by the artificial melodic grammar). Results suggest that for all listeners, the aesthetic preferences in terms of surface properties are well predicted by Gestalt principles of melodic shape. In contrast, despite demonstrating good knowledge of novel statistical properties of the melodies, participants did not demonstrate a preference for accentuation of high-IC notes. This work is a first step in elucidating the interplay between intrinsic, Gestalt-like and acquired, statistical properties of melodies in the development of expressive musical properties, with a focus on the appreciation of dynamic accents (i.e. a transient increase in volume). Our results shed light on the implementation of domain-general and domain-specific principles of information processing during music listening.

Multiple members of the tit and chickadee (= Parid) family combine two classes of calls, F and D, in a rigid order FD. In Japanese tits, FD has been argued on the basis of multiple experiments to involve syntax and non-trivial compositionality. How ancient are these call combinations? We show that FD combinations (as well as individual F and D calls) are present in nearly all Parid species, and almost absent in their closest relatives, the Remizidae and Stenostiridae. Using phylogenetic tools and ancestral reconstruction methods, we infer that FD combinations very likely emerged between 11 and 26 million years ago in the eastern Himalayas. This result contributes to evolutionary animal linguistics using a comparative phylogenetic approach to reconstruct the evolution of call combinations.

Compositionality is a means of constructing complex objects through the transformation and combination of simpler elements. While it is common to view compositionality as inherently complex, and thus to assume that compositionality is a byproduct of advanced language expertise, we argue otherwise. We propose that, although compositionality produces complex outcomes, the underlying processes are simple and can often be reduced to the general mechanism of function application. Accordingly, we explore the origins of compositionality not only in compositional language but also, and at an earlier stage, in the development of compositional representations and thoughts in young infants. Infants correctly composed simple noun-verb sentences at 14 months, facial expressions with objects at 12 months, and mental physical transformations at 10 months. This offers evidence for function application, the essence of compositionality, in infancy—emerging well before and outside the development of compositional language. A series of three studies provide evidence in infants for function application, the essence of compositionality, emerging before and outside the development of compositional language.

Recent research in infant cognition and adult vision suggests that the mechanical object relationships may be more salient and naturally attention grabbing than similar but non-mechanical relationships. Here we examine two novel sources of evidence from language related to this hypothesis. In Experiments 1 and 2, we show that adults preferentially infer that the meaning of a novel preposition refers to a mechanical as opposed to a non-mechanical relationship. Experiments 3 and 4 examine cross-linguistic adpositions obtained on a large scale from machines or from experts, respectively. While these methods differ in the ease of data collection relative to the reliability of the data, their results converge: we find that across a range of diverse and historically unrelated languages, adpositions (such as prepositions) referring to the mechanical relationships of containment (e.g \"in\") and support (e.g. \"on\") are systematically shorter than closely matched but not mechanical words such as \"behind,\" \"beside,\" \"above,\" \"over,\" \"out,\" and \"off.\" These results first suggest that languages regularly contain traces of core knowledge representations and that cross-linguistic regularities can therefore be a useful and easily accessible form of information that bears on the foundations of non-linguistic thought.

The number of potential meanings for a new word is astronomic. To make the word-learning problem tractable, one must restrict the hypothesis space. To do so, current word learning accounts often incorporate constraints about cognition or about the mature lexicon directly in the learning device. We are concerned with the convexity constraint, which holds that concepts (privileged sets of entities that we think of as \"coherent\") do not have gaps (if A and B belong to a concept, so does any entity \"between\" A and B). To leverage from it a linguistic constraint, learning algorithms have percolated this constraint from concepts, to word forms: some algorithms rely on the possibility that word forms are associated with convex sets of objects. Yet this does have to be the case: homophones are word forms associated with two separate words and meanings. Two sets of experiments show that when evidence suggests that a novel label is associated with a disjoint (non-convex) set of objects, either a) because there is a gap in conceptual space between the learning exemplars for a given word or b) because of the intervention of other lexical items in that gap, adults prefer to postulate homophony, where a single word form is associated with two separate words and meanings, rather than inferring that the word could have a disjunctive, discontinuous meaning. These results about homophony must be integrated to current word learning algorithms. We conclude by arguing for a weaker specialization of word learning algorithms, which too often could miss important constraints by focusing on a restricted empirical basis (e.g., non-homophonous content words).

Using field observations from a sanctuary, Oña and colleagues (DOI: 10.7717/peerj.7623 ) investigated the semantics of face-gesture combinations in chimpanzees ( Pan troglodytes ). The response of the animals to these signals was encoded as a binary measure: positive interactions such as approaching or grooming were considered affiliative; ignoring or attacking was considered non-affiliative. The relevant signals are illustrated in Fig. 1 ( https://doi.org/10.7717/peerj.7623/fig-1 ), together with the outcome in terms of average affiliativeness. The authors observe that there seems to be no systematicity in the way the faces modify the responses to the gestures, sometimes reducing affiliativeness, sometimes increasing it. A strong interpretation of this result would be that the meaning of a gesture-face combination cannot be derived from the meaning of the gesture and the meaning of the face, that is, the interpretation of chimpanzees’ face-gesture combinations are non compositional in nature. We will revisit this conclusion: we will exhibit simple compositional systems which, after all, may be plausible. At the methodological level, we argue that it is critical to lay out the theoretical options explicitly for a complete comparison of their pros and cons.

We train neural networks to optimize a Minimum Description Length score, that is, to balance between the complexity of the network and its accuracy at a task. We show that networks optimizing this objective function master tasks involving memory challenges and go beyond context-free languages. These learners master languages such as , , , , and they perform addition. Moreover, they often do so with 100% accuracy. The networks are small, and their inner workings are transparent. We thus provide formal proofs that their perfect accuracy holds not only on a given test set, but for any input sequence. To our knowledge, no other connectionist model has been shown to capture the underlying grammars for these languages in full generality.

Sprouse and Almeida (2017) provide a first systematic investigation of the sensitivity of four acceptability judgment tasks. In this project, we build on these results by decomposing those tasks into three constituent task features (single versus joint presentation, number of response options, and use of response labels), and explore the consequences of those task features on the sensitivity of acceptability judgment experiments. We present 6 additional experiments (for a total of 10) designed to probe the effect of those task features on sensitivity, both independently and in combination. Our results suggest three notable conclusions: (i) there is a clear advantage to joint presentation of theoretically-related sentence types, regardless of the type of response scale used in the experiment; (ii) tasks involving a continuous slider (which have an infinite number of response options, and few labels) offer good sensitivity, while relying solely on spatial reasoning rather than numeric reasoning; and (iii) there are a number of subtle interactions among the three task features that may warrant further investigation. We discuss the potential benefits and concerns of each of these features in detail, along with the relevance of these findings for deciding how to investigate both simple and higher-order acceptability contrasts.

Emotive-factive predicates, such as surprise or be happy, are a source of empirical and theoretical puzzles in the literature on embedded questions. Although they embed wh-questions, they seem not to embed whether-questions. They have complex interactions with negative polarity items such as any or even, and they have been argued to preferentially give rise to weakly exhaustive readings with embedded questions (in contrasts with most other verbs, which have been argued to give rise to strongly exhaustive readings). We offer an empirical overview of the situation in three experiments collecting acceptability judgments, monotonicity judgments, and truth-value judgments. The results straightforwardly confirm the special selectional properties of emotive-factive predicates. More interestingly, they reveal the existence of strongly exhaustive readings for surprise. The results also suggest that the special properties of emotive-factives cannot be solely explained by their monotonicity profiles, because they were not found to differ from the profiles of other responsive predicates.