Rational Redundancy in Situated Communication

Contrary to the Gricean maxims of Quantity (Grice, 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 a bounded-rational account of referential redundancy, according to which any word in an utterance, even if it is redundant, can be beneficial to comprehension, to the extent that it facilitates the reduction of listeners’ uncertainty regarding the target referent in a co-present visual scene. Information-theoretic metrics, such as Shannon’s entropy (Shannon, 1948), were employed in order to quantify this uncertainty in bits of information, and gain an estimate of the cognitive effort related to referential processing. Under this account, speakers may, therefore, utilise redundant adjectives in order to reduce the visually-determined entropy (and thereby their listeners’ cognitive effort) more uniformly across their utterances. In a series of experiments, we examined both the comprehension and the production of over-specifications in complex visual contexts. Our findings are in line with the bounded-rational account. Specifically, we present evidence that: (a) in view of complex visual scenes, listeners’ processing and identification of the target referent may be facilitated by the use of redundant adjectives, as well as by a more uniform reduction of uncertainty across the utterance, and (b) that, while both speaker-internal and addressee-oriented processes are at play in the production of over-specifications, listeners’ processing concerns may also influence the encoding of redundant adjectives, at least for some speakers, who encode redundant adjectives more frequently when these adjectives contribute to a more uniform reduction of referential entropy.SFB1102 Information Density and Linguistic Encoding (iDeaL

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

Do speakers adapt object descriptions to listeners under load?

For successful communication, it is important that speaker and listener have established a common ground (Clark, 1996). For example, a speaker saying ‘please give me the green chair’ needs to have made sure, among other things, that there is an object near the listener that can be uniquely identified by the referring expression ‘the green chair’. If the listener sees only one chair, mentioning ‘green’ is redundant; if the listener sees more than one green chair, the expression may be underspecified. There is a hot debate as to whether speakers consider the perspective of the listener when making linguistic choices. It is generally accepted that speakers adapt their language to addressees at least at a crude level (e.g. Galati & Brennan, 2010), but it is less clear which cues trigger speakers to explicitly consider the listener’s needs. In this study, we investigated whether speakers adapt descriptions of objects to addressees who are under an increased cognitive load. According to the Uniform Information Density hypothesis (UID; Levy & Jaeger, 2007), speakers strive to produce utterances that minimize peaks in information density, which may lead to processing difficulty for the listener. If speakers are sensitive to the processing capacity of their addressees, they should adjust the overall information density of their utterances to a level that they expect the addressee to be able to process. Hence, we hypothesized that, when the addressee is involved in a difficult task that is noticeably reducing their cognitive capacity, speakers will introduce more redundancy in their descriptions, thereby distributing information over more linguistic units. To test this hypothesis, we conducted a referential communication experiment with pairs of speakers and listeners in a driving simulator. The speaker was in the passenger’s seat and described pieces of furniture (cf. the TUNA corpus; Gatt, et al., 2007) for the listener, who was performing a driving task. Speakers were instructed to describe each object in such a way that the listener could identify it from a set of furniture objects appearing on the driving simulator screen. The objects could be identified by mentioning a particular set of properties (a minimal description) concerning its color, size and/or orientation. Any mentioned property that was not necessary to uniquely identify the referent was considered redundant (cf. Koolen et al., 2013). We manipulated the listener’s cognitive load by varying the difficulty of the driving task in two blocks. In the easy driving block, listeners had to drive down a straight road, while in the difficult driving block, they had to perform a challenging tracking task that has previously been shown to increase cognitive load (Demberg, et al., 2013). The order of the blocks was counterbalanced across participants. After completing the two blocks, speaker and listener switched roles and repeated the experiment with a new set of items. In this way, half of the participants had first-hand experience with the driving task before taking the speaker role. We predicted that speakers would lower the information density of their descriptions, using more redundant attributes and/or producing longer descriptions, when listeners perform a difficult as compared to an easy driving task. In addition, we predicted that adaptation effects would be stronger when speakers had already experienced the driving task before describing. The results showed that in the first block, speakers used more redundant attributes (but not otherwise longer descriptions) when it was a difficult driving block than when it was an easy driving block, but only when the speaker had already been the driver in the first half of the experiment (cumulative link mixed model analysis, β = 0.9368; SE = 0.4497; p < .05). This finding is in line with the view that speakers only take the listener’s perspective into account when there are strong cues that adaptation is necessary (e.g. Pickering & Garrod, 2004). In addition, speakers did not seem to adjust their level of redundancy between the first and the second block, even though the second block had the other driving condition (see Figure 1). This suggests that speakers adapt to their first assessment of listeners' cognitive load, but not when cognitive load changes halfway through the task

How speakers adapt object descriptions to listeners under load

A controversial issue in psycholinguistics is the degree to which speakers employ audience design during language production. Hypothesising that a consideration of the listener’s needs is particularly relevant when the listener is under cognitive load, we had speakers describe objects for a listener performing an easy or a difficult simulated driving task. We predicted that speakers would introduce more redundancy in their descriptions in the difficult driving task, thereby accommodating the listener’s reduced cognitive capacity. The results showed that speakers did not adapt their descriptions to a change in the listener’s cognitive load. However, speakers who had experienced the driving task themselves before and who were presented with the difficult driving task first were more redundant than other speakers. These findings may suggest that speakers only consider the listener’s needs in the presence of strong enough cues, and do not update their beliefs about these needs during the task