Why does linguistic development differ from one child to another?

Children develop language skills at different rates. This is particularly evident during their first four years, but differences in linguistic ability remain up to school age, and also later in life. We do n0t know the reason for these differences, or their exact nature.

Do children differ only in their vocabulary and pronunciation, or also in their grammar and interaction with others? Is it conceivable that all children follow their own language curve, or are there a few potential pathways? And do they choose the route themselves or could it be due to the child’s interaction with their surroundings? These are some of the questions being addressed by the researchers in this project.

The reason for the project is that many studies of linguistic development in seemingly comparable groups of children arrive at differing findings. The children studied have been of the same ages, usually measured in months, and evaluations have been made using the same or similar language tests. The research team in the present project instead hopes to resolve the matter by studying the individual child’s development.

Over a seven-year period a longitudinal study of child language acquisition – the MINT project – followed 65 children and their parents starting when the children were three months old. Over the period (2013–2020), interactions between parents and children were filmed every three months, from when the children were three months old until they reached the age of four, as well as on three additional occasions up to the age of seven.

The children were filmed in a specially designed studio containing age-appropriate toys, cushions and soft toys. The children were also tested on their working memory, attentiveness, and ability to imitate and play symbolically. Their parents completed questionnaires about the family situation, income, education, siblings, number of languages spoken, etc. 

The researchers intend to reuse this extensive material to examine two h potheses about child language development. The first is that different children follow different curves for various language parameters: vocabulary, morphology, grammar, working memory, etc., but follow the same general development curve – their abilities develop in the same order but at different times. The second is that children’s language develops individually via different pathways without any shared trajectory. Factors other than age may then be a better basis for comparing children.