Final answer:
Ritalin's efficacy in treating ADHD suggests that the condition involves understimulation of dopamine transmission, since the drug increases dopamine activity in the brain regions critical for impulse control.
Step-by-step explanation:
The observation that Ritalin is an effective treatment for attention-deficit/hyperactivity disorder (ADHD) suggests that ADHD results from understimulation of dopamine transmission. Ritalin, or methylphenidate, is a medication that works by blocking the reuptake of dopamine, which increases neurotransmitter activity in areas of the brain associated with impulse control, like the prefrontal cortex and basal ganglia. The increase in dopamine activity helps to manage the symptoms of ADHD, including improving impulse control and reducing hyperactivity and inattention.