The lack of demonstrated empathy is possibly the most dysfunctional aspect. Individuals experience difficulties in basic elements of social interaction, which may include a failure to develop friendships or to seek shared enjoyments or achievements with others, a lack of social or emotional reciprocity, and impaired nonverbal behaviors in areas such as eye contact, facial expression, posture, and gesture.

Patients are not usually withdrawn around others; they approach others, even if awkwardly. For example, they may engage in a one-sided, long-winded speech about a favorite topic, while misunderstanding or not recognizing the listener's feelings or reactions, such as a need for privacy or haste to leave. This social awkwardness has been called "active but odd". This failure to react appropriately to social interaction may appear as disregard for other people's feelings, and may come across as insensitive. However, not all individuals will approach others. Some of them may even display selective mutism, speaking not at all to most people and excessively to specific people. Some may choose to talk only to people they like.

The cognitive ability of Patients often allows them to articulate social norms in a laboratory context, where they may be able to show a theoretical understanding of other people's emotions; however, they typically have difficulty acting on this knowledge in fluid, real-life situations. Patients may analyze and distill their observation of social interaction into rigid behavioral guidelines, and apply these rules in awkward ways, such as forced eye contact, resulting in a demeanor that appears rigid or socially naive. Childhood desire for companionship can become numbed through a history of failed social encounters.

Patients often display behavior, interests, and activities that are restricted and repetitive and are sometimes abnormally intense or focused. They may stick to inflexible routines, move in stereotyped and repetitive ways, or preoccupy themselves with parts of objects.

Pursuit of specific and narrow areas of interest is one of the most striking features. Patients may collect volumes of detailed information on a relatively narrow topic such as weather data or star names, without necessarily having genuine understanding of the broader topic. For example, a child might memorize camera model numbers while caring little about photography. Although these special interests may change from time to time, they typically become more unusual and narrowly focused, and often dominate social interaction so much that the entire family may become immersed. Because narrow topics often capture the interest of children, this symptom may go unrecognized.