Which of the following is a general sign that a person may have an intellectual developmental disorder (IDD)?

When considering the signs of an intellectual developmental disorder (IDD), erratic and unstable behavior can often indicate underlying cognitive or developmental challenges. Individuals with IDD may struggle with emotional regulation, social interactions, and adapting to new situations, which can manifest as inconsistencies in their behavior. This instability may stem from difficulties in understanding and managing their responses to various stimuli, signaling the need for support in developing adaptive skills.

The other options reflect abilities or traits typically associated with a level of cognitive functioning that is generally above what is seen in individuals with IDD. For instance, the ability to understand complex information and awareness of social norms suggest a higher level of cognitive processing and social comprehension than what would be expected. Similarly, excellent vocabulary skills imply a strong command of language that often correlates with higher intellectual functioning. Therefore, erratic and unstable behavior serves as a more relevant indicator of potential intellectual developmental disorder.