Final answer:
Behavior that contradicts verbal communication is a sign of ASD, highlighting the social communication difficulties the disorder presents.
Step-by-step explanation:
One behavior that demonstrates a potential sign of Autism Spectrum Disorder (ASD) is facial expressions, movements, and gestures that contradict the words said. This symptom is part of a broader set of social communication challenges in ASD, which includes difficulty in making and maintaining eye contact, reading social cues, and feeling empathy. The disorder is a spectrum, meaning symptoms can vary widely among individuals. Some may show repetitive motor behaviors like rocking, have a preoccupation with specific subjects, or show strict adherence to certain rituals. It's also notable that whilst some individuals with ASD may struggle with language, others may have good-to-excellent language skills and do not perceive their condition as a disorder, but rather a different way of processing information.