Publications

Abstract

Human social intelligence relies on our ability to infer other people’s mental states such as their beliefs, desires,and intentions. While people are proficient at mental state inference from physical action, it is unknown whether people can make inferences of comparable granularity from simple linguistic events. Here, we show that people can make quantitative mental state attributions from simple referential expressions, replicating the fine-grained inferential structure characteristic of nonlinguistic theory of mind. Moreover, people quantitatively adjust these inferences after brief exposures to speaker-specific speech patterns. These judgments matched the predictions made by our computational model of theory of mind in language, but could not be explained by a simpler qualitative model that attributes mental states deductively. Our findings show how the connection between language and theory of mind runs deep, with their interaction showing in one of the most fundamental forms of human communication: reference.

Abstract

We hypothesize that contrast perception works as a visual heuristic, such that when speakers perceive a significant degree of contrast in a visual context, they tend to produce the corresponding adjective to describe a referent. The contrast perception heuristic supports efficient audience design, allowing speakers to produce referential expressions with minimum expenditure of cognitive resources, while facilitating the listener's visual search for the referent. We tested the perceptual contrast hypothesis in three language-production experiments. Experiment 1 revealed that speakers overspecify color adjectives in polychrome displays, whereas in monochrome displays they overspecified other properties that were contrastive. Further support for the contrast perception hypothesis comes from a re-analysis of previous work, which confirmed that color contrast elicits color overspecification when detected in a given display, but not when detected across monochrome trials. Experiment 2 revealed that even atypical colors (which are often overspecified) are only mentioned if there is color contrast. In Experiment 3, participants named a target color faster in monochrome than in polychrome displays, suggesting that the effect of color contrast is not analogous to ease of production. We conclude that the tendency to overspecify color in polychrome displays is not a bottom-up effect driven by the visual salience of color as a property, but possibly a learned communicative strategy. We discuss the implications of our account for pragmatic theories of referential communication and models of audience design, challenging the view that overspecification is a form of egocentric behavior.

Abstract

Similes require two different pragmatic skills: appreciating the intended similarity and deriving a scalar implicature (e.g., “Lucy is like a parrot” normally implies that Lucy is not a parrot), but previous studies overlooked this second skill. In Experiment 1, preschoolers (N = 48; ages 3–5) understood “X is like a Y” as an expression of similarity. In Experiment 2 (N = 99; ages 3–6, 13) and Experiment 3 (N = 201; ages 3–5 and adults), participants received metaphors (“Lucy is a parrot”) or similes (“Lucy is like a parrot”) as clues to select one of three images (a parrot, a girl or a parrot-looking girl). An early developmental trend revealed that 3-year-olds started deriving the implicature “X is not a Y,” whereas 5-year-olds performed like adults.

Abstract

A psychophysical analysis of referential communication establishes a causal link between a visual stimulus and a speaker’s perception of this stimulus, and between the speaker’s internal representation and their reference production. Here, I argue that, in addition to visual perception and language, social cognition plays an integral part in this complex process, as it enables successful speaker-listener coordination. This pragmatic analysis of referential communication tries to explain the redundant use of color adjectives. It is well documented that people use color words when it is not necessary to identify the referent; for instance, they may refer to “the blue star” in a display of shapes with a single star. This type of redundancy challenges influential work from cognitive science and philosophy of language, suggesting that human communication is fundamentally efficient. Here, I explain these seemingly contradictory findings by confirming the visual efficiency hypothesis: redundant color words can facilitate the listener’s visual search for a referent, despite making the description unnecessarily long. Participants’ eye movements revealed that they were faster to find “the blue star” than “the star” in a display of shapes with only one star. A language production experiment further revealed that speakers are highly sensitive to a target’s discriminability, systematically reducing their use of redundant color adjectives as the color of the target became more pervasive in a display. It is concluded that a referential expression’s efficiency should be based not only on its informational value, but also on its discriminatory value, which means that redundant color words can be more efficient than shorter descriptions.

Abstract

Pragmatic theories and computational models of reference must account for people’s frequent use of redundant color adjectives (e.g., referring to a single triangle as “the blue triangle”). The standard pragmatic view holds that the informativity of a referential expression depends on pragmatic contrast: Color adjectives should be used to contrast competitors of the same kind to preempt an ambiguity (e.g., between several triangles of different colors), otherwise they are redundant. Here we propose an alternative to the standard view, the incremental efficiency hypothesis, according to which the efficiency of a referential expression must be calculated incrementally over the entire visual context. This is the first theoretical account of referential efficiency that is sensitive to the incrementality of language processing, making different cross-linguistic predictions depending on word order. Experiment 1 confirmed that English speakers produced more redundant color adjectives (e.g., “the blue triangle”) than Spanish speakers (e.g., “el triángulo azul”), but both language groups used more redundant color adjectives in denser displays where it would be more efficient. In Experiments 2A and 2B, we used eye tracking to show that pragmatic contrast is not a processing constraint. Instead, incrementality and efficiency determine that English listeners establish color contrast across categories (BLUE SHAPES > TRIANGULAR ONE), whereas Spanish listeners establish color contrast within a category (TRIANGLES > BLUE ONE). Spanish listeners, however, reversed their visual search strategy when tested in English immediately after. Our results show that speakers and listeners of different languages exploit word order to increase communicative efficiency.

Abstract

Language and Theory of Mind come together in communication, but their relationship has been intensely contested. I hypothesize that pragmatic markers connect language and Theory of Mind and enable their co-development and co-evolution through a positive feedback loop, whereby the development of one skill boosts the development of the other. I propose to test this hypothesis by investigating two types of pragmatic markers: demonstratives (e.g., ‘this’ vs. ‘that’ in English) and articles (e.g., ‘a’ vs. ‘the’). Pragmatic markers are closed-class words that encode non-representational information that is unavailable to consciousness, but accessed automatically in processing. These markers have been associated with implicit Theory of Mind because they are used to establish joint attention (e.g., ‘I prefer that one’) and mark shared knowledge (e.g., ‘We bought the house’ vs. ‘We bought a house’). Here I develop a theoretical account of how joint attention (as driven by the use of demonstratives) is the basis for children’s later tracking of common ground (as marked by definite articles). The developmental path from joint attention to common ground parallels language change, with demonstrative forms giving rise to definite articles. This parallel opens the possibility of modelling the emergence of Theory of Mind in human development in tandem with its routinization across language communities and generations of speakers. I therefore propose that, in order to understand the relationship between language and Theory of Mind, we should study pragmatics at three parallel timescales: during language acquisition, language use, and language change.