Symptoms of serotonin syndrome include all of the following EXCEPT:

In the context of serotonin syndrome, it is important to understand the typical symptoms associated with this condition. Serotonin syndrome is characterized by an excess of serotonin in the central nervous system and can present with a range of symptoms.

Muscle rigidity is a common symptom of serotonin syndrome, often associated with increased muscle tone and rigidity, particularly in severe cases. Dilated pupils may occur due to the autonomic dysregulation that can accompany heightened serotonin levels. Agitation is also a hallmark of this syndrome, as individuals may exhibit heightened arousal and restlessness.

In contrast, slowed reflexes do not align with the typical presentations of serotonin syndrome. In fact, the condition more often leads to enhanced reflex responses due to overstimulation of the nervous system, rather than a slowing down of them. Therefore, recognizing slowed reflexes as a symptom would not accurately reflect the clinical features of serotonin syndrome, making this the correct choice in the context of the question.