Social Norms Guide Reference Resolution (2022)

Abstract: Humans use natural language, vision, and context to resolve referents in their environment. While some situated reference resolution is trivial, ambiguous cases arise when the language is underspecified or there are multiple candidate referents. This study investigates howpragmatic modulators external to the linguistic content are critical for the correct interpretation of referents in these scenarios. Inparticular, we demonstrate in a human subjects experiment how the social norms applicable in the given context influence theinterpretation of referring expressions. Additionally, we highlight how current coreference tools in natural language processing fail tohandle these ambiguous cases. We also briefly discuss the implications of this work for assistive robots which will routinely need to resolve referents in their environment.

## introduction humans interacting in natural language need to resolve referential expressions often referring to referents in their environment; utterances like pick up the green box or pick it up, for instance, highlight some referring expressions that point to a referent. these expressions appear in various forms, from clear and specific-the green box-to underspecified and ambiguous-it. but reference resolution, especially situated reference resolution, also requires vision and pragmatic context to disambiguate references. in the linguistically underspecifed example of pick it up, a listener may have to look for the candidate objects in the environment to figure out what it refers to. additionally, the social setting can modulate what referent is intended, given the same referring expression and objects in the environment; in a dining room, for instance, a spoon on the ground may be the more likely candidate than a pencil. in this paper we investigate the role of pragmatic modulators like this in reference resolution. the psycholinguistics literature has leveraged eye tracking to infer what referents humans resolve in various contexts @xcite . pragmatic modulators outside of the linguistic content can further constrain the referential domain and affect referent interpretation, such as task-relevant constraints @xcite . there is a gap, however, in understanding how other pragmatic modulators, such as social norms and conventions affect the interpretation of referents. for example, while there has been work on modeling what social norms are activated in various contexts and settings @xcite , it is unclear how norms guide humans to interpret referring expressions. similarly, conventions such as standing on the right side of an escalator while walking on the left, or sitting in the back of cab, can have modulatory influence on reference resolution and object selection. the aim of this paper is to demonstrate the role of pragmatic modulators, especially social norms, in guiding situated reference resolution. first we provide background on reference resolution and context, with a focus on situated reference resolution in particular. then, we show how referents are guided by social norms in certain contexts through a human-subjects experiment. we proceed to compare results from this experiment-the referents selected given the situational context and referring expressions-against several coreference tools that attempt to resolve these referents. lastly, with an eye towards assistive robots, we conclude by outlining an approach for teaching robots to leverage social norms and context for object selection. ## pragmatic constraints and social norms work on multi-modal reference resolution gets closer to modeling pragmatic constraints, mainly by moving beyond text and considering gesture and context to help disambiguate referring expres-sions @xcite @xcite . @xcite , in addition to speech and gesture, incorporates contextual knowledge to improve the accuracy of their model on a dataset where people refer to objects on a table. the model exploits information from the kitchen domain and uses recipes as a knowledge base to understand tools and ingredients that typically belong together. @xcite also uses domain knowledge in a graph-matching algorithm for multi-modal referring expressions with a map showing houses and prices. the guiding context, here, is conversational history and domain knowledge about house pricing. within the psycholinguistics literature, @xcite use eye-tracking in a cooking simulation to show that pragmatic constraints have modulatory influence on the interpretation of referring expressions. in this experiment, participants followed a confederate cook's instructions for a recipe, where the cook used the the definite noun phrase the cake mix to signal potential referents in the cooking space. the addressee's domain of interpretation changed with the task-based constraints-cued perceptually with the cook's hands being empty or full. as the addressees monitor the speaker, they tend to interpret the referent in the cook's area when the cook's hands were full and the referent in their own area when the cook's hands were empty. the results support constraint-based models, where speaker constraints are taken into account for interpretation alongside linguistic ones; indeed, this study highlights how a definite referring expression can point to a few possible candidate objects in a restricted domain, just based on its linguistic form, yet people can disambiguate which referent is being referred to from the pragmatic context. while this study focuses on speaker-based constraints, there is still a lack of knowledge about the modualtory influence of social norms and conventions in interpreting referring expressions. a promising step in this direction are attempts to computationally model social norms with the ultimate aim of creating norm competent artificial agents @xcite . malle et al. (2020) experimentally collected responses from humans to generate social norms for eight contexts, including a library, boardroom, bathroom, and restaurant, among others. while social norms can be elusive and challenging to define, since they vary by cul-ture and appear on various levels of demand, malle et al. (2020) follows janoff-bulman et al. (2009) in viewing social norms as prescriptions and prohibitions and giving attention the gradability of these norms by mapping the deontic force-how strong or weak these norms are to be followed-to the collected prescriptions and prohibitions. malle et al. (2020) define norms more formally as such: a norm is an instruction, in a given community, to (not) perform an action in a given context, provided that a sufficient number of individuals in the community (i) demand, to a certain degree, of each other to follow the instruction and (ii) do in fact follow it. we will adopt this definition for social norms in this study, which formalizes the idea of prescriptions and prohibitions being followed by many people. we also broaden the definition of social norms to include descriptive norms and conventions, although @xcite makes a more fine-grained distinction between social norms, conventions, and descriptive norms. we do not consider moral norms or legal obligations in the present paper. equally important, this study offers an approach for teaching norms to robots for guiding actions and balancing norms with goals. they outline an enriched markvov decision process (mdp) approach that uses a starting norm base, which are predefined norms collected in the experiment, and refines it through human interaction and feedback. we look at this proposal optimistically for, in a similar vein, teaching embodied agents the specific behavior of performing situated reference resolution. a referring expression can appear in a variety of linguistic forms, but pragmatics, regardless of the linguistic form, has the potential to modulate the meaning of the sentence and referent entirely. this will be true for humans that use natural language with robots as well. imagine a situation where someone commands an assistive robot in a home: take it away. the robot can use the natural language and vision input to scan the area for potential referents of it. if a shoe and a spoon are salient objects on a dining room table, the convention of a shoe not belonging on a table would make the shoe the more likely candidate. alternatively if a shoe and a spoon are salient objects on the floor of a bedroom, the spoon would likely be the referent. marrying the work on pragmatic constraints on reference resolution and social norms, we conduct an experiment where humans are tasked with identifying the referent of an ambiguous referring expression across various contexts and, thus, various social norms and conventions. this experiment relates to previous work that leverages crowd sourcing for collecting anaphora annotations and judgments @xcite @xcite . although this body of work focuses on a game-with-a-purpose (gwap) approach to crowd sourcing @xcite , our study does not gamify our annotation task but it does avoid using linguistic and annotation terminology for participants. @xcite , specifically, collects several judgements and disagreements over ambiguous cases of anaphora. similarly, our study captures the reasons and explanations people make when resolving a referent, although there is no adjudication process. through overall decisions and explanations, we are then able to study the agreement and interpretations over our ambiguous scenarios. ## experiment and results here, we report the details of an online vignettebased human-subjects experiment designed to explicate the potential role of social norms in resolving references in context. we recruited 50 participants on prolific (see https://prolific. co ), an online participant recruitment site which is known to provide better results on tasks like ours. participants were free to leave the study at any point, their data was anonymized, and they received adequate payment for the study. a consent form was presented at the beginning of each study with information on how their data would be used. we restricted our recruitment to people living in the united states and at the time of the study and native speakers of english. each participant was presented with eight text vignettes where each vignette described a scene within a daily-life context. each scene contains four pieces of information: an explicit mention of the setting (the scene takes place in a library), a description of the background-that is, the objects and people in the scene-an underspecified referring expression (e.g., remove it), and an actor in the scene acting on an object. there are always two salient referents that are potential candidates for the referring expression. participants must determine whether the referent chosen by the actor in the scene was the correct one. with the information still in view, participants are asked to select the best explanation for their answer and are provided a multiple choice listing of five potential explanations and one open text response option labeled other. these reasons include: typical for the setting, object is mentioned first, object is mentioned more recently, time sensitive option, more convenient option, and other. we included reasons that could explain that the correct referent was the one that was intended, rather than subjective options that potentially frame the question as a personal preference. we also offered a text response if none of the options fit. 1 we summarize the contexts, candidate objects, and a hypothesized norm associated with each context in each context, some of which are inspired by @xcite , are assumed to activate their own inventory of norms to help disambiguate the referring expression. our hypothesized norms are partly based on intuition but also inspired by previous work on norms and behavior. @xcite , for instance, conducted a survey with undergraduates to confirm the normative behavior of acting silently in a library setting. this norm is applied to our study in a library scene: there is an open seat at a table right next to someone and a seat further away from someone. although there is no mention to noise, seating right next to someone else-a stranger-is potentially noisy and interruptive. additionally, similar to the norm of not littering @xcite , we focused on 1 the experimental design of a posthoc explanation of whether the referent was "correct" was chosen after initial pilot experiments showed that asking subjects for the correct referent rather than providing them with the choice of the actor in the scene led to a confound: subjects often choose the referent they would have chosen instead of hypothesizing the referent the actor in the given context would have selected. similar to winograd schema datasets, each referring expression is stripped of linguistic surface cues such as gender, number, and person that would give away the referent. instead, these scenes are set up so that subjects in the experiment have to rely on information outside of the text to help them make a decision. the only linguistic cue we maintain in the study, however, is recency, where we change the ordering of the referents. these scenes include: library, boardroom, taxicab, friend's car, dining room, leather shop, bookstore, home bathroom. each scene has a complementary scene that shares the same referents; the library and boardroom share two seats, the taxicab and friend's car share two seats, the dining room and leather shop share a shoe and a spoon, and the bookstore and home bathroom share a toothbrush and a magazine. the purpose of creating complementary scenes with the same referent was to demonstrate how, when the referring expression is constant, the context, and thus the social norms and conventions associated with it, modulate the interpretation of the referent. we posit, for instance, that people will select the seat in the back of the cab as opposed to the front of the cab. this would be guided by the norm of sitting in the back of a cab. alternatively, people would most likely choose to sit in the front seat in a friend's car and not the back seat, also for conventional reasons. the following excerpts show examples of the scenes participants read during the experiment. the one below is for the dining room context: the scene takes place in a dining room. there is a shoe and a spoon sitting on a dining room table. dinner is about to be served. someone says, "remove it." someone else removes the shoe from the table. this next example, describing a leather shop, shows a complementary scene using the same candidate objects of the shoe and spoon and the same definite referring expression, remove it. the scene takes place in a leather shop. there is a spoon and a shoe sitting on a worktable. nothing else is on the table. a customer is coming into the store. pointing to the worktable, someone in the room says, "remove it." the employee removes the spoon. while each participant sees all eight scenes, there are two conditions where the ordering of the referents mentioned in the text are flipped. condition a lists the intended (correct) referent last and condition b lists the intended referent first. in the dining room scene, for instance, condition a lists the spoon first and then the shoe and condition b lists the shoe first and then the spoon. we create these conditions to test whether people are biased by the recency of referents and to also evaluate these texts on coreference tools which may be biased by recency in performing reference resolution. the results in then there are the bookstore and home bathroom scene that have a lower consensus and, thus, a higher count of alternative explanations. interestingly, when people disagree that the selected object was correct, their explanations suggest a normative reason is stronger in the other direction. for example, if a magazine is more conventional in a bookstore (prescription) a toothbrush is unconventional and suggests a prohibition norm. we present a sample of explanations for these scenes: bookstore: toothbrush doesn't belong... the toothbrush is the more out-of-place object, and therefore, it is implied to have that removed rather than the magazine the toothbrush does not match the setting/misplaced home bathroom: object is irrelevant to the setting and should be removed we also note that for these scenes and others in the study, some of the explanations people articulate can be classified as norms even though they did not select the normative option in the multiple choice: home bathroom: the toothbrush should not be on the floor toothbrush does not belong on the floor ## discussion & future implementations the coreference task performed by humans and the nlp tools show a striking difference in outcomes. given the same context and text, people tended to agree on the correct referent. since the examples were stripped of linguistic cues that would give away the referent, people relied on context and social norms based on the reasons they selected and the written explanations they provided. notably, however, the inconsistent agreement across all scenes can be reconciled with the fact that social norms and conventions are not equally shared across all people. this is supported, in part, by the written responses too. additionally, these results also suggest that not every norm is weighed the same; the deontic force-how strongly the norm is to be followed-potentially influences how the norm guides a behavior or interpretation and competes with other norms. admittedly, a limitation of our study is that we do not explicitly categorize our hypothesized social norms and conventions in a gradable fashion, but future work will consider deontic force for a more fine-grain understanding of social norms. nlp tools, on the other end, tell a different story. many of the tools specifically designed for coreference resolution failed to consistently select the correct referent. the more powerful nlp engines, such as gpt-3 model, also performed poorly. this shows that relying on such a system to resolve references in these contexts would be problematic. the davinci model when prompted by the question which one? justifies its response with an explanation of grammatical appropriateness: if we use the noun that appears in the context, it is clear that the speaker is referring to the toothbrush. there is no other "it" in the sentence... we would never say, "pick up the magazine." this is why it's important to know whether the noun is the subject or object of a sentence. this explanation echoes something meaningful about grammar, yet is faulty and unclear. rather, this argument is produced from statistical correlations the system extracted from large corpora. furthermore, the system has no understanding of norms or how to apply them. the potential danger, here, is that simply employing deep learning systems without giving them a sense of norms will lead such systems to also violate norms. while the consequences of breaking norms can range in severity, at the most extreme end, they can include harm to other people. a norm aware reference resolution system, therefore, will not only help to disambiguate referents but help a system know what not to do. this is especially important with embodied agents whose actions in the real world will be influenced by its reference resolution capabilities and natural language understanding. ## conclusions we conducted a human subjects study to demonstrate how social norms can guide reference resolution. given a text vignette and a referring expression stripped of linguistic cues, the majority of subjects confirmed the intended referent in each context and relied on knowledge of conventions to make their decision. in contrast, several nlp tools evaluated on the same examples consistently failed to select the correct referent. we argue that these nlp tools critically lack an understanding of conventions and social norms and should not be completely relied on for reference resolution as they can also violate norms. finally, we integrate our findings into designing a methodology for teaching robots to use social norms and conventions to perform situated reference resolution. in future work, we experiment with using visual scenes for activating norms and evaluate larger nlp models with fine-tuning to our task. lastly, we will implement our methodology into a cognitive architecture and look more closely at how the gradability of social norms influences reference resolution.