Stereotypies are repetitive, invariant behaviors with no obvious goal or function, often observed in captive animals, mentally ill or handicapped humans, and subjects given stimulant drugs. They are considered abnormal but may result from normal behavioral processes. Stereotypies are often linked to sub-optimal environments and are used as welfare indicators. While some hypothesize they have beneficial consequences that reinforce their performance, other factors like positive feedback may explain their persistence. Empirical evidence suggests they may lower awareness of external events and reduce arousal and distress, though the causal relationship remains uncertain. Stereotypies vary in origin, causation, and characteristics, and can change over time. Stereotypies resemble normal behaviors in being invariant and resistant to change, and can become independent of their original stimuli. They may develop in animals facing insoluble problems or due to brain damage, psychiatric conditions, or drugs like amphetamine. Stereotypies are diverse, varying by species, eliciting situations, and individual differences. Examples include rocking movements in humans, bar-chewing in sows, head-swinging in bears, and pacing in foxes. Stereotypies are often seen in environments that seem sub-optimal, associated with lack of stimulation, stress, or frustration. They may result from past challenges or environmental factors, and some may involve self-damage. Stereotypies can be reinforced by providing alternative behaviors or reducing arousal, but their persistence may also be due to other factors like sensory input or endogenous opioids. While some evidence suggests stereotypies may have a coping function, others indicate they may not always be beneficial. The data is often correlational, making it difficult to determine causation. Stereotypies may be symptoms rather than causes, and their effectiveness as a coping response depends on the individual and context. Overall, the role of stereotypies remains complex and context-dependent.Stereotypies are repetitive, invariant behaviors with no obvious goal or function, often observed in captive animals, mentally ill or handicapped humans, and subjects given stimulant drugs. They are considered abnormal but may result from normal behavioral processes. Stereotypies are often linked to sub-optimal environments and are used as welfare indicators. While some hypothesize they have beneficial consequences that reinforce their performance, other factors like positive feedback may explain their persistence. Empirical evidence suggests they may lower awareness of external events and reduce arousal and distress, though the causal relationship remains uncertain. Stereotypies vary in origin, causation, and characteristics, and can change over time. Stereotypies resemble normal behaviors in being invariant and resistant to change, and can become independent of their original stimuli. They may develop in animals facing insoluble problems or due to brain damage, psychiatric conditions, or drugs like amphetamine. Stereotypies are diverse, varying by species, eliciting situations, and individual differences. Examples include rocking movements in humans, bar-chewing in sows, head-swinging in bears, and pacing in foxes. Stereotypies are often seen in environments that seem sub-optimal, associated with lack of stimulation, stress, or frustration. They may result from past challenges or environmental factors, and some may involve self-damage. Stereotypies can be reinforced by providing alternative behaviors or reducing arousal, but their persistence may also be due to other factors like sensory input or endogenous opioids. While some evidence suggests stereotypies may have a coping function, others indicate they may not always be beneficial. The data is often correlational, making it difficult to determine causation. Stereotypies may be symptoms rather than causes, and their effectiveness as a coping response depends on the individual and context. Overall, the role of stereotypies remains complex and context-dependent.