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Abstract: The pure tone delayed avoidance response in the shuttle box wasestablished in six monkeys. The animal discriminated between two kinds ofstimuli (Macaca mulatta) each stimulus consisting of two pure tone pipes(1,000 Hz or 600 Hz) which were seperated by a short interval. If the twotone pipes of a given stimulus are identical in frequency, the stimulus isnegative. If the two signals are different in frequency, the stimulus is positive,and the animal should cross over to the other side. Since neither pipe signal ismore associated with punishment than the other, the correct response ispossible only when the animal retains the trace of the first signal up to thepresence of the second signal so that comparison can be made between the two. In general, animal can perform satisfactorily after a delayed period of 9seconds,the longest delayed period is 15 seconds. It took 28 experimental daysto attain the criterion of a learned delayed response on the average. Intravenous injection of LSD in doses of 30-40 μg/kg will decrease thepercentage of correct responses as compared with the criterion level, (from80％ correct response to 10％-70％). However, it will reture to normal lerelafter 24 hours.

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