Studying compositionality in infants

The concept of compositionality is the ability to combine known ideas together to create novel concepts. For example, the term 'different' ' is formed by combining 'same' and 'not'. An EU-funded study, 'Compositionality in infants' (COIN), examined whether infants have discrete mental symbols that represent 'same' and 'different' and whether they represent 'different' as 'not same'.

Previous research suggested that infants can learn how certain elements can predict an event. For example, they were able to learn that certain vowels predict a puppet appearing on a specific location on a screen, but they could not simultaneously learn that the type of vowel also predicts the type of puppet. This may mean that infants cannot learn two concepts in parallel.

To answer this question, researchers tested whether 14-, 18- and 24-month–old babies could learn that a dog picture means an object appears on the right and a car object means an object appears on the left. Researchers found that babies only learned the dog picture relationship, confirming the hypothesis that babies cannot learn two concepts in parallel.

Researchers then developed a novel experiment to test whether babies interpreted 'different' as a discrete concept or as 'not same'. They adapted the Match-to-Sample (MTS) and Mismatch-to-Sample (mMTS) paradigms typically used in animal experiments.

Using both paradigms, researchers gave participants a sample with A and either A or B. They tested infant eye tracking to determine if and how babies learned each paradigm. Results showed that 14-month–old babies can learn both paradigms, but there is evidence suggesting that they understand the 'different' paradigm as 'not same'. Other studies suggest that children can understand the words 'same' and 'different' at around age 3 or 4, but do not separate the concepts until around age 5.

Results of this study shed light on how babies learn compositionality, an ability at the core of productivity. Although researchers found no evidence for compositionality before appropriate language emerged, they are continuing their work to better understand this key relationship.