Seligmanalteredthispatternbystrappingdogsinharnesses
andgivingthemshocksfrom whichtheyhad nomeansof
escape. When the dogs were then placed in the original
shuttlebox situation from which escape was possible, he
found that
suchadogreactsinitiallytoshockintheshuttleboxinthe
samemannerasthenaivedog.Howeverindramaticcontrast
tothenaivedogitsoonstopsrunningandremainssilentuntil
shock terminates. The dog does not cross the barrier and
escapefromshock.Ratheritseemsto“giveup”andpassively
“accept”theshock.Onsucceedingtrialsthedogcontinuesto
failtomakeescapemovementsandthustakes 50 secondsof
severe, pulsating shock on each trial.... A dog previously
exposedto inescapableshock...maytake unlimitedshock
without escaping or avoiding at all.^35
Inthe1980s,psychologistshavecontinuedtocarryoutthese
“learnedhelplessness”experiments.AtTempleUniversityin
Philadelphia, Philip Bersh and three other experimenters
trainedratstorecognizeawarninglightthatalertedthemtoa
shockthatwouldbedeliveredwithinfiveseconds.Oncethey
understood thewarning, therats couldavoidtheshock by
movingintothesafecompartment.Aftertheratshadlearned
thisavoidancebehavior,theexperimenterswalledoffthesafe
chamber and subjected them to prolonged periods of
inescapable shock. Predictably,
theyfoundthatevenafterescapewaspossible,theratswere
unable to relearn the escape behavior quickly.^36
Bersh and colleagues also subjected 372 rats to aversive
shock testing to try to determine the relationship between
Pavlovian conditioning and learned helplessness. They