Societies of strangers do not speak less complex languages

Many recent proposals claim that languages adapt to their environments. The linguistic niche hypothesis claims that languages with numerous native speakers and substantial proportions of nonnative speakers (societies of strangers) tend to lose grammatical distinctions. In contrast, languages in small, isolated communities should maintain or expand their grammatical markers. Here, we test these claims using a global dataset of grammatical structures, Grambank. We model the impact of the number of native speakers, the proportion of nonnative speakers, the number of linguistic neighbors, and the status of a language on grammatical complexity while controlling for spatial and phylogenetic autocorrelation. We deconstruct “grammatical complexity” into two separate dimensions: how much morphology a language has (“fusion”) and the amount of information obligatorily encoded in the grammar (“informativity”). We find several instances of weak or moderate positive associations but no inverse correlations between grammatical complexity and sociodemographic factors. Our findings cast doubt on the widespread claim that grammatical complexity is shaped by the sociolinguistic environment.

Table S1.The overview of Grambank features in metrics of fusion and informativity.The score of "1" is assigned to the fusion features if they are present in respective languages.Features that receive "0" are not involved in the fusion metric.Informativity metric assigns the score of "1" for the presence of at least one feature within the labelled group of features.The features that do not contribute to the informativity metric are indicated as "0".

GB074
Are there prepositions?0 0 GB075 Are there postpositions?0 0 GB303 Is there a phonologically free antipassive marker ("particle" or "auxiliary")?0 antipassive GB520 Can aspect be marked by a non-inflecting word ("auxiliary particle")?0 aspect GB519 Can mood be marked by a non-inflecting word ("auxiliary particle")?0 mood GB299 Can standard negation be marked by a noninflecting word ("auxiliary particle")?0 0 GB317 Is dual number regularly marked in the noun phrase by a phonologically free element?0 dual GB320 Is paucal number regularly marked in the noun phrase by a phonologically free element?0 paucal GB318 Is plural number regularly marked in the noun phrase by a phonologically free element?0 plural GB316 Is singular number regularly marked in the noun phrase by a phonologically free element?0 singular GB319 Is trial number regularly marked in the noun phrase by a phonologically free element?0 trial

GB262
Is there a clause-initial polar interrogative particle?0

GB263
Is there a clause-final polar interrogative particle?0

GB264
Is there a polar interrogative particle that most commonly occurs neither clauseinitially nor clause-finally?0

GB521
Can tense be marked by a non-inflecting word ("auxiliary particle")?tense

GB071
Are there morphological cases for independent personal pronominal core arguments (i.e.S/A/P)?0

GB146
Is there a morpho-syntactic distinction between predicates expressing controlled versus uncontrolled events or states?control

GB047
Is there a productive morphological pattern for deriving an action/state noun from a verb?0

GB048
Is there a productive morphological pattern for deriving an agent noun from a verb?0

GB049
Is there a productive morphological pattern for deriving an object noun from a verb?0

GB073
Are there morphological cases for independent oblique personal pronominal arguments (i.e.not S/A/P)?0

GB148
Is there a morphological antipassive marked on the lexical verb?antipassive

GB091
Can the A argument be indexed by a suffix/enclitic on the verb in the simple independent clause? 1 0

GB092
Can the A argument be indexed by a prefix/proclitic on the verb in the simple independent clause? 1 0

GB093
Can the P argument be indexed by a suffix/enclitic on the verb in the simple independent clause? 1 0

GB094
Can the P argument be indexed by a prefix/proclitic on the verb in the simple independent clause? 1 0

GB086
Is a morphological distinction between perfective and imperfective aspect available on verbs?

GB188
Is there any productive augmentative marking on the noun (exclude marking by system of nominal classification only)?

GB275
Is there a bound comparative degree marker on the property word in a comparative construction?

GB187
Is there any productive diminutive marking on the noun (exclude marking by system of nominal classification only)?
1 diminutive GB170 Can an adnominal property word agree with the noun in gender/noun class? 1 0

GB172
Can an article agree with the noun in gender/noun class?0

GB198
Can an adnominal numeral agree with the noun in gender/noun class?0

GB119
Can mood be marked by an inflecting word ("auxiliary verb")?mood

GB312
Is there overt morphological marking on the verb dedicated to mood? mood

GB107
Can standard negation be marked by an affix, clitic or modification of the verb?0

GB171
Can an adnominal demonstrative agree with the noun in gender/noun class?0

GB184
Can an adnominal property word agree with the noun in number?0

GB185
Can an adnominal demonstrative agree with the noun in number?0

GB186
Can an article agree with the noun in number?0

GB043
Is there productive morphological dual marking on nouns?dual

GB166
Is there productive morphological paucal marking on nouns?paucal

GB044
Is there productive morphological plural marking on nouns?plural

GB042
Is there productive overt morphological singular marking on nouns?singular  Table S4.The quantiles (0.025, 0.5, and 0.975) of estimates of the fixed effect of the number of L1 speakers (log-transformed to the base of 10 and standardized to have a mean of 0 and variance of 1) in three models predicting morphological complexity scores (used in Lupyan & Dale (6)) without and with random effects.The differences in sample size depend on 1) whether the WALS languages with calculated morphological complexity scores are also available on the global tree and in Glottolog with specified location data (the prerequisites for including spatiophylogenetic effects in the model) and 2) whether the model was fit for all available languages or only those for which at least 35% of the relevant features are available in WALS.

Table S5 . WAIC values of spatiophylogenetic models of fusion and informativity with fixed and random effects using different priors
The default feature coverage threshold refers to the cut-off used in the Lupyan & Dale (6) study: at least 3 available features out of 28 (~10%) WALS features included in the morphological complexity metric.