Can the age at which an individual speaks his / her first words be used to predict the individual's mental ability?

Answer: Yes. True, it can be used to predict an individual mental ability

Explanation: Research conducted on social interaction, social communication, interests, behaviour etc on individuals has been proven to conclude that the mental ability of an individual can be predicted by when an individual first speak their first word.

One of the features of ASD (Autism Spectrum Disorders) is deficiency in language and communication and ASD is characterized by abnormal social interaction and communication, restricted interests, highly repetitive behaviour, and eccentricity. In which, all these are factors that can be used to determine one's mental ability.