Reference Production as Search: The Impact of Domain Size on the Production of Distinguishing Descriptions

Realistic About Reference Production: Testing the Effects of Domain Size and Saturation

Experiments on visually grounded, definite reference production often manipulate simple visual scenes in the form of grids filled with objects, for example, to test how speakers are affected by the number of objects that are visible. Regarding the latter, it was found that speech onset times increase along with domain size, at least when speakers refer to nonsalient target objects that do not pop out of the visual domain. This finding suggests that even in the case of many distractors, speakers perform object-by-object scans of the visual scene. The current study investigates whether this systematic processing strategy can be explained by the simplified nature of the scenes that were used, and if different strategies can be identified for photo-realistic visual scenes. In doing so, we conducted a preregistered experiment that manipulated domain size and saturation; replicated the measures of speech onset times; and recorded eye movements to measure speakers' viewing strategies more directly. Using controlled photo-realistic scenes, we find (1) that speech onset times increase linearly as more distractors are present; (2) that larger domains elicit relatively fewer fixation switches back and forth between the target and its distractors, mainly before speech onset; and (3) that speakers fixate the target relatively less often in larger domains, mainly after speech onset. We conclude that careful object-by-object scans remain the dominant strategy in our photo-realistic scenes, to a limited extent combined with low-level saliency mechanisms. A relevant direction for future research would be to employ less controlled photo-realistic stimuli that do allow for interpretation based on context.

Linguistic Redundancy and its Effects on Younger and Older Adults' Real-Time Comprehension and Memory

Redundant modifiers can facilitate referential interpretation by narrowing attention to intended referents. This is intriguing because, on traditional accounts, redundancy should impair comprehension. Little is known, however, about the effects of redundancy on older adults' comprehension. Older adults may show different patterns due to age-related decline (e.g., processing speed and memory) or their greater proclivity for linguistic redundancy, as suggested in language production studies. The present study explores the effects of linguistic redundancy on younger and older listeners' incremental referential processing, judgments of informativity, and downstream memory performance. In an eye tracking task, gaze was monitored as listeners followed instructions from a social robot referring to a unique object within a multi-object display. Critical trials were varied in terms of modifier type ("…closed/purple/[NONE] umbrella") and whether displays contained another object matching target properties (closed purple notebook), making modifiers less effective at narrowing attention. Relative to unmodified descriptions, redundant color modifiers facilitated comprehension, particularly when they narrowed attention to a single referent. Descriptions with redundant state modifiers always impaired real-time comprehension. In contrast, memory measures showed faster recognition of objects previously described with redundant state modifiers. Although color and state descriptions had different effects on referential processing and memory, informativity judgments showed participants perceived them as informationally redundant to the same extent relative to unmodified descriptions. Importantly, the patterns did not differ by listener age. Together, the results show that the effects of linguistic redundancy are stable across adulthood but vary as a function of modifier type, visual context, and the measured phenomenon.

Rational Redundancy in Referring Expressions: Evidence from Event-related Potentials

In referential communication, Grice's Maxim of Quantity is thought to imply that utterances conveying unnecessary information should incur comprehension difficulties. There is, however, considerable evidence that speakers frequently encode redundant information in their referring expressions, raising the question as to whether such overspecifications hinder listeners' processing. Evidence from previous work is inconclusive, and mostly comes from offline studies. In this article, we present two event-related potential (ERP) experiments, investigating the real-time comprehension of referring expressions that contain redundant adjectives in complex visual contexts. Our findings provide support for both Gricean and bounded-rational accounts. We argue that these seemingly incompatible results can be reconciled if common ground is taken into account. We propose a bounded-rational account of overspecification, according to which even redundant words can be beneficial to comprehension to the extent that they facilitate the reduction of listeners' uncertainty regarding the target referent.

Contrast perception as a visual heuristic in the formulation of referential expressions

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.

Reevaluating pragmatic reasoning in language games

The results of a highly influential study that tested the predictions of the Rational Speech Act (RSA) model suggest that (a) listeners use pragmatic reasoning in one-shot web-based referential communication games despite the artificial, highly constrained, and minimally interactive nature of the task, and (b) that RSA accurately captures this behavior. In this work, we reevaluate the contribution of the pragmatic reasoning formalized by RSA in explaining listener behavior by comparing RSA to a baseline literal listener model that is only driven by literal word meaning and the prior probability of referring to an object. Across three experiments we observe only modest evidence of pragmatic behavior in one-shot web-based language games, and only under very limited circumstances. We find that although RSA provides a strong fit to listener responses, it does not perform better than the baseline literal listener model. Our results suggest that while participants playing the role of the Speaker are informative in these one-shot web-based reference games, participants playing the role of the Listener only rarely take this Speaker behavior into account to reason about the intended referent. In addition, we show that RSA's fit is primarily due to a combination of non-pragmatic factors, perhaps the most surprising of which is that in the majority of conditions that are amenable to pragmatic reasoning, RSA (accurately) predicts that listeners will behave non-pragmatically. This leads us to conclude that RSA's strong overall correlation with human behavior in one-shot web-based language games does not reflect listener's pragmatic reasoning about informative speakers.

When more is more: redundant modifiers can facilitate visual search

According to the Gricean Maxim of Quantity, speakers provide the amount of information listeners require to correctly interpret an utterance, and no more (Grice in Logic and conversation, 1975). However, speakers do tend to violate the Maxim of Quantity often, especially when the redundant information improves reference precision (Degen et al. in Psychol Rev 127(4):591-621, 2020). Redundant (non-contrastive) information may facilitate real-world search if it narrows the spatial scope under consideration, or improves target template specificity. The current study investigated whether non-contrastive modifiers that improve reference precision facilitate visual search in real-world scenes. In two visual search experiments, we compared search performance when perceptually relevant, but non-contrastive modifiers were included in the search instruction. Participants (NExp. 1 = 48, NExp. 2 = 48) searched for a unique target object following a search instruction that contained either no modifier, a location modifier (Experiment 1: on the top left, Experiment 2: on the shelf), or a color modifier (the black lamp). In Experiment 1 only, the target was located faster when the verbal instruction included either modifier, and there was an overall benefit of color modifiers in a combined analysis for scenes and conditions common to both experiments. The results suggest that violations of the Maxim of Quantity can facilitate search when the violations include task-relevant information that either augments the target template or constrains the search space, and when at least one modifier provides a highly reliable cue. Consistent with Degen et al. (2020), we conclude that listeners benefit from non-contrastive information that improves reference precision, and engage in rational reference comprehension. SIGNIFICANCE STATEMENT: This study investigated whether providing more information than someone needs to find an object in a photograph helps them to find that object more easily, even though it means they need to interpret a more complicated sentence. Before searching a scene, participants were either given information about where the object would be located in the scene, what color the object was, or were only told what object to search for. The results showed that providing additional information helped participants locate an object in an image more easily only when at least one piece of information communicated what part of the scene the object was in, which suggests that more information can be beneficial as long as that information is specific and helps the recipient achieve a goal. We conclude that people will pay attention to redundant information when it supports their task. In practice, our results suggest that instructions in other contexts (e.g., real-world navigation, using a smartphone app, prescription instructions, etc.) can benefit from the inclusion of what appears to be redundant information.

Adjective forms and functions in British English child-directed speech

Adjectives are essential for describing and differentiating concepts. However, they have a protracted development relative to other word classes. Here we measure three- and four-year-olds' exposure to adjectives across a range of interactive and socioeconomic contexts to: (i) measure the syntactic, semantic, and pragmatic variability of adjectives in child-directed speech (CDS); and (ii) investigate how features of the input might scaffold adjective acquisition. In our novel corpus of UK English, adjectives occurred more frequently in prenominal than in postnominal (predicative) syntactic frames, though postnominal frames were more frequent for less-familiar adjectives. They occurred much more frequently with a descriptive than a contrastive function, especially for less-familiar adjectives. Our findings present a partial mismatch between the forms of adjectives found in real-world CDS and those forms that have been shown to be more useful for learning. We discuss implications for models of adjective acquisition and for clinical practice.

Overinformative Speakers Are Cooperative: Revisiting the Gricean Maxim of Quantity

A pragmatic account of referential communication is developed which presents an alternative to traditional Gricean accounts by focusing on cooperativeness and efficiency, rather than informativity. The results of four language-production experiments support the view that speakers can be cooperative when producing redundant adjectives, doing so more often when color modification could facilitate the listener's search for the referent in the visual display (Experiment 1a). By contrast, when the listener knew which shape was the target, speakers did not produce redundant color adjectives (Experiment 1b). English speakers used redundant color adjectives more often than Spanish speakers, suggesting that speakers are sensitive to the differential efficiency of prenominal and postnominal modification (Experiment 2). Speakers were also cooperative when using redundant size adjectives (Experiment 3). Overall, these results show how discriminability affects a speaker's choice of referential expression above and beyond considerations of informativity, supporting the view that redundant speakers can be cooperative.

On Visually-Grounded Reference Production: Testing the Effects of Perceptual Grouping and 2D/3D Presentation Mode

When referring to a target object in a visual scene, speakers are assumed to consider certain distractor objects to be more relevant than others. The current research predicts that the way in which speakers come to a set of relevant distractors depends on how they perceive the distance between the objects in the scene. It reports on the results of two language production experiments, in which participants referred to target objects in photo-realistic visual scenes. Experiment 1 manipulated three factors that were expected to affect perceived distractor distance: two manipulations of perceptual grouping (region of space and type similarity), and one of presentation mode (2D vs. 3D). In line with most previous research on visually-grounded reference production, an offline measure of visual attention was taken here: the occurrence of overspecification with color. The results showed effects of region of space and type similarity on overspecification, suggesting that distractors that are perceived as being in the same group as the target are more often considered relevant distractors than distractors in a different group. Experiment 2 verified this suggestion with a direct measure of visual attention, eye tracking, and added a third manipulation of grouping: color similarity. For region of space in particular, the eye movements data indeed showed patterns in the expected direction: distractors within the same region as the target were fixated more often, and longer, than distractors in a different region. Color similarity was found to affect overspecification with color, but not gaze duration or the number of distractor fixations. Also the expected effects of presentation mode (2D vs. 3D) were not convincingly borne out by the data. Taken together, these results provide direct evidence for the close link between scene perception and language production, and indicate that perceptual grouping principles can guide speakers in determining the distractor set during reference production.

Rational over-specification in visually-situated comprehension and production

Contrary to the Gricean maxims of quantity (Grice, in: Cole, Morgan (eds) Syntax and semantics: speech acts, vol III, pp 41–58, Academic Press, New York, 1975), it has been repeatedly shown that speakers often include redundant information in their utterances (over-specifications). Previous research on referential communication has long debated whether this redundancy is the result of speaker-internal or addressee-oriented processes, while it is also unclear whether referential redundancy hinders or facilitates comprehension. We present an information-theoretic explanation for the use of over-specification in visually-situated communication, which quantifies the amount of uncertainty regarding the referent as entropy (Shannon in Bell Syst Tech J 5:10, 10.1002/j.1538-7305.1948.tb01338.x, 1948). Examining both the comprehension and production of over-specifications, we present evidence that (a) listeners’ processing is facilitated by the use of redundancy as well as by a greater reduction of uncertainty early on in the utterance, and (b) that at least for some speakers, listeners’ processing concerns influence their encoding of over-specifications: Speakers were more likely to use redundant adjectives when these adjectives reduced entropy to a higher degree than adjectives necessary for target identification.