ENHANCING CAFFEINE REINFORCEMENT BY BEHAVIORAL REQUIREMENTS FOLLOWINGDRUG INGESTION

Each morning eight adults with caffeine versus placebo discrimination histories ingested letter-coded capsules containing 100 mg caffeine or placebo and then engaged in a relaxation or vigilance activity. Subje cts were first exposed to caffeine and placebo once each with each act ivity. Then each day for 10 days subjects made two choices; they chose which compound they would prefer if vigilance were scheduled and whic h they would prefer if relaxation were scheduled, with the restriction that they could not choose the same compound with both activities; on ly one choice (randomly selected) was reinforced. Eight of eight subje cts always chose caffeine with vigilance. The next choice condition wa s identical, except that subjects were free to take either compound wi th both activities. Six of six subjects reliably chose caffeine with v igilance. Four reliably chose placebo with relaxation. In the final co ndition, each day for 10 days subjects chose between each drug and eac h of 52 monetary values; those choices were made separately for vigila nce and relaxation; only one choice (randomly selected) was reinforced . For six of seven subjects, the maximum dollar value at which subject s chose drug over money was higher for caffeine in vigilance than for placebo in either activity. For five subjects, the maximum value at wh ich subjects chose caffeine over money was higher in vigilance than in relaxation. Overall, this study demonstrates enhanced caffeine reinfo rcement when a vigilance activity followed drug ingestion.