The effects of alcohol and caffeine on concentration test performance.

Within a 2 x 2 x 2 factorial design using two treatment factors, alcohol vs. placebo and caffeine vs. placebo, with stratification for sex as a non-treatment factor in 2 x 2 x 2 groups of 7 students each, concentration test performance was measured by an arithmetic test. The interesting result was a second-order interaction between the three factors: alcohol as well as caffeine decreased concentration in males; combined treatment performance was interpreted synergistically. For females, alcohol as well as caffeine increased concentration while the combination of both had an antagonistic effect.