Personae under uncertainty: The case of topoi (2020)

Abstract: In this paper, we propose a probabilistic model of social signalling which adopts a persona-based account of social meaning. We use this model to develop a socio-semantic theory of conventionalised reasoning patterns, known as topoi. On this account the social meaning of a topos, as conveyed in a argument, is based on the set of idealogically-related topoi it indicates in context. We draw a connection between the role of personae in social meaning and the category adjustment effect, a well-known psychological phenomenon in which the representation of a stimulus is biased in the direction of the category in which it falls. Finally, we situate the interpretation of social signals as an update to the information state of an agent in a formal TTR model of dialogue.

## introduction consider the (somewhat dramatic) example 1, from @xcite , a corpus of dialogues where participants are instructed to resolve a moral dilemma. the subjects are asked to decide, based on limited information, who out of four passengers in a hot air balloon to sacrifice in order to save the other three. apart from communicating semantic content, arguments often implicitly evoke a topos, a pattern of reasoning the speaker draws on to warrant their argument. for example, the argument against sacrificing the pregnant woman (1-51) relies on a topos such as if you have to choose between killing n and m people and @xmath0. upon recognizing the evoked topos, an interlocutor may draw certain conclusions about the speaker, namely that they are the kind of person who reasons in this way. given example 1 39 c: well i'm not throwing a kid out [i just couldn't cope with it]. 42 a: and the other thing is i mean what what what she achieves er in her life if she becomes as famous as famous as mozart erm will go on er [forever]= 45 a: so i mean the person it seems like the person with least value is the . 48 b: [she's] pregnant. 51 b: [so you're] killing two people instead of one. ## personae, topoi, and social meaning in this section, we give background on the rhetorical and sociolinguistic phenomena we seek to model. ## two probabilistic models of social meaning in this section, we develop a simple probabilistic model that associates topoi with per-sonae. in particular, we model how the use of a topos by one agent results in an update to another agent's model of their persona. since we restrict our attention to a single utterance, we refer to the listener, whose internal state is updated, as self and the speaker, who evoked the topos, as other. we present two versions of the model. in the first-order model, self models other as a simple categorical probability distribution over personae. in the second-order model, self represents other as a dirichlet distribution over possible categorical distributions over personae. in both cases, the event being modelled is the same: other (o) invokes a topos (τ ) in a dialogue with self (s). then, self's updates their model of other as a result of that social signal. unlike the social signaling game from burnett (2017)'s, which is based on rational speech acts (frank and goodman, 2012), we do not assume any level of social recursion in the speaker; that is, the speaker does not consult a model of the listener's model of themself when producing an utterance. we assume that each agent has access to a set of personae, π = {π 1 , ..., π k }, and topoi, ψ = {τ 1 , ..., τ n }. a probability distribution ϕ π is assigned to each persona π such that: the probability given by ϕ π (τ ) is the likelihood that someone projecting π will evoke τ . this distribution models the idealogical association between topoi and personae-it is what gives the topoi their social meaning. for now, we assume that π, ψ and ϕ are shared community resources. we begin with the first-order model as a demonstration of the setting and, after discussing its weaknesses, move on to the second-order model. ## the category adjustment effect the category adjustment effect is a phenomenon in which the perception of a stimulus is biased in the direction of the centre of the category in which it falls. category effects are, for example, an explanation for why phonetic differences are easier to detect when they cross phoneme boundaries @xcite . the category adjustment model @xcite , describes the category adjustment effect in explicitly bayesian terms, with the category acting as a prior distribution over stimuli. @xcite , use this model to test a version of the sapir-whorf hypothesis. in a series of experiments they show that the semantics of colour terms have an effect on colour perception. for example, when asked to recall the colour of a displayed colour swatch, speakers were biased towards the mean of the colour category in which the swatch fell. @xcite defines the meaning of a linguistic variable, its indexical field, as the "con-stellation of ideologically related meanings" that arises in virtue of the variable's relationship with one or more personae. viewed through the lens of category adjustment, the social interpretation of a linguistic variable is mediated by the social categories (personae) associated with it. in our model, idealogical relatedness is represented by the conditional distribution of topoi given a persona (ϕ from §3). this distribution corresponds to the prior from the category adjustment model. this framework suggests two empirical questions for future work. the first question concerns the propagation of uncertainty about the projected persona. is it the case that, as in the original category adjustment model, the interpretation of a social signal is mediated by a single nearest category (the projected persona from §3.2), or does it take into account all of the personae that the speaker might be projecting (as in §3.1)? second, is there a category adjustment effect on the listener's judgment of which topos is being evoked? since we are focused on updates to the listener's model of the speaker's persona, we don't model uncertainty about the evoked topos, but a given argument may have multiple possible warrants. it seems reasonable to assume that the listener would take their persona model of the speaker and associations between personae and topoi into account when judging which topos was evoked. ## information state update in order to use the above technique to account for social meaning dynamics in interaction, we integrate our model with an information state update account of dialogue, an approach successfully used to model various dialogue phenomena @xcite . we see this as pointing to a general method for incorporating previous work on social meaning, for example, @xcite , into an account of incremental updates of social meaning in a idealogical context. this continues the work of @xcite . to represent the evolving information states of agents involved in interaction, we use dialogue gameboards @xcite @xcite . in order to account for coordination phenomena in dialogue, such as misunderstandings and clarifications, it is important that the information state of the participants are modelled as separate gameboards, representing each agent's view of the conversational game currently being played. the gameboards are split into two fields, one for information that the speaker takes to be private, one field for information that he or she takes to be shared in the dialogue. on our account dialogue participants are represented twice on the dgb. in figure 3 we see that the shared information about the participants is just referential. the information about perceived personae of the dialogue participants can be found in the private-field of the dgb, where the labels 'other' and 'self' are associated with the corresponding individuals in the shared field. the superscripted up arrow indicates that the path points to an object three levels up in the record type. as an interaction progresses the dgbs of the participants evolve in accordance with update rules. in figure 4 we represent the update rule 'f updatepersonae ' which is a function which takes an information state and an utterance event and returns a type for the updated information state. this function is used in the action rule 'updatepersonae' given in figure 5 . this action rule has three conditions. the first one requires that the agent's, s, current information state, s i,s , is judged by s to be of some type, t . the second condition requires that t is a subtype of the type required for r in 'f updatepersonae '. the third condition requires that the current utterance, u * , is of the type required for u in 'f updatepersonae '. if these conditions are fulfilled s is licensed or "afforded" (indicated by the wavy line) to make a judgement about s's updated information state, s i+1,s , namely that it of the type which s judged the current information state to be of asymmetrically merged, indicated by ∧ . with the result of applying the update function to the current information state and the current utterance. the operation of asymmetric merge on record types in ttr corresponds to priority unification in feature based systems. it will preserve all the information in both types except that if the two types have different information on a given path then the information from the second type will be in the result but not that from the first type. (see @xcite for more details.) these definitions rely on two types which depend on the set of topoi, ψ, which are currently under consideration. the first type is persona(ψ). a witness for this type is a distribution over ψ. (in a more complete treatment this would just be one of a number of components that make up a persona.) that is, f : persona(ψ) iff f is a function with domain ψ and range in [0, 1] such that @xmath1 the second type we use is persconcfunc(ψ), the type of persona concentration functions for ψ. this is defined as that is, persconcfunc(ψ) is the type of functions from distributions over ψ to positive real numbers greater than 0. ## conclusion in this paper we present a probabilistic model that accounts for the social meaning of topoi. we suggest that, as in the case of colour perception, the interpretation of social signals is subject to a category adjustment effect induced by social categories, or personae. finally, we incorporate this model into an integrated account of linguistic interaction. we do this by defining a ttr update rule which is referenced in an action rule showing how speakers change their model of their interlocutor based on social signalling. we see three major avenues for future work stemming from the basic model presented here. first, systems of social meaning are not monolithic or static-we should account for variation and change in the available personae, topoi, and the associations between the two. second, this model could be used in a game-theoretic analysis of argumentation. based on the persona that a speaker projects, which topoi should an interlocutor use to warrant their arguments? finally, as discussed in §4, how does the listener's model of the speaker persona affect which topos they interpret as warranting the speaker's argument?