How arbitrary is language?

Effects of Systematicity on Word Learning in Preschool Children: The Case of Semitic Morpho-Phonology

This study investigated the role of systematicity in word learning, focusing on Semitic morpho-phonology where words exhibit multiple levels of systematicity. Building upon previous research on phonological templates, we explored how systematicity based on such templates, whether they encode meanings or not, influenced word learning in preschool-age Hebrew-speaking children. We examined form-meaning systematicity, where words share phonological templates and carry similar categorical meanings of manner-of-motion (e.g., finupál and bizudáx carry the meaning of skipping), and form-only systematicity, where words are phonologically similar but do not share a meaning (e.g., finupál and bizudáx belong to different categories of manner-of-motion). We aimed to discern how these systematicity types impact the learning of the meaning of the word as a whole, that is, the encoding of visual form combined with manner-of-motion. Using novel Semitic-like stimuli, our experiments demonstrated that different types of systematicity involve different effects on word learning. Experiment 1 showed that form-meaning systematicity hindered the learning of the manner-of-motion. In contrast, Experiment 2 revealed that form systematicity facilitated learning these features. The findings suggest a complex interplay of top-down and bottom-up processes in word learning, expanding our understanding of systematicity in word learning.

Gestural Iconicity and Alignment as Steps in the Evolution of Language

Studies of the evolution of language rely heavily on comparisons to nonhuman primates, particularly the gestural communication of nonhuman apes. Differences between human and ape gestures are largely ones of degree rather than kind. For example, while human gestures are more flexible, ape gestures are not inflexible. In this piece, I closely consider two features of the gestural communication of apes and humans that might display differences in kind: iconicity and temporal alignment. Iconicity has long played a privileged role in theories of gestural language origins, the proposal being that it provided a steppingstone into language through a stage of pantomime. However, iconicity is not as easy as it seems. Evidence from co-speech gestures of hearing children and from homesign suggests that iconic reference is both cognitively complex and slow to develop in humans. There is no conclusive evidence that nonhuman apes understand or produce iconic gestures; some gestures may appear iconic to human observers but the apes themselves may not understand the similarity between form and meaning. Far from providing an easy pathway into the emergence of symbolic communication, iconicity relies on sophisticated capacities for analogy and abstraction, ones often lacking in apes and young children. Temporal alignment between gesture and vocalization is another area that may show sharp contrasts between adult humans and apes, though data here is sparser. I discuss the tight synchronization of gesture and speech that emerges over the first year of life in human children and contrast it with gesture and vocalization in apes, which typically are described as overlapping but not simultaneous. Human ancestors probably communicated in ways similar to other apes, but the dual emergence of the ability to use iconic reference and the alignment of hand and mouth may have set our ancestors down a unique evolutionary road toward language.

The affective iconicity of lexical tone: Evidence from standard Chinesea)

Previous studies suggested that pitch characteristics of lexical tones in Standard Chinese influence various sensory perceptions, but whether they iconically bias emotional experience remained unclear. We analyzed the arousal and valence ratings of bi-syllabic words in two corpora (Study 1) and conducted an affect rating experiment using a carefully designed corpus of bi-syllabic words (Study 2). Two-alternative forced-choice tasks further tested the robustness of lexical tones' affective iconicity in an auditory nonce word context (Study 3). Hierarchical linear models, generalized linear mixed models, and cross-validation were employed to understand the relationship between lexical tones and the emotional responses of tone-carrying words. Results consistently indicated that words with a falling-falling tonal sequence, both real and nonce words, received higher arousal ratings than those with rising-rising and rising-low tones. Only in nonce words, the high-high sequence was more likely to be associated with the low-arousal option; the falling-falling tone sequence was more often linked to negative-valence choice, while high-high and rising-rising tones with positive-valence. These findings, though subtle, suggest that the use of pitch in lexical tones influences emotional responses during the processing of tone-carrying words, pointing to an inherent iconic quality in lexical tones that may subtly shape speakers' emotional experiences.

Human-machine interactions with clinical phrase prediction system, aligning with Zipf's least effort principle?

The essence of language and its evolutionary determinants have long been research subjects with multifaceted explorations. This work reports on a large-scale observational study focused on the language use of clinicians interacting with a phrase prediction system in a clinical setting. By adopting principles of adaptation to evolutionary selection pressure, we attempt to identify the major determinants of language emergence specific to this context. The observed adaptation of clinicians' language behaviour with technology have been confronted to properties shaping language use, and more specifically on two driving forces: conciseness and distinctiveness. Our results suggest that users tailor their interactions to meet these specific forces to minimise the effort required to achieve their objective. At the same time, the study shows that the optimisation is mainly driven by the distinctive nature of interactions, favouring communication accuracy over ease. These results, published for the first time on a large-scale observational study to our knowledge, offer novel fundamental qualitative and quantitative insights into the mechanisms underlying linguistic behaviour among clinicians and its potential implications for language adaptation in human-machine interactions.

Forms, Mechanisms, and Roles of Iconicity in Spoken Language: A Review

Historically, debates over relationships between spoken lexical form and meaning have been dominated by views of arbitrariness. However more recent research revealed a different perspective, in which non-arbitrary mappings play an important role in the makeup of a lexicon. It is now clear that phoneme-sound symbolism - along with other types of form-to-meaning mappings - contributes to non-arbitrariness (iconicity) of spoken words, which is present in many forms and degrees in different languages. Attempts have been made to provide a mechanistic explanation of the phenomenon, and these theories largely centre around cross-modal correspondences. We build on these views to explore iconicity within the evolutionary context and the neurobiological framework for human language processing. We argue that the multimodal bihemsipheric communicative system, to which iconicity is integral, has important phylogenetic and ontogenetic advantages, facilitating language learning, comprehension, and processing. Despite its numerous advantages however, iconicity must compete with arbitrariness, forcing language systems to balance the competing needs of perceptual grounding of the linguistic form and ensuring an effective signal. We conclude that, on balance, iconicity should be viewed as integral to language, and not merely a marginal phenomenon.

The evolution of human music in light of increased prosocial behavior: a new model

Together with language, music is perhaps our most distinctive behavioral trait. Following the lead of evolutionary linguistic research, different hypotheses have been proposed to explain why only humans perform music and how this ability might have evolved in the species. In this paper, we advance a new model of music evolution that builds on the theory of self-domestication, according to which the human phenotype is, at least in part, the outcome of a process similar to mammal domestication, triggered by a progressive reduction in reactive aggression levels in response to environmental changes. In the paper, we specifically argue that changes in aggression management through the course of human cultural evolution can account for the behaviors conducive to the emergence and evolution of music. We hypothesize 4 stages in the evolutionary development of music under the influence of environmental changes and evolution of social organization: starting from musilanguage, 1) proto-music gave rise to 2) personal and private forms of timbre-oriented music, then to 3) small-group ensembles of pitch-oriented music, at first of indefinite and then definite pitch, and finally to 4) collective (tonal) music. These stages parallel what has been hypothesized for languages and encompass the diversity of music types and genres described worldwide. Overall, music complexity emerges in a gradual fashion under the effects of enhanced abilities for cultural niche construction, resulting from the stable trend of reduction in reactive aggression towards the end of the Pleistocene, leading to the rise of hospitality codes, and succeeded by the increase in proactive aggression from the beginning of the Holocene onward. This paper addresses numerous controversies in the literature on the evolution of music by providing a clear structural definition of music, identifying its structural features that distinguish it from oral language, and summarizing the typology of operational functions of music and formats of its transmission. The proposed framework of structural approach to music arms a researcher with means to identify and comparatively analyze different schemes of tonal organization of music, placing them in the context of human social and cultural evolution. Especially valuable is the theory of so-called "personal song", described and analyzed here from ethological, social, cultural, cognitive, and musicological perspectives. Personal song seems to constitute a remnant of the proto-musical transition from animal communication to human music as we know it today. We interlink the emergence of personal song with the evolution of kinship, placing both of them on the timeline of cultural evolution - based on totality of ethnographic, archaeological, anthropological, genetic, and paleoclimatic data.

Revisiting the concreteness effect: Non-arbitrary mappings between form and concreteness of English words influence lexical processing

How do we represent and process abstract and concrete concepts? The "concreteness effect", in which words with more concrete meanings are processed more quickly and accurately across a range of language tasks compared to abstract ones, suggests a differential conceptual organization of these words in the brain. However, concrete words tend to be marked by specific phonotactic features, such as having fewer syllables and more phonological neighbours. It is unclear whether these non-arbitrary form-meaning relationships that systematically denote the concreteness of a word impact language processing. In the current study, we first establish the extent of systematic mappings between phonological/phonetic features and concreteness ratings in a large set of monosyllabic and polysyllabic English words (i.e., concreteness form typicality), then demonstrate that they significantly influence lexical processing using behavioural megastudy datasets. Surface form features predicted a significant proportion of variance in concreteness ratings of monomorphemic words (25 %) which increased with the addition of polymorphemic forms (43 %). In addition, concreteness form typicality was a significant predictor of performance on visual and auditory lexical decision, naming, and semantic (concrete/abstract) decision tasks, after controlling for a range of psycholinguistic variables and concreteness ratings. Overall, our results provide the first evidence that concreteness form typicality influences lexical processing. We discuss theoretical implications for interpretations of the concreteness effect and models of language processing that have yet to incorporate non-arbitrary relationships between form and meaning into their feature sets.

Do 14-17-month-old infants use iconic speech and gesture cues to interpret word meanings?a)

This experimental study investigated whether infants use iconicity in speech and gesture cues to interpret word meanings. Specifically, we tested infants' sensitivity to size sound symbolism and iconic gesture cues and asked whether combining these cues in a multimodal fashion would enhance infants' sensitivity in a superadditive manner. Thirty-six 14-17-month-old infants participated in a preferential looking task in which they heard a spoken nonword (e.g., "zudzud") while observing a small and large object (e.g., a small and large square). All infants were presented with an iconic cue for object size (small or large) (1) in the pitch of the spoken non-word (high vs low), (2) in gesture (small or large), or (3) congruently in pitch and gesture (e.g., a high pitch and small gesture indicating a small square). Infants did not show a preference for congruently sized objects in any iconic cue condition. Bayes factor analyses showed moderate to strong support for the null hypotheses. In conclusion, 14-17-month-old infants did not use iconic pitch cues, iconic gesture cues, or iconic multimodal cues (pitch and gesture) to associate speech sounds with their referents. These findings challenge theories that emphasize the role of iconicity in early language development.

Sound symbolic associations in Spanish emotional words: affective dimensions and discrete emotions

Sound symbolism refers to non-arbitrary associations between word forms and meaning, such as those observed for some properties of sounds and size or shape. Recent evidence suggests that these connections extend to emotional concepts. Here we investigated two types of non-arbitrary relationships. Study 1 examined whether iconicity scores (i.e. resemblance-based mapping between aspects of a word's form and its meaning) for words can be predicted from ratings in the affective dimensions of valence and arousal and/or the discrete emotions of happiness, anger, fear, disgust and sadness. Words denoting negative concepts were more likely to have more iconic word forms. Study 2 explored whether statistical regularities in single phonemes (i.e. systematicity) predicted ratings in affective dimensions and/or discrete emotions. Voiceless (/p/, /t/) and voiced plosives (/b/, /d/, /g/) were related to high arousing words, whereas high arousing negative words tended to include fricatives (/s/, /z/). Hissing consonants were also more likely to occur in words denoting all negative discrete emotions. Additionally, words conveying certain discrete emotions included specific phonemes. Overall, our data suggest that emotional features might explain variations in iconicity and provide new insight about phonemic patterns showing sound symbolic associations with the affective properties of words.

Systematic mappings of sound to meaning: A theoretical review

The form of a word sometimes conveys semantic information. For example, the iconic word gurgle sounds like what it means, and busy is easy to identify as an English adjective because it ends in -y. Such links between form and meaning matter because they help people learn and use language. But gurgle also sounds like gargle and burble, and the -y in busy is morphologically and etymologically unrelated to the -y in crazy and watery. Whatever processing effects gurgle and busy have in common likely stem not from iconic, morphological, or etymological relationships but from systematicity more broadly: the phenomenon whereby semantically related words share a phonological or orthographic feature. In this review, we evaluate corpus evidence that spoken languages are systematic (even when controlling for iconicity, morphology, and etymology) and experimental evidence that systematicity impacts word processing (even in lieu of iconic, morphological, and etymological relationships). We conclude by drawing attention to the relationship between systematicity and low-frequency words and, consequently, the role that systematicity plays in natural language processing.

High-level language brain regions process sublexical regularities

A network of left frontal and temporal brain regions supports language processing. This "core" language network stores our knowledge of words and constructions as well as constraints on how those combine to form sentences. However, our linguistic knowledge additionally includes information about phonemes and how they combine to form phonemic clusters, syllables, and words. Are phoneme combinatorics also represented in these language regions? Across five functional magnetic resonance imaging experiments, we investigated the sensitivity of high-level language processing brain regions to sublexical linguistic regularities by examining responses to diverse nonwords-sequences of phonemes that do not constitute real words (e.g. punes, silory, flope). We establish robust responses in the language network to visually (experiment 1a, n = 605) and auditorily (experiments 1b, n = 12, and 1c, n = 13) presented nonwords. In experiment 2 (n = 16), we find stronger responses to nonwords that are more well-formed, i.e. obey the phoneme-combinatorial constraints of English. Finally, in experiment 3 (n = 14), we provide suggestive evidence that the responses in experiments 1 and 2 are not due to the activation of real words that share some phonology with the nonwords. The results suggest that sublexical regularities are stored and processed within the same fronto-temporal network that supports lexical and syntactic processes.

The role of systematicity in early referent selection

Previous studies showed that word learning is affected by children's existing knowledge. For instance, knowledge of semantic category aids word learning, whereas a dense phonological neighbourhood impedes learning of similar-sounding words. Here, we examined to what extent children associate similar-sounding words (e.g., rat and cat) with objects of the same semantic category (e.g., both are animals), that is, to what extent children assume meaning overlap given form overlap between two words. We tested this by first presenting children (N = 93, Mage = 22.4 months) with novel word-object associations. Then, we examined the extent to which children assume that a similar sounding novel label, that is, a phonological neighbour, refers to a similar looking object, that is, a likely semantic neighbour, as opposed to a dissimilar looking object. Were children to preferentially fixate the similar-looking novel object, it would suggest that systematic word form-meaning relations aid referent selection in young children. While we did not find any evidence for such word form-meaning systematicity, we demonstrated that children showed robust learning for the trained novel word-object associations, and were able to discriminate between similar-sounding labels and also similar-looking objects. Thus, we argue that unlike iconicity which appears early in vocabulary development, we find no evidence for systematicity in early referent selection.

Iconicity ratings for 14,000+ English words

Iconic words and signs are characterized by a perceived resemblance between aspects of their form and aspects of their meaning. For example, in English, iconic words include peep and crash, which mimic the sounds they denote, and wiggle and zigzag, which mimic motion. As a semiotic property of words and signs, iconicity has been demonstrated to play a role in word learning, language processing, and language evolution. This paper presents the results of a large-scale norming study for more than 14,000 English words conducted with over 1400 American English speakers. We demonstrate the utility of these ratings by replicating a number of existing findings showing that iconicity ratings are related to age of acquisition, sensory modality, semantic neighborhood density, structural markedness, and playfulness. We discuss possible use cases and limitations of the rating dataset, which is made publicly available.

On the Connection Between Language Change and Language Processing

Previous studies provided evidence for a connection between language processing and language change. We add to these studies with an exploration of the influence of lexical-distributional properties of words in orthographic space, semantic space, and the mapping between orthographic and semantic space on the probability of lexical extinction. Through a binomial linear regression analysis, we investigated the probability of lexical extinction by the first decade of the twenty-first century (2000s) for words that existed in the first decade of the nineteenth-century (1800s) in eight data sets for five languages: English, French, German, Italian, and Spanish. The binomial linear regression analysis revealed that words that are more similar in form to other words are less likely to disappear from a language. By contrast, words that are more similar in meaning to other words are more likely to become extinct. In addition, a more consistent mapping between form and meaning protects a word from lexical extinction. A nonlinear time-to-event analysis furthermore revealed that the position of a word in orthographic and semantic space continues to influence the probability of it disappearing from a language for at least 200 years. Effects of the lexical-distributional properties of words under investigation here have been reported in the language processing literature as well. The results reported here, therefore, fit well with a usage-based approach to language change, which holds that language change is at least to some extent connected to cognitive mechanisms in the human brain.

On the semiotic and material constraints of ideographies

Despite obvious advantages, no generalised ideographic codes have evolved through cultural evolution to rely on iconicity. Morin suggests that this is because of missing means of standardisation, which glottographic codes get from natural languages. Although we agree, we also point to the important role of the available media, which might support some forms of reference more effectively than others.

Puzzling out graphic codes

This response takes advantage of the diverse and wide-ranging series of commentaries to clarify some aspects of the target article, and flesh out other aspects. My central point is a plea to take graphic codes seriously as codes, rather than as a kind of visual art or as a byproduct of spoken language; only in this way can the puzzle of ideography be identified and solved. In this perspective, I argue that graphic codes do not derive their expressive power from iconicity alone (unlike visual arts), and I clarify the peculiar relationship that ties writing to spoken language. I then discuss three possible solutions to the puzzle of ideography. I argue that a learning account still cannot explain why ideographies fail to evolve, even if we emancipate the learning account from the version that Liberman put forward; I develop my preferred solution, the "standardization account," and contrast it with a third solution suggested by some commentaries, which says that ideographies do not evolve because they would make communication too costly. I consider, by way of conclusion, the consequences of these views for the future evolution of ideography.

The Iconicity Ring Hypothesis Bridges the Gap Between Symbol Grounding and Linguistic Relativity

Kemmerer captured the drastic change in theories of word meaning representations, contrasting the view that word meaning representations are amodal and universal, with the view that they are grounded and language-specific. However, he does not address how language can be simultaneously grounded and language-specific. Here, we approach this question from the perspective of language acquisition and evolution. We argue that adding a new element-iconicity-is critically beneficial and offer the iconicity ring hypothesis, which explains how language-specific, secondary iconicity might emerge from biologically grounded and universally shared iconicity in the course of language acquisition and evolution.

The (Co)Evolution of Language and Music Under Human Self-Domestication

Together with language, music is perhaps the most distinctive behavioral trait of the human species. Different hypotheses have been proposed to explain why only humans perform music and how this ability might have evolved in our species. In this paper, we advance a new model of music evolution that builds on the self-domestication view of human evolution, according to which the human phenotype is, at least in part, the outcome of a process similar to domestication in other mammals, triggered by the reduction in reactive aggression responses to environmental changes. We specifically argue that self-domestication can account for some of the cognitive changes, and particularly for the behaviors conducive to the complexification of music through a cultural mechanism. We hypothesize four stages in the evolution of music under self-domestication forces: (1) collective protomusic; (2) private, timbre-oriented music; (3) small-group, pitch-oriented music; and (4) collective, tonally organized music. This line of development encompasses the worldwide diversity of music types and genres and parallels what has been hypothesized for languages. Overall, music diversity might have emerged in a gradual fashion under the effects of the enhanced cultural niche construction as shaped by the progressive decrease in reactive (i.e., impulsive, triggered by fear or anger) aggression and the increase in proactive (i.e., premeditated, goal-directed) aggression.

The sound of swearing: Are there universal patterns in profanity?

Why do swear words sound the way they do? Swear words are often thought to have sounds that render them especially fit for purpose, facilitating the expression of emotion and attitude. To date, however, there has been no systematic cross-linguistic investigation of phonetic patterns in profanity. In an initial, pilot study we explored statistical regularities in the sounds of swear words across a range of typologically distant languages. The best candidate for a cross-linguistic phonemic pattern in profanity was the absence of approximants (sonorous sounds like l, r, w and y). In Study 1, native speakers of various languages (Arabic, Chinese, Finnish, French, German, Spanish; N = 215) judged foreign words less likely to be swear words if they contained an approximant. In Study 2 we found that sanitized versions of English swear words – like darn instead of damn – contain significantly more approximants than the original swear words. Our findings reveal that not all sounds are equally suitable for profanity, and demonstrate that sound symbolism – wherein certain sounds are intrinsically associated with certain meanings – is more pervasive than has previously been appreciated, extending beyond denoting single concepts to serving pragmatic functions.

Optionality in animal communication: a novel framework for examining the evolution of arbitrariness

A critical feature of language is that the form of words need not bear any perceptual similarity to their function - these relationships can be 'arbitrary'. The capacity to process these arbitrary form-function associations facilitates the enormous expressive power of language. However, the evolutionary roots of our capacity for arbitrariness, i.e. the extent to which related abilities may be shared with animals, is largely unexamined. We argue this is due to the challenges of applying such an intrinsically linguistic concept to animal communication, and address this by proposing a novel conceptual framework highlighting a key underpinning of linguistic arbitrariness, which is nevertheless applicable to non-human species. Specifically, we focus on the capacity to associate alternative functions with a signal, or alternative signals with a function, a feature we refer to as optionality. We apply this framework to a broad survey of findings from animal communication studies and identify five key dimensions of communicative optionality: signal production, signal adjustment, signal usage, signal combinatoriality and signal perception. We find that optionality is widespread in non-human animals across each of these dimensions, although only humans demonstrate it in all five. Finally, we discuss the relevance of optionality to behavioural and cognitive domains outside of communication. This investigation provides a powerful new conceptual framework for the cross-species investigation of the origins of arbitrariness, and promises to generate original insights into animal communication and language evolution more generally.

Are ape gestures like words? Outstanding issues in detecting similarities and differences between human language and ape gesture

Opinion piece: ape gestures are made intentionally, inviting parallels with human language; but how similar are their gestures to words? Here we ask this in three ways, considering: flexibility and ambiguity, first- and second-order intentionality, and usage in interactive exchanges. Many gestures are used to achieve several, often very distinct, goals. Such apparent ambiguity in meaning is potentially disruptive for communication, but-as with human language-situational and interpersonal context may largely resolve the intended meaning. Our evidence for first-order intentional use of gesture is abundant, but how might we establish a case for the second-order intentional use critical to language? Finally, words are rarely used in tidy signal-response sequences but are exchanged in back-and-forth interaction. Do gestures share this property? In this paper, we examine these questions and set out ways in which they can be resolved, incorporating data from wild chimpanzees. This article is part of the theme issue 'Cognition, communication and social bonds in primates'.

Not just form, not just meaning: Words with consistent form-meaning mappings are learned earlier

By leveraging Phonology-to-Semantics Consistency (PSC), which quantifies form-meaning systematicity as the semantic similarity between a target word and its phonological nearest neighbours, we document a unique effect of systematicity on Age of Acquisition (AoA). This effect is also found after controlling for the effect of neighbourhood density measured for word forms and lexical semantics and several other standard predictors of AoA. Moreover, we show that the effect of systematicity is not reducible to iconicity. Finally, we extensively probe the reliability of this finding by testing different statistical models, analysing systematicity in phonology and orthography and implementing random baselines, reporting a robust, unique negative effect of systematicity on AoA, such that more systematic words tend to be learned earlier. We discuss the findings in the light of studies on non-arbitrary form-meaning mappings and their role in language learning, focusing on the analogical process at the interface of form and meaning upon which PSC is based and how it could help children infer the semantics of novel words when context is scarce or uninformative, ultimately speeding up word learning.

Predicting the Structure of a Lexical Environment from Properties of Verbal Working Memory

We analyzed a Japanese lexical database to investigate the structure of the lexical environment based on the hypothesis that the lexical environment is optimized for the functioning of verbal working memory. Our prediction was that, as a consequence of the cultural transmission of language, low-imageable meanings tend to be represented by frequent phonological patterns in the current vocabulary rather than infrequent phonological patterns. This prediction was based on two findings of previous laboratory studies on verbal working memory. (1) The quality of phonological (phonemic and accent) representations in verbal working memory depends on phonological regularity knowledge; therefore, short-term phonological representations are less robust for words with infrequent phonological patterns. (2) Phonological representations are underpinned by contributions from semantic knowledge; therefore, phonological representations of highly imageable words are more robust than those for low-imageable words. Our database analyses show that nouns with less imageable meanings tend to be associated with more frequent phonological patterns in Japanese vocabulary. This lexical structure can maintain the quality of phonological representations in verbal working memory through contributions of semantic and phonological regularity knowledge. Larger semantic contributions compensate for the less robust phonological representations of infrequent phonological forms. The quality of phonological representations is preserved by phonological regularity knowledge when larger semantic contributions are not expected.

From woof woof to dog: Interactions between parents' use of sound symbolic words and infants' vocabulary development

Sound symbols, such as "woof woof" for a dog's barking, imitate the physical properties of their referents. Turkish is a sound symbolically rich language that allows flexible use of such words in different linguistic forms. The current study examined Turkish-speaking parents' use of sound symbolic words to their 14- and 20-month-olds and the concurrent and longitudinal relations between parents' sound symbolic input and infants' vocabulary knowledge. Thirty-four (n = 34) infants were observed at Time-1 (M_age  = 14.23 months, SD = 1.11) and Time-2 (M_age  = 20.30 months, SD = 1.24) during free play sessions with their parents to examine parental input. Infants' vocabulary knowledge was assessed by a parental report. Both the quantity and quality of parental sound symbolic input changed between 14 and 20 months of age. Furthermore, infants' earlier vocabulary knowledge at 14 months negatively predicted parents' later sound symbolic input at 20 months. Last, parents' sound symbolic input was positively and concurrently associated with 14-month-olds' vocabulary knowledge but was negatively and concurrently associated with 20-month-olds' vocabulary levels. These findings suggest an early interaction between infants' exposure to sound symbolic input and their vocabulary development.

Systematicity in language and the fast and slow creation of writing systems: Understanding two types of non-arbitrary relations between orthographic characters and their canonical pronunciation

Words that sound similar tend to have similar meanings, at a distributed, sub-symbolic level (Monaghan, Shillcock, Christiansen, & Kirby, 2014). We extend this paradigm for measuring systematicity to letters and their canonical pronunciations. We confirm that orthographies that were consciously constructed to be systematic (Korean and two shorthand writing systems) yield significant correlations between visual distances between characters and the corresponding phonological distances between canonical pronunciations. We then extend the approach to Arabic, Hebrew, and English and show that letters that look similar tend to sound similar in their canonical pronunciations. We indicate some of the implications for education, and for understanding typical and atypical reading. By using different visual distance metrics we distinguish between symbol-based (Korean, shorthand) and effort-based (Arabic, Hebrew, English) grapho-phonemic systematicity. We reinterpret existing demonstrations of phono-semantic systematicity in terms of cognitive effort.

Semantics of European poetry is shaped by conservative forces: The relationship between poetic meter and meaning in accentual-syllabic verse

Recent advances in cultural analytics and large-scale computational studies of art, literature and film often show that long-term change in the features of artistic works happens gradually. These findings suggest that conservative forces that shape creative domains might be underestimated. To this end, we provide the first large-scale formal evidence of the association between poetic meter and semantics in 18-19th century European literatures, using Czech, German and Russian collections with additional data from English poetry and early modern Dutch songs. Our study traces this association through a series of unsupervised classifications using the abstracted semantic features of poems that are inferred for individual texts with the aid of topic modeling. Topics alone enable recognition of the meters in each observed language, as may be seen from the same-meter samples clustering together (median Adjusted Rand Index between 0.48 and 1 across traditions). In addition, this study shows that the strength of the association between form and meaning tends to decrease over time. This may reflect a shift in aesthetic conventions between the 18th and 19th centuries as individual innovation was increasingly favored in literature. Despite this decline, it remains possible to recognize semantics of the meters from past or future, which suggests the continuity in meter-meaning relationships while also revealing the historical variability of conditions across languages. This paper argues that distinct metrical forms, which are often copied in a language over centuries, also maintain long-term semantic inertia in poetry. Our findings highlight the role of the formal features of cultural items in influencing the pace and shape of cultural evolution.

Grammatical Gender Disambiguates Syntactically Similar Nouns

Recent research into grammatical gender from the perspective of information theory has shown how seemingly arbitrary gender systems can ease processing demands by guiding lexical prediction. When the gender of a noun is revealed in a preceding element, the list of possible candidates is reduced to the nouns assigned to that gender. This strategy can be particularly effective if it eliminates words that are likely to compete for activation against the intended word. We propose syntax as the crucial context within which words must be disambiguated, hypothesizing that syntactically similar words should be less likely to share a gender cross-linguistically. We draw on recent work on syntactic information in the lexicon to define the syntactic distribution of a word as a probability vector of its participation in various dependency relations, and we extract such relations for 32 languages from the Universal Dependencies Treebanks. Correlational and mixed-effects regression analyses reveal that syntactically similar nouns are less likely to share a gender, the opposite pattern that is found for semantically and orthographically similar words. We interpret this finding as a design feature of language, and this study adds to a growing body of research attesting to the ways in which functional pressures on learning, memory, production, and perception shape the lexicon in different ways.

Identifying the Correlations Between the Semantics and the Phonology of American Sign Language and British Sign Language: A Vector Space Approach

Over the history of research on sign languages, much scholarship has highlighted the pervasive presence of signs whose forms relate to their meaning in a non-arbitrary way. The presence of these forms suggests that sign language vocabularies are shaped, at least in part, by a pressure toward maintaining a link between form and meaning in wordforms. We use a vector space approach to test the ways this pressure might shape sign language vocabularies, examining how non-arbitrary forms are distributed within the lexicons of two unrelated sign languages. Vector space models situate the representations of words in a multi-dimensional space where the distance between words indexes their relatedness in meaning. Using phonological information from the vocabularies of American Sign Language (ASL) and British Sign Language (BSL), we tested whether increased similarity between the semantic representations of signs corresponds to increased phonological similarity. The results of the computational analysis showed a significant positive relationship between phonological form and semantic meaning for both sign languages, which was strongest when the sign language lexicons were organized into clusters of semantically related signs. The analysis also revealed variation in the strength of patterns across the form-meaning relationships seen between phonological parameters within each sign language, as well as between the two languages. This shows that while the connection between form and meaning is not entirely language specific, there are cross-linguistic differences in how these mappings are realized for signs in each language, suggesting that arbitrariness as well as cognitive or cultural influences may play a role in how these patterns are realized. The results of this analysis not only contribute to our understanding of the distribution of non-arbitrariness in sign language lexicons, but also demonstrate a new way that computational modeling can be harnessed in lexicon-wide investigations of sign languages.

An investigation of iconic language development in four datasets

Iconic words imitate their meanings. Previous work has demonstrated that iconic words are more common in infants' early speech, and in adults' child-directed speech (e.g., Perry et al., 2015; 2018). This is consistent with the proposal that iconicity provides a benefit to word learning. Here we explored iconicity in four diverse language development datasets: a production corpus for infants and preschoolers (MacWhinney, 2000), comprehension data for school-aged children to young adults (Dale & O'Rourke, 1981), word frequency norms from educational texts for school aged children to young adults (Zeno et al., 1995), and a database of parent-reported infant word production (Frank et al., 2017). In all four analyses, we found that iconic words were more common at younger ages. We also explored how this relationship differed by syntactic class, finding only modest evidence for differences. Overall, the results suggest that, beyond infancy, iconicity is an important factor in language acquisition.

New neighbours make bad fences: Form-based semantic shifts in word learning

The meanings of words sometimes shift towards those of similar-sounding words. For example, expunge is etymologically related to puncture but now connotes "wiping away," and according to the Oxford English Dictionary, this shift "is probably influenced by phonetic association with sponge." However, evidence for such form-based semantic shifts is anecdotal. We therefore conducted two experiments where participants learned novel words in sentence contexts (e.g., The boss embraiched the team's proposal, so they had to start over) and applied the inferred meanings to ambiguous sentences by providing ratings on a 7-point scale (e.g., Carol embraiched Gerald. How pleased was Gerald?). The inferred meanings of novel words that are spelt like existing words (e.g., embraich, like embrace) shifted towards the meanings of those existing words, relative to control novel words learned in identical contexts (e.g., fline; participants rated Gerald as more pleased to be embraiched than to be flined). These experiments provide the first evidence that newly learned words can indeed undergo form-based semantic shifts. We propose that shifts like these occur during word learning, when words activate rather than inhibit similar-sounding words, and we discuss why they seem to be more common in low-frequency words.

"Big" Sounds Bigger in More Widely Spoken Languages

Larger communities face more communication barriers. We propose that languages spoken by larger communities adapt and overcome these greater barriers by increasing their reliance on sound symbolism, as sound symbolism can facilitate communication. To test whether widely spoken languages are more sound symbolic, participants listened to recordings of the words big and small in widely spoken and less common languages and guessed their meanings. Accuracy was higher for words from widely spoken languages providing evidence that widely spoken languages harbor more sound symbolism. Preliminary results also suggest that widely spoken languages rely on different sound symbolic patterns than less common languages. Community size can thus shape linguistic forms and influence the tools that languages use to facilitate communication.

When dogs meow: An electrophysiological study of lexical-semantic processing in toddlers

The goal of this study was to investigate lexical-semantic processing at an early phase of language development. Adults often communicate with children using infant-directed speech that typically involves lexical and syntactic modifications such as onomatopoeias (Soderstrom, 2007). Here, we asked how and when children start to show an advantage for processing conventional linguistic forms, such as common nouns, and consequently decreasing sensitivity to onomatopoeias. We recorded event-related brain potentials in children of two age groups (16-21 months and 24-31 months) and in an adult control group during the presentation of four conditions in which either common nouns or onomatopoeias were presented auditorily followed by a picture of an either congruent or incongruent object. We focused on the N400 effect, a more negative ERP response to incongruent compared with congruent semantic relations. The younger children showed an N400 effect only for onomatopoeic words, while the older children showed an N400 effect only for common nouns. The adults showed N400 effects for onomatopoeia and nouns. These different N400 effects suggest that onomatopoeia and common nouns are differently organized in children's semantic memory and that the acquisition of linguistic abilities affects and modifies semantic processing of different lexical information.

A Cross-Sectional Test of Sign Creation by Children in the Gesture and Vocal Modalities

Naturalistic studies show that children can create language-like communication systems in the absence of conventional language. However, experimental evidence is mixed. We address this discrepancy using an experimental paradigm that simulates naturalistic sign creation. Specifically, we tested if a sample of 6- to 12-year-old children (52 girls and 56 boys drawn from an urban, predominantly white population in Western Australia) can comprehend and create novel gestural and vocal signs. Experiment 1 tested children's ability to comprehend novel signs. Experiment 2 tested children's ability to create novel signs. Results show that children can comprehend and create gestural and vocal signs, that communication is more successful in the gesture modality, and that older children outperform younger children.

Correlations Between Handshape and Movement in Sign Languages

Sign language phonological parameters are somewhat analogous to phonemes in spoken language. Unlike phonemes, however, there is little linguistic literature arguing that these parameters interact at the sublexical level. This situation raises the question of whether such interaction in spoken language phonology is an artifact of the modality or whether sign language phonology has not been approached in a way that allows one to recognize sublexical parameter interaction. We present three studies in favor of the latter alternative: a shape-drawing study with deaf signers from six countries, an online dictionary study of American Sign Language, and a study of selected lexical items across 34 sign languages. These studies show that, once iconicity is considered, handshape and movement parameters interact at the sublexical level. Thus, consideration of iconicity makes transparent similarities in grammar across both modalities, allowing us to maintain certain key findings of phonological theory as evidence of cognitive architecture.

Iconicity and Diachronic Language Change

Iconicity, the resemblance between the form of a word and its meaning, has effects on behavior in both communicative symbol development and language learning experiments. These results have invited speculation about iconicity being a key feature of the origins of language, yet the presence of iconicity in natural languages seems limited. In a diachronic study of language change, we investigated the extent to which iconicity is a stable property of vocabulary, alongside previously investigated psycholinguistic predictors of change. Analyzing 784 English words with data on their historical forms, we found that stable words are higher in iconicity, longer in length, and earlier acquired during development, but that the role of frequency and grammatical category may be less important than previously suggested. Iconicity is revealed as a feature of ultra-conserved words and potentially also as a property of vocabulary early in the history of language origins.

The ASL-LEX 2.0 Project: A Database of Lexical and Phonological Properties for 2,723 Signs in American Sign Language

ASL-LEX is a publicly available, large-scale lexical database for American Sign Language (ASL). We report on the expanded database (ASL-LEX 2.0) that contains 2,723 ASL signs. For each sign, ASL-LEX now includes a more detailed phonological description, phonological density and complexity measures, frequency ratings (from deaf signers), iconicity ratings (from hearing non-signers and deaf signers), transparency ("guessability") ratings (from non-signers), sign and videoclip durations, lexical class, and more. We document the steps used to create ASL-LEX 2.0 and describe the distributional characteristics for sign properties across the lexicon and examine the relationships among lexical and phonological properties of signs. Correlation analyses revealed that frequent signs were less iconic and phonologically simpler than infrequent signs and iconic signs tended to be phonologically simpler than less iconic signs. The complete ASL-LEX dataset and supplementary materials are available at https://osf.io/zpha4/ and an interactive visualization of the entire lexicon can be accessed on the ASL-LEX page: http://asl-lex.org/.

Iconicity in Word Learning and Beyond: A Critical Review

Interest in iconicity (the resemblance-based mapping between aspects of form and meaning) is in the midst of a resurgence, and a prominent focus in the field has been the possible role of iconicity in language learning. Here we critically review theory and empirical findings in this domain. We distinguish local learning enhancement (where the iconicity of certain lexical items influences the learning of those items) and general learning enhancement (where the iconicity of certain lexical items influences the later learning of non-iconic items or systems). We find that evidence for local learning enhancement is quite strong, though not as clear cut as it is often described and based on a limited sample of languages. Despite common claims about broader facilitatory effects of iconicity on learning, we find that current evidence for general learning enhancement is lacking. We suggest a number of productive avenues for future research and specify what types of evidence would be required to show a role for iconicity in general learning enhancement. We also review evidence for functions of iconicity beyond word learning: iconicity enhances comprehension by providing complementary representations, supports communication about sensory imagery, and expresses affective meanings. Even if learning benefits may be modest or cross-linguistically varied, on balance, iconicity emerges as a vital aspect of language.

Sound Predicts Meaning: Cross-Modal Associations Between Formant Frequency and Emotional Tone in Stanzas

Research on the relation between sound and meaning in language has reported substantial evidence for implicit associations between articulatory-acoustic characteristics of phonemes and emotions. In the present study, we specifically tested the relation between the acoustic properties of a text and its emotional tone as perceived by readers. To this end, we asked participants to assess the emotional tone of single stanzas extracted from a large variety of poems. The selected stanzas had either an extremely high, a neutral, or an extremely low average formant dispersion. To assess the average formant dispersion per stanza, all words were phonetically transcribed and the distance between the first and second formant per vowel was calculated. Building on a long tradition of research on associations between sound frequency on the one hand and non-acoustic concepts such as size, strength, or happiness on the other hand, we hypothesized that stanzas with an extremely high average formant dispersion would be rated lower on items referring to Potency (dominance) and higher on items referring to Activity (arousal) and Evaluation (emotional valence). The results confirmed our hypotheses for the dimensions of Potency and Evaluation, but not for the dimension of Activity. We conclude that, at least in poetic language, extreme values of acoustic features of vowels are a significant predictor for the emotional tone of a text.

Of mice and men: Speech sound acquisition as discriminative learning from prediction error, not just statistical tracking

Despite burgeoning evidence that listeners are highly sensitive to statistical distributions of speech cues, the mechanism underlying learning may not be purely statistical tracking. Decades of research in animal learning suggest that learning results from prediction and prediction error. Two artificial language learning experiments test two predictions that distinguish error-driven from purely statistical models; namely, cue competition - specifically, Kamin's (1968) 'blocking' effect (Experiment 1) - and the predictive structure of learning events (Experiment 2). In Experiment 1, prior knowledge of an informative cue blocked learning of a second cue. This finding may help explain second language learners' difficulty in acquiring native-level perception of non-native speech cues. In Experiment 2, learning was better with a discriminative (cue-outcome) order compared to a non-discriminative (outcome-cue) order. Experiment 2 suggests that learning speech cues, including reversing effects of blocking, depends on (un)learning from prediction error and depends on the temporal order of auditory cues versus semantic outcomes. Together, these results show that (a) existing knowledge of acoustic cues can block later learning of new cues, and (b) speech sound acquisition depends on the predictive structure of learning events. When feedback from prediction error is available, this drives learners to ignore salient non-discriminative cues and effectively learn to use target cue dimensions. These findings may have considerable implications for the field of speech acquisition.

How optimal is word recognition under multimodal uncertainty?

Identifying a spoken word in a referential context requires both the ability to integrate multimodal input and the ability to reason under uncertainty. How do these tasks interact with one another? We study how adults identify novel words under joint uncertainty in the auditory and visual modalities, and we propose an ideal observer model of how cues in these modalities are combined optimally. Model predictions are tested in four experiments where recognition is made under various sources of uncertainty. We found that participants use both auditory and visual cues to recognize novel words. When the signal is not distorted with environmental noise, participants weight the auditory and visual cues optimally, that is, according to the relative reliability of each modality. In contrast, when one modality has noise added to it, human perceivers systematically prefer the unperturbed modality to a greater extent than the optimal model does. This work extends the literature on perceptual cue combination to the case of word recognition in a referential context. In addition, this context offers a link to the study of multimodal information in word meaning learning.

Mother Schema, Obstetric Dilemma, and the Origin of Behavioral Modernity

What triggered the emergence of uniquely human behaviors (language, religion, music) some 100,000 years ago? A non-circular, speculative theory based on the mother-infant relationship is presented. Infant "cuteness" evokes the infant schema and motivates nurturing; the analogous mother schema (MS) is a multimodal representation of the carer from the fetal/infant perspective, motivating fearless trust. Prenatal MS organizes auditory, proprioceptive, and biochemical stimuli (voice, heartbeat, footsteps, digestion, body movements, biochemicals) that depend on maternal physical/emotional state. In human evolution, bipedalism and encephalization led to earlier births and more fragile infants. Cognitively more advanced infants survived by better communicating with and motivating (manipulating) mothers and carers. The ability to link arbitrary sound patterns to complex meanings improved (proto-language). Later in life, MS and associated emotions were triggered in ritual settings by repetitive sounds and movements (early song, chant, rhythm, dance), subdued light, dull auditory timbre, psychoactive substances, unusual tastes/smells and postures, and/or a feeling of enclosure. Operant conditioning can explain why such actions were repeated. Reflective consciousness emerged as infant-mother dyads playfully explored intentionality (theory of mind, agent detection) and carers predicted and prevented fatal infant accidents (mental time travel). The theory is consistent with cross-cultural commonalities in altered states (out-of-body, possessing, floating, fusing), spiritual beings (large, moving, powerful, emotional, wise, loving), and reports of strong musical experiences and divine encounters. Evidence is circumstantial and cumulative; falsification is problematic.

How alliteration enhances conceptual-attentional interactions in reading

In linguistics, the relationship between phonological word form and meaning is mostly considered arbitrary. Why, then, do literary authors traditionally craft sound relationships between words? We set out to characterise how dynamic interactions between word form and meaning may account for this literary practice. Here, we show that alliteration influences both meaning integration and attentional engagement during reading. We presented participants with adjective-noun phrases, having manipulated semantic relatedness (congruent, incongruent) and form repetition (alliterating, non-alliterating) orthogonally, as in "dazzling-diamond"; "sparkling-diamond"; "dangerous-diamond"; and "creepy-diamond". Using simultaneous recording of event-related brain potentials and pupil dilation (PD), we establish that, whilst semantic incongruency increased N400 amplitude as expected, it reduced PD, an index of attentional engagement. Second, alliteration affected semantic evaluation of word pairs, since it reduced N400 amplitude even in the case of unrelated items (e.g., "dangerous-diamond"). Third, alliteration specifically boosted attentional engagement for related words (e.g., "dazzling-diamond"), as shown by a sustained negative correlation between N400 amplitudes and PD change after the window of lexical integration. Thus, alliteration strategically arouses attention during reading and when comprehension is challenged, phonological information helps readers link concepts beyond the level of literal semantics. Overall, our findings provide a tentative mechanism for the empowering effect of sound repetition in literary constructs.

What Does a Horgous Look Like? Nonsense Words Elicit Meaningful Drawings

To what extent do people attribute meanings to "nonsense" words? How general is such attribution of meaning? We used a set of words lacking conventional meanings to elicit drawings of made-up creatures. Separate groups of participants rated the nonsense words and the drawings on several semantic dimensions and selected what name best corresponded to each creature. Despite lacking conventional meanings, "nonsense" words elicited a high level of consistency in the produced drawings. Meaning attributions made to nonsense words corresponded with meaning attributions made by separate people to drawings that were inspired by the name. Naïve participants were able to recover the name that inspired the drawing with greater-than-chance accuracy. These results suggest that people make liberal and consistent use of non-arbitrary relationships between forms and meanings. OPEN RESEARCH BADGES: This article has been awarded Open Materials and Open Data badges. All materials and data are publicly accessible via the Open Science Framework at https://osf.io/8juyc/. Learn more about the Open Practices badges from the Center for Open Science: https://osf.io/tvyxz/wiki.

A Protracted Sensitive Period Regulates the Development of Cross-Modal Sound-Shape Associations in Humans

Humans preferentially match arbitrary words containing higher- and lower-frequency phonemes to angular and smooth shapes, respectively. Here, we investigated the role of visual experience in the development of audiovisual and audiohaptic sound-shape associations (SSAs) using a unique set of five groups: individuals who had suffered a transient period of congenital blindness through congenital bilateral dense cataracts before undergoing cataract-reversal surgeries (CC group), individuals with a history of developmental cataracts (DC group), individuals with congenital permanent blindness (CB group), individuals with late permanent blindness (LB group), and controls with typical sight (TS group). Whereas the TS and LB groups showed highly robust SSAs, the CB, CC, and DC groups did not-in any of the modality combinations tested. These results provide evidence for a protracted sensitive period during which aberrant vision prevents SSA acquisition. Moreover, the finding of a systematic SSA in the LB group demonstrates that representations acquired during the sensitive period are resilient to loss despite dramatically changed experience.

Cross-linguistically shared and language-specific sound symbolism in novel words elicited by locomotion videos in Japanese and English

This paper demonstrates a new quantitative approach to examine cross-linguistically shared and language-specific sound symbolism in languages. Unlike most previous studies taking a hypothesis-testing approach, we employed a data mining approach to uncover unknown sound-symbolic correspondences in the domain of locomotion, without limiting ourselves to pre-determined sound-meaning correspondences. In the experiment, we presented 70 locomotion videos to Japanese and English speakers and asked them to create a sound symbolically matching word for each action. Participants also rated each action on five meaning variables. Multivariate analyses revealed cross-linguistically shared and language-specific sound-meaning correspondences within a single semantic domain. The present research also established that a substantial number of sound-symbolic links emerge from conventionalized form-meaning mappings in the native languages of the speakers.

A multi-sensory code for emotional arousal

People express emotion using their voice, face and movement, as well as through abstract forms as in art, architecture and music. The structure of these expressions often seems intuitively linked to its meaning: romantic poetry is written in flowery curlicues, while the logos of death metal bands use spiky script. Here, we show that these associations are universally understood because they are signalled using a multi-sensory code for emotional arousal. Specifically, variation in the central tendency of the frequency spectrum of a stimulus-its spectral centroid-is used by signal senders to express emotional arousal, and by signal receivers to make emotional arousal judgements. We show that this code is used across sounds, shapes, speech and human body movements, providing a strong multi-sensory signal that can be used to efficiently estimate an agent's level of emotional arousal.

Semantic Associations Dominate Over Perceptual Associations in Vowel-Size Iconicity

We tested the influence of perceptual features on semantic associations between the acoustic characteristics of vowels and the notion of size. To this end, we designed an experiment in which we manipulated size on two dissociable levels: the physical size of the pictures presented during the experiment (perceptual level) and the implied size of the objects depicted in the pictures (semantic level). Participants performed an Implicit Association Test in which the pictures of small objects were larger than those of large objects - that is, the actual size ratio on the semantic level was inverted on the perceptual level. Our results suggest that participants matched visual and acoustic stimuli in accordance with the content of the pictures (i.e., the inferred size of the depicted object), whereas directly perceivable features (i.e., the physical size of the picture) had only a marginal influence on participants' performance. Moreover, as the experiment has been conducted at two different sites (Japan and Germany), the results also suggest that the participants' cultural background or mother tongue had only a negligible influence on the effect. Our results, therefore, support the assumption that associations across sensory modalities can be motivated by the semantic interpretation of presemantic stimuli.

Contiguity-based sound iconicity: The meaning of words resonates with phonetic properties of their immediate verbal contexts

We tested the hypothesis that phonosemantic iconicity--i.e., a motivated resonance of sound and meaning--might not only be found on the level of individual words or entire texts, but also in word combinations such that the meaning of a target word is iconically expressed, or highlighted, in the phonetic properties of its immediate verbal context. To this end, we extracted single lines from German poems that all include a word designating high or low dominance, such as large or small, strong or weak, etc. Based on insights from previous studies, we expected to find more vowels with a relatively short distance between the first two formants (low formant dispersion) in the immediate context of words expressing high physical or social dominance than in the context of words expressing low dominance. Our findings support this hypothesis, suggesting that neighboring words can form iconic dyads in which the meaning of one word is sound-iconically reflected in the phonetic properties of adjacent words. The construct of a contiguity-based phono-semantic iconicity opens many venues for future research well beyond lines extracted from poems.

How Efficiency Shapes Human Language

Cognitive science applies diverse tools and perspectives to study human language. Recently, an exciting body of work has examined linguistic phenomena through the lens of efficiency in usage: what otherwise puzzling features of language find explanation in formal accounts of how language might be optimized for communication and learning? Here, we review studies that deploy formal tools from probability and information theory to understand how and why language works the way that it does, focusing on phenomena ranging from the lexicon through syntax. These studies show how a pervasive pressure for efficiency guides the forms of natural language and indicate that a rich future for language research lies in connecting linguistics to cognitive psychology and mathematical theories of communication and inference.