Marijuana Effects on Semantic Memory: Verification of Common and Uncommon Category Members

Abstract

Effects of smoked marijuana containing 10 mg delta-9-tetrahydrocannabinol and placebo on retrieval of simple, real-world knowledge in semantic memory were studied. In Exp. 1, subjects (36 men, mean age 23.8 yr.) decided whether an item (e.g. apple) belonged to a specified category (e.g., fruit). In Exp. 2, subjects (40 men, mean age 22.8 yr.) decided whether two items (e.g., apple, peach) belonged to the same category. Marijuana did not alter the normal difference in reaction time between common and uncommon examples of categories, suggesting that effects of marijuana on associations do not derive directly from underlying, general alterations of semantic memory retrieval. Marijuana's effects were not influenced by the demands on memory retrieval or by providing advance information relevant to the required decisions, suggesting memory retrieval was not impaired by this dose of marijuana.