A controlled study found that amphetamine given before viewing pictures strengthened later memory for emotional scenes, while neutral-picture memory did not significantly change. This selective result should not be described as a universal improvement in memory.
Ballard, Gallo and de Wit studied healthy volunteers in two groups of 25. One group received placebo and 10- and 20-mg dextroamphetamine conditions. The other received placebo and 7.5- and 15-mg THC conditions. Participants viewed positive, neutral and negative pictures after dosing.
Memory was tested two days later without drug administration. The drugs were tested in separate participant groups; the study did not examine an amphetamine–THC combination.
Amphetamine improved memory for emotional pictures relative to placebo, whereas THC impaired it. Neither drug significantly affected memory for unemotional pictures. The study did not find a positive-memory bias with either drug.
Remembering emotional material more strongly and selectively favoring positive material are different propositions. The first can occur without the second, as this experiment illustrates.
The administered drugs were present during learning, while the later test occurred drug-free. The result therefore concerns effects on memory formation under this timing arrangement. It should not be used to predict what happens when a drug is taken only while retrieving an established memory.
The study also did not show that the memory effects were directly explained by subjective or physiological responses alone. Feeling stimulated is not itself a memory-accuracy measurement.
Standardized pictures and recognition testing differ from complex autobiographical events, prolonged exposure and real-world testimony. The healthy samples and selected doses constrain generalization, and the between-group drug comparison is not equivalent to testing both drugs in each person.
The findings support carefully specifying drug, emotional content and timing. They do not determine whether one person’s recollection is accurate or establish a rule for judging credibility from a toxicology result.
Related reading: Memory for future intentions.