Who says religion and science can’t go together well? I just read an interesting paper by Kinzler et al.(1), published last year in the Proceedings of the National Academy of Sciences with apparent Biblical inspiration (OK, maybe not), as it begins with Judges 12:5-6 as an epigraph. In that passage, group membership is determined by having individuals pronounce a word, and if they can’t pronounce it properly, they’re killed. Kinzler et al. then provide a host of examples of what we might call linguistic discrimination in their opening paragraph:

The biblical story of Shibboleth speaks of the ancient massacre of those who could not correctly pronounce a phrase, thereby revealing their out-group status. Modern-day Shibboleth is ubiquitous: United States history alone abounds with examples of linguistic discrimination, from the severing of the tongues of slaves who spoke no English, to the forbidding of the public speaking of German during World War II and the execution of Russian speakers after the Alaskan purchase (1). Recent world history provides examples of linguicide paired with genocide of the Kurds in Turkey (2) and of imposed language policies initiating anti- Apartheid riots in South Africa (3). Favor for one’s native language group pervades contemporary politics in more subtle ways as well, for example, in recent debates concerning bilingual education, the politics of sign languages in deaf education, or proposals to make English the national language of the United States. (p. 12577)

The Biblical and historical examples lead them to hypothesize that linguistic differences may be at the root of in-group preferences and conflicts between social groups. And to provide evidence for this hypothesis, they conduct several studies with children under the age of five in which they pit native vs. non-native language speakers in social situations.

The first study, conducted with 5-6 month olds, involved showing the infants video of two adult English speakers, one of which was played forward (normal speech) and one of which was played backwards (reversed speech). After viewing the video, the infants were shown the two speakers next to each other, and their looking times were measured. This is a pretty common measure of infant preference: all things being equal, infants will look longer at the stuff they like the most, so you can measure relative preference by comparing how long an infant looks at two or more things. Kinzler et al.’s infants looked at the normal speech speaker 61% of the time, suggesting that, relative to the reversed speech speaker, they preferred the normal speaker. When the normal and reversed speech were paired with inanimate objects (in a separate experiment with different infants), the infants showed no preference for the object paired with normal speech. This suggests that the results of the first experiment did in fact have a social component: when people are involved, infants prefer people who speak a familiar language, or at least an actual language (reversed English only counts as a language on Black Sabbath albums). To make sure it was their native language, and not just actual language, that influenced infants’ preferences, Kinzler et al. conducted a third study pitting English against Spanish with infants from English-speaking homes (5-6 month olds don’t have a language, so calling it their native language is a bit misleading), and once again, they preferred their native language (61%).

Their fourth study placed infants in a more obviously social situation. In this case, ten-month olds from English-speaking or French-speaking homes watched videos of individuals speaking English or French. After the speaking videos, the infants saw a video of the two speakers handing them toys, after which the toys were placed on the table in front of the infants. Both the English-speaking and French-speaking infants picked the toy from the speaker who spoke their native language twice as often as they picked the toy from the other speaker.

Finally, Kinzler et al. showed five-year old native English or French-speaking children pairs of photos of other children. Each photo was first shown while a recording of either English or French was played. After they’d seen both photos paired with speech, the children were asked who they’d prefer to be friends with, and on average, both the English and French-speaking children chose the photos paired with their native language on seven out of eight trials.

This last study is unsurprising, of course. Children are unlikely to say they want to be friends with other children whose speech they can’t understand, but the infant studies seem to me to be pretty powerful demonstrations of the power of language in distinguishing between individuals, and perhaps social groups, for infants as young as 5 months old. What’s most striking about those results, perhaps, is that 5 month old infants don’t speak at all, but they’re still able to distinguish between “their” native language and other languages, and show a clear preference for people who speak it. Unlike in the case of the five year olds, then, this can’t be due to a desire to be around people whom they can understand.

How does this scale up to in-group prejudices and conflict? It’s hard to say, though it will be interesting to see further developmental research on the relationship between native language preferences and social preferences. For now, I suppose we’ll just have to take this as one more piece of evidence that we should all speak Esperanto.

¹Kinzler, K.D., Dupoux, E., & Spelke, E.S. (2007). The native language of social cognition. Proceedings of the National Academy of Sciences, 104(30), 12577-12580.