You say tomato, I say the same: A large-scale study of linguistic accommodation in online communities (2023)

Abstract: An important assumption in sociolinguistics and cognitive psychology is that human beings adjust their language use to their interlocutors. Put simply, the more often people talk (or write) to each other, the more similar their speech becomes. Such accommodation has often been observed in small-scale observational studies and experiments, but large-scale longitudinal studies that systematically test whether the accommodation occurs are scarce. We use data from a very large Swedish online discussion forum to show that linguistic production of the users who write in the same subforum does usually become more similar over time. Moreover, the results suggest that this trend tends to be stronger for those pairs of users who actively interact than for those pairs who do not interact. Our data thus support the accommodation hypothesis.

## introduction language is a tool not only for conveying information, but also for expressing attitudes, constructing identities and building relationships @xcite . one manifestation of this fundamental property of language is that how we speak (or write) depends on whom we are speaking (or writing) to. how exactly the audience affects the linguistic production is a complex and multi-faceted process which can be approached from various perspectives. consider, for instance, the audience design theory @xcite , social identity theory @xcite and accommodation theory @xcite . in this paper, we perform a large-scale test of the hypothesis that people adjust their production style to their interlocutors. this phenomenon is known as accommodation (sometimes attunement or linguistic alignment) or convergence if the styles of the interlocutors are becoming more similar (divergence if they are becoming more different). while it has received considerable attention within sociolinguistics @xcite and cognitive psychology @xcite , large-scale longitudinal studies are wanting. an exception is a study by @xcite , who have observed a group of frenchspeaking children at a kindergarten for one year and shown that children who interacted more frequently adopted similar usages of a number of sociolinguistic variables (such as, for instance, the dropping of the consonant /r/ in post-consonantal word-final positions). internet and social media in particular provide us with a vast amount of data about how people communicate and how they use language for other purposes than information transmission @xcite . while in some respects these data are not as informative as those collected by direct observation or experimenting, in some other respects they may be equally or even more useful, providing very detailed information about who interacted when with whom and how. besides, it is often possible to collect large datasets that enable more systematic hypothesis testing. we use data from a very large swedish discussion forum (flashback) to test a widely held sociolinguistic assumption that "the more often people talk to each other, the more similar their speech will be" @xcite . in brief, we find pairs of flashback users which during some period of time have actively interacted (see section 2.2 for the definition of "active interaction"). we define a measure of linguistic distance between users and show that it is valid for our purposes (see section 2.3). for every pair of users, we then calculate the linguistic distance between the two users' production before they have started interacting (∆ bef ore ) and after it (∆ af ter ), and the difference between these distances (∆ @xmath0. if the convergence assumption is correct, we expect that the distance will tend to become smaller and the aver-age ∆ i will be positive. a positive ∆ i , however, can arise for different reasons, of which arguably the most prominent one is that distances between users become smaller not because users accommodate to specific interlocutors, but rather converge on a certain style adopted in the community @xcite . to test whether this is a better explanation, we perform a similar calculation for those pairs who have never had a single interaction, comparing texts written earlier (∆ early ) and later (∆ later ) during their activity on the forum (∆ @xmath1. if there is a convergence to norm, the average ∆ n should be positive. it is also possible that both pairwise accommodation and convergence to the community norm occur simultaneously. moreover, they might even be parts of the same process: if speakers do converge on a certain norm, this convergence can emerge (at least partly) due to pairwise interactions. it is, however, also possible that only one of these processes occurs. speakers can, for instance, converge on the community norm by adjusting to some perceived "average" style and not specific individual interlocutors. on the other hand, it can be imagined that speakers do adjust to the individual interlocutors, but that does not lead to the emergence of the community norm (for instance, because different interlocutors are "pulling" in different directions). the purpose of this study is to provide some insight into these not entirely understood processes. we envisage four likely outcomes of our experiments, summarized in ## results we perform the comparisons for all possible combinations of subforums (ten duplets in total). the results are summarized in remember that in the evaluation experiment (section 2.3) we roughly estimated the average distance between two different users to be around 0.13 for the chosen parameter values. while there clearly is large variation, and while the average distance can be larger for the main experiment (since the users' texts come from different subforums, not the same one), the estimate still provides us with a reference point and helps to put the observed distance changes in perspective. for home-sport-i, for instance, the average change is 0.033, which is approximately 25% of 0.13. this means that on average, actively interacting users in this duplet change their styles so much that they cover one quarter of an average distance the styles of two different persons. overall, the distance tends to become shorter both for interacting and non-interacting pairs. the we compare the observed results with the possible outcomes in out of nine duplets with sufficient sample size, seven demonstrate the effects which are compatible with either outcome 1 (overall convergence to a community norm and pairwise accommodation on top of that) or outcome 2 (just overall convergence) in ## discussion from section 3 it is clear that not all the results unambiguously point in the same direction. it is, however, obvious, that in most cases distance does become shorter, that is, users do converge. negative results (distance becomes longer) are not only less frequent, but also weaker than most of the positive ones. by comparing distance changes with the average distance between two different users we show that the effect sizes can be viewed as considerable. the shortening trend tends to be stronger and more robust for actively interacting pairs, but in some cases there is not enough evidence to prefer outcome 1 over outcome 2. more direct insight into the process of convergence would of course be desirable before it can be stated with certainty that it is caused by interactions. nonetheless, our results provide evidence that it actually can be so. in other words, we show that convergence can exist (a necessary condition is meant: distance changes are observed), but not that it definitely exists. note that while a reversed causal link can be suggested: users who have similar writing styles will interact more often, or "birds of a feather flock together" @xcite , it can hardly explain our results on its own: why would users who write on the same subforum and especially those who interact become linguistically closer over time? there are several reasons to why our results are not as clean as one might want them to be (apart from the obvious "random noise"). first, users in the pairs that we label as "non-interacting" can still interact in other flashback subforums. second, while we showed that cosine delta is a very good measure for linguistic distance, the definition of an interaction is more arbitrary. there is already a tradition of using the "post-nearby-in-the-samethread" measure @xcite , but it has not really been evaluated. overall, further exploration of the same (or similar) data is of course desirable. different experimental designs, different thresholds, different measures would show how robust the observed effects are. we find the following questions particularly appealing for future studies. ## conclusions we show that writing styles of users who participate in the same subforums do become more similar over time and that this increase in similarity tends to be stronger for pairs of users who actively interact (compared to those who do not interact), though this is not an exceptionless trend. these results support the accommodation hypothesis (let us repeat labov's wording: "the more often people talk to each other, the more similar their speech will be"). it is desirable to see if the observed effects can be replicated in similar studies with different experimental settings. all data and scripts necessary to reproduce the study are openly available. 4