School of Social Sciences, Humanities, and Arts

Parent-child dyads in which the child is deaf but the parent is hearing present a unique opportunity to examine parents’ use of non-auditory cues, particularly vision and touch, to establish communicative intent. This study examines the multimodal communication patterns of hearing parents during a free play task with their hearing (N=9) or deaf (N=9) children. Specifically, we coded parents’ use of multimodal cues in the service of establishing joint attention with their children. Dyad types were compared for overall use of multimodal – auditory, visual, and tactile – attention-establishing cues, and for the overall number of successful and failed bids by a parent for a child’s attention. The relationship between multimodal behaviors on the part of the parent were tracked for whether they resulted in successful or failed initiation of joint attention. We focus our interpretation of the results on how hearing parents differentially accommodate their hearing and deaf children to engage them in joint attention. Findings can inform the development of recommendations for hearing parents of deaf children who are candidates for cochlear implantation regarding communication strategies to use prior to a child’s implantation. Moreover, these findings expand our understanding of how joint attention is established between parents and their preverbal children, regardless of children’s hearing status.

According to the cross-situational learning account, infants aggregate statistical information from multiple parent naming events to resolve ambiguous word-referent mappings within individual naming events. While previous experimental studies have shown that infant and adult learners can build correct mappings based on statistical regularities encoded in multiple learning situations in an experiment, other studies that use more naturalistic stimuli (e.g., real-world video) reveal poor performance in adults' ability to infer the correct referent. Based on those results derived from more naturalistic stimuli, the cross-situational learning solution cannot be useful to solve the mapping problem in the real world because cross-situational statistics from the real world are much more ambiguous than those created in experimental studies. To examine the feasibility of cross-situational learning in everyday contexts, the present study aims to quantify visual-audio statistics from one of everyday activities-parent-child toy play. We analyze parent naming events in a video corpus of infant-perspective scenes during parent-child toy play in a naturalistic lab setting, where we found three distinct properties that characterize statistical regularities perceived by young learners: (1) there are a limited number of visual scene compositions perceived by young learners at the moments when they hear object names; (2) the frequencies of parent naming events are distributed in a skewed, Zipfian fashion; and (3) cross-situational statistics in naturalistic toy play are comparable to those used in laboratory experiments. Our results underscore the importance of quantifying the statistical regularities in the input from the learner's perspective in order to shed light on the mechanisms supporting early word learning.

Music traditions worldwide are subject to remarkable diversity but the origins of this variation are not well understood. Musical behaviour is the product of a multicomponent collection of abilities, some possibly evolved for music but most derived from traits serving nonmusical functions. Cultural evolution has stitched together these systems, generating variable normative practices across cultures and musical genres. Here, we describe the cultural evolution of musical distortion, a noisy manipulation of instrumental and vocal timbre that emulates nonlinear phenomena (NLP) present in the vocal signals of many animals. We suggest that listeners sensitivity to NLP has facilitated technological developments for altering musical instruments and singing with distortion, which continues to evolve culturally via the need for groups to both coordinate internally and differentiate themselves from other groups. To support this idea, we present an agent-based model of norm evolution illustrating possible dynamics of continuous traits such as timbral distortion in music, dependent on (i) a functional optimum, (ii) intra-group cohesion and inter-group differentiation and (iii) groupishness for assortment and social learning. This account illustrates how cultural transmission dynamics can lead to diversity in musical sounds and genres, and also provides a more general explanation for the emergence of subgroup-differentiating norms.This article is part of the theme issue Nonlinear phenomena in vertebrate vocalizations: mechanisms and communicative functions.

Conversational partners align the meanings of their words over the course of interaction to coordinate and communicate. One process of alignment is lexical entrainment, whereby partners mirror and abbreviate their word usage to converge on shared terms for referents relevant to the conversation. However, lexical entrainment may result in inefficient mimicry that does not add new information, suggesting that task-oriented communication may favor alignment through other means. The present study investigates the process of alignment in Danish conversations in which dyads learned to categorize unfamiliar "aliens" using trial-and-error feedback. Performance improved as dyad communication became less verbose, measured as a decrease in the entropy of word usage. Word usage also diverged between partners as measured by Jensen-Shannon Divergence, which indicates that alignment was not achieved through lexical entrainment. A computational model of dyadic communication is shown to account for the alien game results in terms of joint least effort. The model shows that alignment of partner referents can increase as a result of minimizing both the joint entropy of dyadic word usage and the conditional entropy of individual referents given the joint signal distribution. We conclude that the principle of least effort, originally proposed to shape language evolution, may also support alignment in task-oriented communication.

The control of human balance involves an interaction between the human motor, cognitive, and sensory systems. The dynamics of this interaction are yet to be fully understood, however, work has shown the performance of cognitive tasks to have a hampering effect on motor performance, while additive sensory noise to have a beneficial effect. The current study aims to examine whether postural control will be impacted by a concurrent working memory task, and similarly, if additive noise can counteract the expected negative influence of the added cognitive demand. Postural sway of healthy young adults was collected during the performance of a modified N-back task with varying difficulty, in the presence and absence of auditory noise. Our results show a reduction in postural stability scaled to the difficulty of the cognitive task, but this effect is less prominent in the presence of additive noise. Additionally, by separating postural sway into different frequency bands, typically used to assess the exploratory vs feedback-driven stabilizing dynamics of sway, we found a differential effect between the cognitive task and additive noise, thus demonstrating that both frequency regimes of postural sway are sensitive to high cognitive load and increased sensory information.

Individuals with "agrammatic" receptive aphasia have long been known to rely on semantic plausibility rather than syntactic cues when interpreting sentences. In contrast to early interpretations of this pattern as indicative of a deficit in syntactic knowledge, a recent proposal views agrammatic comprehension as a case of "noisy-channel" language processing with an increased expectation of noise in the input relative to healthy adults. Here, we investigate the nature of the noise model in aphasia and whether it is adapted to the statistics of the environment. We first replicate findings that a) healthy adults (N = 40) make inferences about the intended meaning of a sentence by weighing the prior probability of an intended sentence against the likelihood of a noise corruption and b) their estimate of the probability of noise increases when there are more errors in the input (manipulated via exposure sentences). We then extend prior findings that adults with chronic post-stroke aphasia (N = 28) and healthy age-matched adults (N = 19) similarly engage in noisy-channel inference during comprehension. We use a hierarchical latent mixture modeling approach to account for the fact that rates of guessing are likely to differ between healthy controls and individuals with aphasia and capture individual differences in the tendency to make inferences. We show that individuals with aphasia are more likely than healthy controls to draw noisy-channel inferences when interpreting semantically implausible sentences, even when group differences in the tendency to guess are accounted for. While healthy adults rapidly adapt their inference rates to an increase in noise in their input, whether individuals with aphasia do the same remains equivocal. Further investigation of comprehension through a noisy-channel lens holds promise for a parsimonious understanding of language processing in aphasia and may suggest potential avenues for treatment.

Humans often learn preferentially from ingroup members who share a social identity affiliation, while ignoring or rejecting information when it comes from someone perceived to be from an outgroup. This sort of bias has well-known negative consequences - exacerbating cultural divides, polarization, and conflict - while reducing the information available to learners. Why does it persist? Using evolutionary simulations, we demonstrate that similarity-biased social learning (also called parochial social learning) is adaptive when (1) individual learning is error-prone and (2) sufficient diversity inhibits the efficacy of social learning that ignores identity signals, as long as (3) those signals are sufficiently reliable indicators of adaptive behaviour. We further show that our results are robust to considerations of other social learning strategies, focusing on conformist and pay-off-biased transmission. We conclude by discussing the consequences of our analyses for understanding diversity in the modern world.

A sequence of technological inventions over several centuries has dramatically lowered the cost of producing and distributing information. Because societies ride on a substrate of information, these changes have profoundly impacted how we live, work, and interact. This paper explores the nature of information architectures (IAs)-the features that govern how information flows within human populations. IAs include physical and digital infrastructures, norms and institutions, and algorithmic technologies for filtering, producing, and disseminating information. IAs can reinforce societal biases and lead to prosocial outcomes as well as social ills. IAs have culturally evolved rapidly with human usage, creating new affordances and new problems for the dynamics of social interaction. We explore societal outcomes instigated by shifts in IAs and call for an enhanced understanding of the social implications of increasing IA complexity, the nature of competition among IAs, and the creation of mechanisms for the beneficial use of IAs.