This study assessed whether it was easier to generate positive and negative thoughts in either an upright or slumped position. Twenty-four participants, who reported no clinical depression or anxiety, completed the Tellegen absorption questionnaire and a self-assessment of imagery ability. Surface electromyography (sEMG) of zygomaticus major, heart rate, and respiratory rate were assessed across four 1-min counterbalanced conditions of either upright or slumped posture and either positive or negative thought generation. Posttrial checks of compliance were completed. At the end of the study, participants rated which thought was easiest to generate in the two postures. Significantly more participants (22), or 92%, indicated it was easiest to generate positive thoughts in the upright position. ANOVA of sEMG activity significantly distinguished positive and negative thoughts in both positions. Significant correlation coefficients were observed between scores on the Tellegen scale of absorption and the ability to generate thoughts quickly and between self-perceptions of imagery ability with the maintenance of thoughts across time. This study supports the finding that positive thoughts are more easily recalled in the upright posture.