Which of the following symptoms is indicative of a cluster A personality disorder?

Flat affect is a symptom often associated with cluster A personality disorders, particularly Schizoid Personality Disorder, which feature presentations of social withdrawal and emotional detachment. Individuals with cluster A disorders tend to display odd or eccentric behaviors, and a flat affect indicates a lack of emotional expression, which aligns with this characteristic. Those with such personality disorders may struggle to express emotions or connect with others, leading to an appearance of indifference or emotional blunting.

In contrast, the other options highlight traits that are not typically associated with cluster A disorders. Excessive sociability, for instance, suggests an outgoing personality, which does not fit the withdrawal and isolation characterizing this group. Similarly, a charming personality implies a level of social engagement and warmth that is at odds with the emotional distance seen in cluster A. Impulse control relates more to cluster B personality disorders, where emotional dysregulation and impulsivity are more prominent. Thus, identifying flat affect as indicative of a cluster A personality disorder is accurate given its affiliation with emotional detachment and social withdrawal inherent to that classification.