**Abstract**

Synaesthesia is a nonpathological sensory perception that happens when a particular sensory stimulus elicits a sensory response in another modality. For example, hearing a word results in the perception of colors. Autism, a neurodevelopmental disorder, is characterized by differences in sensory perception (hyper/hypo). Some research has been done to understand the co-existence of synaesthesia in autism. Although autism and synaesthesia seem to be unrelated, the prevalence of synaesthesia in autism is three times higher than in the general population. This could be attributed to the excessive neuronal connections and activities in both conditions. Based on clinical observations and case studies, this chapter talks about how some of the problems that children with autism spectrum disorder (ASD) have with processing their senses contributes to synaesthetic ability. It also talks about how understanding and using these similarities helped the children develop their language skills.

**Keywords:** synaesthesia, ideasthesia, sensory processing disorder, savant syndrome, Asperger's syndrome
