**3. Conclusion**

The greatest problem in autism research and indeed, psychiatry and clinical psychology generally is heterogeneity. It is impossible to get two samples of subjects completely identical and therefore, there are problems with generalisations to the general population. There was an attempt to establish, 'pure autism', with diagnostic instruments like ADI, but this was never possible to do and was never likely to be accomplished. The concept of, 'pure autism', does not exist. We have to develop more psychiatric and psychological models to deal with research in autism.

*Autism Spectrum Disorder - Profile, Heterogeneity, Neurobiology and Intervention*
