Marijuana: effects on free recall and subjective organization of pictures and words.

The free recall of pictures and words was compared following the administration of marijuana or placebo in a multitrial free recall task. Since pictures are thought to be registered in both visual and verbal memory stores with this encoding being mediated by some form of mental imagery, it was predicted that marijuana would produce a greater deficit in word recall in comparison to picture recall because the drug has been reported to facilitate imagery. A trend in the opposite direction followed intoxication; picture recall was inferior to word recall in the later stages of acquisition. Although overall recall was inferior under marijuana, no differences were found between the treatment conditions in subjective organization as determined by a variety of clustering measures. Recall performance following marijuana intoxication was positively related to level of recall performance in the placebo condition.