Morningness–eveningness orientation, optimal time-of-day and attitude change: Evidence for the systematic processing of a persuasive communication Pearl Y. Martin * , Shelby Marrington School of Psychology, University of Queensland, Brisbane, QLD 4072, Australia Received 28 June 2004; received in revised form 1 December 2004; accepted 31 January 2005 Available online 23 March 2005 Abstract This study investigates the effects of morningness–eveningness orientation and time-of-day on persua- sion. In an attitude change paradigm, 120 female participants read a persuasive message that consisted of six counter-attitudinal arguments (anti-voluntary euthanasia) either in the morning (8:30 a.m.) or in the evening (7:00 p.m.). Attitude change was assessed by measuring attitudes towards the target issue before and after exposure to the message. Message processing was assessed by thought-listing and message recall tasks. Self-reported mood and arousal were monitored throughout. Participants were classified into M- and E-types according to their scores on the Horne and O ¨ stberg (1976) MEQ questionnaire. When tested at their respective optimal time-of-day (i.e., morning for M-types/evening for E-types), M- and E-types reported higher energetic arousal, greater agreement with the message, greater message-congruent thinking, and a propensity for superior message recall compared to M- and E-types tested at their nonoptimal time- of-day (i.e., evening for M-types/morning for E-types). The attitude change in those tested at their optimal time-of-day was mediated by the level of message-congruent thinking. Results are interpreted in terms of the Elaboration Likelihood Model of persuasion. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Morningness–eveningness; Time-of-day; Arousal; Central-route processing; Persuasion 0191-8869/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.paid.2005.01.021 * Corresponding author. Tel.: +61 7 3365 4496; fax: +61 7 3365 4466. E-mail address: p.martin@psy.uq.edu.au (P.Y. Martin). www.elsevier.com/locate/paid Personality and Individual Differences 39 (2005) 367–377