An observational study was carried out to investigate the behaviours displayed by Higher Functioning Autistic Spectrum Disorder children within a task environment. The computer based task, where the only factor being manipulated was degree of difficulty, tested executive functions of memory and planning. Behaviours were observed and analysed both within and between groups, the ASD participants being tested and compared with a typical developing age matched control group and, within the ASD group, participants with autism being compared with those participants diagnosed with Asperger’s Syndrome. Executive functioning and a possible relationship with adaptive behaviour was also investigated using standard scores obtained from the Vineland Adaptive Behaviour Scale in relation to final level achieved and also number of errors committed. The behaviours observed were classified at both general and more specific levels, facilitating analysis that captured the complexities of the behaviours displayed both at group and individual levels. Results showed some statistically significant results between the ASD group and control group, with the ASD group displaying more examples of negative behaviours than the control group, with more extreme behaviours (cross and tearful) being of importance. The within group analysis proved not significant with differences being attributed to individual rather than group effect. No relationship was found between executive functioning and adaptive behaviours. It was concluded that the behaviours of ASD participants were affected by task difficulty. Moreover, the findings reinforced the importance of acknowledging and recording the heterogeneity encompassed within the term ASD, and the importance of recognising and valuing the individual within the analytical framework.