Practice Reduced Marijuana-Related Reaction-Time Slowing Without Eliminating Other Drug Responses

A 1976 human study found less reaction-time slowing after task practice, even though physiological and subjective marijuana responses showed only slight reduction. Improved task performance did not establish disappearance of all drug effects.

The groups practiced in different states

One group first performed the complex reaction-time task during marijuana intoxication across several sessions. Another practiced drug-free before a later marijuana session. The design compared task familiarity with repeated drug-state experience rather than simply classifying people by years of use.

The strongest slowing appeared with an unfamiliar task

Participants without prior drug-free practice showed significant slowing initially and improved rapidly. The practiced group showed no detected slowing on its later intoxicated session. The authors proposed an early attention-demanding phase and a later, more automatic phase that was more resistant to the drug.

Other responses did not show comparable recovery

Pulse, salivary flow and subjective measures showed only slight reductions in acute effects across repeated use. Consequently, a normal practiced-task score cannot be treated as proof that a person is no longer intoxicated or unaffected in an unfamiliar situation.

The experiment is especially relevant when interpreting repeated performance testing. Practice can change what the task measures and how sensitive it is to drug effects. The study does not establish on-road driving safety or show that rehearsing one activity removes impairment across different demands.

Related: interpreting cannabis tolerance claims.

Research cited

Peeke SC; Jones RT; Stone GC. Effects of practice on marijuana-induced changes in reaction time. Psychopharmacology (1976). doi:10.1007/BF00423255. Findings discussed from the study abstract.