By Matthew Warren

The idea that more talkative parents have children with superior language or cognitive skills has a long – and sometimes controversial – history. An influential study from the early 1990s claimed that American children from lower socioeconomic backgrounds have poorer language development because they hear fewer words from their parents. But scientists have pointed out several issues with this early research – including that it involved researchers going into people’s homes to record them, potentially affecting the language they used.

Since then, other researchers in the United States have researched families’ use of language in a less intrusive way – and found that any effects may be more subtle than originally claimed. Now, in what they say is the “largest naturalistic observation study of early life home environments to date”, scientists have brought these methods across the pond. A study of more than 100 London families, published recently in Developmental Psychology, has found that the quantity of language used by parents is related to children’s cognitive skills – but exactly why remains unclear.

Katrina d’Apice from the University of York and her colleagues equipped 107 children aged between two and four with wearable devices that recorded all language spoken by them or their family for three days. Software then automatically processed the recordings, which averaged 15 hours per day, to calculate how many words were spoken by the adults in the family. The children also completed a series of cognitive tests, which involved tasks like copying and drawing.

The researchers found that adults spoke an average of 17,800 words per day – but this varied considerably. Even within families, the number of words spoken by adults across different days was only moderately correlated. “Our findings emphasize that early life experiences, especially with regard to language, are dynamic processes that change and evolve over time, rather than static environmental determinants,” the researchers said.

Nevertheless, the team found that, overall, adult word counts were related to children’s cognitive skills: children whose parents used more words tended to do better in the cognitive tests.

The team also looked at the richness of parents’ and children’s vocabulary, finding that children had a greater lexical diversity when adults’ vocabulary was also more diverse.

The correlational design of the study means it’s impossible to tease apart cause and effect, so there are a number of possible explanations for the findings. It could be that more exposure to language fosters children’s intelligence, for example. Or parents could simply be stimulated to talk more when their children are smarter. There could also be shared genetic effects influencing both the parents’ language and children’s cognitive abilities.

Whether these results generalise to other groups remains to be seen – more than 80 per cent of parents in this study held a university degree; almost all of them were married; and they were mostly high socio-economic status. Nevertheless, the use of discreet recording devices and automatic language processing software would seem to open up the field to many more naturalistic studies like this in the future.

— A naturalistic home observational approach to children’s language, cognition, and behavior

Matthew Warren (@MattbWarren) is Staff Writer at BPS Research Digest