The triad of impairments has been used for 30 years and has been the main principle that has been used to understand autism. Recently, the triad model has been reduced to only two areas of impairment and is know known as the the dyad. The dyad's features only two areas which are social communication and social interaction and restricted, repetitive patterns of behaviour, interest or activities - including sensory activities. Despite the new model being used there are still many researchers that prefer the triad and see the positives of using this original model. These positive points include the fact that the triad identifies more underlying impairments and this allows the diagnosis to be made with the most accuracy, furthermore, the model
