Behavioural toxicity is a very applicable area in the vast field of ecotoxicology where,assessment of the alteration of behaviour is an effective tool to evaluate neural activity in an organism. In our present study, we have shown that arsenic trioxide exposure can stimulate repetitive grooming activity in a freshwater prawn, Macrobrachium lamarrei; however, over time the organism can modulate the grooming performances to less. We predict that repetition in the grooming behaviour is a case of neurotoxicity by arsenic and induction of Autism Spectrum Disorder (ASD) within a short period of exposure time.