What are beta waves, and when are they typically observed?

Beta waves are brain wave patterns characterized by their fast frequency, typically ranging from 12 to 30 Hz. They are most commonly associated with active, alert, and engaged mental states where cognitive processes such as problem-solving, decision-making, and focused attention occur. These waves are prevalent when an individual is awake and actively thinking or concentrating, indicating a state of heightened alertness.

In contrast to slow waves observed during deep sleep, beta waves represent a completely different state of brain activity related to cognition and awareness. Irregular waves can indicate various levels of brain function or distress but are not specifically linked to beta waves. Medium waves, while they might suggest relaxation, would generally correlate more with alpha waves, not beta waves. Thus, the association of beta waves with active and alert thinking makes this answer the most accurate choice.