For each subjective measure, initial and adaptive responses were calculated for both the placebo and alcohol sessions. The initial response was computed as Block 1 score – Block 0 score, so that a positive value indicated an increase from baseline, and a negative value indicated a decrease. A single, scalar adaptive index for each subjective response was derived from the data from Block 0, 1 and 2: acute adaptation = Sign(B1−B0)*(B2−B1). The Sign function allowed positive values of the index to be interpreted as acute sensitization and negative values as acute tolerance to alcohol. Then, the adaptive indices for the placebo session were subtracted from the respective adaptive indices for the alcohol session to create for each subject a placebo-adjusted adaptive response index.
