Non-verbal Behavior at Age 2 is significantly related to Language, Communication, and Social Outcome at Age 7
Charman et al. (2005) found that non-verbal behaviour was relatively robust and reliable on the different measurements over time, whereas the other indicators where not so reliable. In that light non-verbal behaviour might be a good indicator for the development of language and communication skills specifically and quality and frequency of social interactions in general (in the long run [heterotypical development]). Non-verbal behaviour might also be an indicator of the intrinsic motivation to learn socially. That motivation might explain why non-verbal behaviour at age 2 predicted later language, communication and social skills. This is also a good example how developmental psychopathology can increase the knowledge about the processes involved in the development of a disease.