Temple Grandin, an autistic woman involved in autism activism, described her inability to understand the social communication of neurotypicals, or people with typical neural development, as leaving her feeling "like an anthropologist on Mars". They may also not pick up on body language or social cues such as eye contact and facial expressions if they provide more information than the person can process at that time. They struggle with understanding the context and subtext of conversational or printed situations, and have trouble forming resulting conclusions about the content. This also results in a lack of social awareness and atypical language expression. How facial expressions differ between those on the autism spectrum and neurotypical individuals is not clear. Further, at least half of autistic children have unusual prosody.Autistic people may also experience difficulties with verbal communication. Differences in communication may be present from the first year of life, and may include delayed onset of babbling, unusual gestures, diminished responsiveness, and vocal patterns that are not synchronized with the caregiver. In the second and third years, autistic children have less frequent and less diverse babbling, consonants, words, and word combinations; their gestures are less often integrated with words. Autistic children are less likely to make requests or share experiences, and are more likely to simply repeat others words (echolalia). Joint attention seems to be necessary for functional speech, and deficits in joint attention seem to distinguish infants with ASD.
Some research has reported an overall brain enlargement in autism, while others suggest abnormalities in several areas of the brain, including the frontal lobe, the mirror neuron system, the limbic system, the temporal lobe, and the corpus callosum.In functional neuroimaging studies, when performing theory of mind and facial emotion response tasks, the median person on the autism spectrum exhibits less activation in the primary and secondary somatosensory cortices of the brain than the median member of a properly sampled control population. This finding coincides with reports demonstrating abnormal patterns of cortical thickness and grey matter volume in those regions of autistic peoples brains. Brain connectivity
Brains of autistic individuals have been observed to have abnormal connectivity and the degree of these abnormalities directly correlates with the severity of autism. Following are some observed abnormal connectivity patterns in autistic individuals:
Decreased connectivity between different specialized regions of the brain (e.g. lower neuron density in corpus callosum) and relative over-connectivity within specialized regions of the brain by adulthood. Connectivity between different regions of the brain (long-range connectivity) is important for integration and global processing of information and comparing incoming sensory information with the existing model of the world within the brain. Connections within each specialized regions (short-range connections) are important for processing individual details and modifying the existing model of the world within the brain to more closely reflect incoming sensory information.