Differential effects of caffeine on free recall after semantic and rhyming tasks in high and low impulsives.

The effects of caffeine on free recall after acquisition on semantic and rhyming tasks were examined. Following a between-subjects design, high and low impulsive male postgraduate students were administered placebo and four doses of caffeine citrate (1, 2, 3 and 4 mg/kg body weight) in a laboratory situation. A double blind procedure was adopted for drug administration. The study supports the following conclusions: (1) under no drug condition, high impulsives recall more after semantic acquisition while their counterparts, the low impulsives, recall more after rhyming acquisition; (2) caffeine facilitates recall in high impulsives after rhyming acquisition but hinders it after semantic acquisition; (3) caffeine does not reliably influence recall of low impulsives.