Comparison of Stress and Learning Effects of Three Different ...

ii. Learned Helplessness
Another significant result of chronic stress is learned helplessness which was first defined by
OVERMAIER and SELIGMAN (1967). Learned helplessness is a situation which develops
when the animal is subjected to chronic and unavoidable stress.
OVERMAIER and SELIGMAN (1967) showed that the dog exposed to chronic unavoidable
shock, later fails to learn to escape from the shock in a different situation although escape was
possible. In this manner, that study proved that repeated unsuccessful attempts to avoid the
aversive event can result in behavioral inhibition and a state of depression.
iii. Stereotypic behavior
MASON (1991) defined stereotypic behavior as a ‘’repetitive invariant behavior pattern with
no obvious goal or function’’. LINDSAY (2001) pointed out that compulsive behaviors
usually consist of ordinary behaviors expressed out of context, in excess, or in an exaggerated
form and occur under unnatural conditions such as conflict and frustration. He further
emphasized that ‘’ stereotypes have species-specific relevance and present similar forms in
animals belonging to same species’’.
FRIEND (1991) stated that stereotypic behaviors such as tongue rolling in confined bulls or
cribbing and stall weaving in horses, seem to help animals coping with stress by increasing
their sensory stimulation, muscular and skeletal activity, and the sense of control over their
relationship to the environment. On the other hand, in some cases the stereotypic behavior
leads to undesirable effects like injury to the feed of chronically pacing animal.
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