Numerous previous studies found monopolar rather than bipolar dimensions of affect (defined as emotion represented in language), but they may have included methodological biases against bipolarity. The present study of 150 undergraduates' self-report data on 11 affect scales showed that response format and acquiescence response style significantly shifted correlations between hypothesized opposites away from showing bipolarity. When these biases were taken into account, pleasure was the bipolar opposite of displeasure and arousal of sleepiness. In turn, pleasure-displeasure and degree of arousal formed a 2-dimensional bipolar space that accounted for almost all of the reliable variance in R. E. Thayer's (1970) 4 factors of activation plus a measure of depression. Dominance and submissiveness factors were also included in the study, but invalidity of the scales used precluded any conclusions regarding their bipolarity. (27 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1979 American Psychological Association.