AP Psychology Practice Test 2025 - Free AP Psychology Practice Questions and Study Guide

Stimulants are substances that increase neural activity and elevate various body functions. They are known for their ability to enhance alertness, attention, and energy levels by stimulating the central nervous system.

The correct choice identifies "reducing neural activity" as the option that is not an effect of stimulants, as this is contrary to their primary function. Instead of lowering neural activity, stimulants like caffeine, nicotine, and amphetamines work to increase it, leading to a heightened state of arousal and vigilance.

The other options accurately describe effects associated with stimulants. For instance, stimulating substances excite neural activity and speed up body functions, resulting in increased heart rate, heightened alertness, and a surge in energy levels. Additionally, these substances often lead to noticeable changes in mood, ranging from increased euphoria to elevated energy levels, due to their effect on neurotransmitter systems.