A linear relationship was found between judgements given by 160 subjects to 7 objects presented as single stimuli (alpha judgements) and judgements given to the same objects presented with a condition (gamma judgements). This relationship holds for alpha judgements and the gamma judgements that belong to a family of constant stimulus and varying conditions (CSF). The corresponding regression coefficient, operating as a multiplicator, estimates the contrast effect, i.e. it measures the degree in which the stimulus is dependent of the conditions. The independence of certain stimuli allowed to isolate an additive effect (called K) in the subjects' gamma estimations. The elimination of effect K maximized the exactness of the prediction of the gamma judgements from the conditional distribution of the alpha judgements. (Author/RC)