An analysis of the learning deficit following hyoscine administration to man.

1. Twelve volunteer subjects completed a free-recall word learning test, a number-colour association test, and a scanning task after the following treatments: saline 1 ml, hyoscine 0.4 mg, or atropine 0.6 mg, administered by intravenous injection.2. Performance on all three tests was not significantly impaired after atropine.3. Performance on the two learning tests but not on the scanning task, was significantly impaired after hyoscine.4. Analysis of the results of the free-recall word learning test indicates that impairment of learning following hyoscine does not affect recall over intervals of a few seconds, but affects that portion of the learning curve which has been attributed to long-term (or secondary) rather than short-term (or primary) memory.5. The results suggest that hyoscine 0.4 mg may impair learning processes, without significantly depressing other psychological functions, and that the impairment of learning following hyposcine does not affect recall over intervals memory.