Witzelsucht (from the German "witzeln", meaning to joke or wisecrack, and "sucht", meaning addiction or yearning) is a set of rare neurological symptoms characterized by a tendency to make puns, or tell inappropriate jokes or pointless stories in socially inappropriate situations. A less common symptom is hypersexuality, the tendency to make sexual comments at inappropriate times or situations. Patients do not understand that their behavior is abnormal, therefore are nonresponsive to others' reactions. This disorder is most commonly seen in patients with frontal lobe damage, particularly right frontal lobe tumors or trauma. The disorder remains named in accordance with its reviewed definition by German neurologist Hermann Oppenheim; its first description as the less focused "Moria" ("stupidity"), by German neurologist Moritz Jastrowitz, was in 1888.

Due to similarity of symptoms of the disorder to the mannerisms of Batman's arch-rival Joker, it is sometimes known as 'The Joker Syndrome'

In both case studies, patients showed an altered sense of humor, mostly in regard to producing and appreciating humor. The right hemisphere is involved with processing speed and problem solving, which plays a role in humor processing. These patients have difficulty fully interpreting a joke's content, but can recognize the importance of the form of a joke. Patients with witzelsucht often find non sequiturs, slapstick humor, and puns funniest since these forms of humor do not require integration of content across sentences. In other words, the end of the joke is not dependent on the first part; one does not need to make a logical connection to understand humor. Patients show no change in understanding simple logic, and understand the importance of surprise in humor (hence why they choose slapstick humor instead of the “correct” punch line); however, once they have registered this surprise, they cannot connect the punch line to the body of the joke to fully appreciate the true humor behind the joke. Successful jokes require a juxtaposition of the sound and the meaning of words used to understand the punch line. However, patients with witzelsucht have difficulty connecting the two, resulting in an inability to appreciate humor.

Additionally, patients show no emotional reaction to humor, whether produced by themselves or others. This lack of responsiveness is due to dissociation between their cognitive and affective responses to humorous stimuli. That is, even when a patient understands that a joke is funny (based on quantitative brain activity), they do not respond with laughter, or even a smile. While they have grasped the cognitive basis of humor, they do not affectively respond. This also considered a cognitive component of empathy, affecting ability to take the perspective of others; hence why patients often do not respond to humor produced by other people.