Abstract

Amphetamine sulfate (14 mg/70 kg body weight) was given on two occasions, secobarbital sodium (50 mg/70 kg) was given on one occasion, and placebos were given twice to each of 78 male college and graduate students. All five medications were given in visually identical capsules, and on the double-blind basis. On each experimental day, a subject was given a mood and feeling check list, a 60-minute test of intermediate calculus, a 4-minute digit-letter coding test, and finally another mood and feeling check list.

The significant subjective effects of amphetamine, both at the beginning and at the end of the testing session, were numerous and were consistent with earlier findings. The subjective effects of secobarbital were mostly nonsignificant, especially at the end of the testing session. Secobarbital tended to impair performance on both the calculus and coding tests, but neither tendency was statistically significant. Amphetamine did not influence performance on the calculus test, but it did facilitate performance on the coding test. The significant effect of amphetamine on coding performance is taken as further evidence for the general usefulness of the digit-letter coding test in psychopharmacological studies using human subjects.