When complexity helps: an electrophysiological analysis of multiple feature bene®ts in object perception Lisa R. Fournier a, * , Marten K. Scheers b , Michael G.H. Coles b , Amy Adamson b , Enrique Vila Abad c a Department of Psychology, Washington State University, Pullman, WA 99164-4820, USA b University of Illinois at Urbana±Champaign, Illinois, USA c Universidad Nacional de Educacion a Distancia, Madrid, Spain Received 1 December 1997; received in revised form 29 November 1999; accepted 6 December 1999 Abstract Fournier, L. R., Eriksen, C. W. and Bowd, C. (1998. Multiple feature discrimination faster than single feature discrimination within the same object? Perception & Psychophysics 60, 1384±1405) found that judging the presence of multiple features within an object is faster than judging the presence of the least discriminable of these features alone (multiple feature ben- e®ts, MFBs). When an `absent' response is required, responses are slower when some of the relevant (target) features are present (multiple feature costs, MFCs). The present study utilized psychophysiological measures (of the event-related brain potential and the electromyogram) to determine the contributions of response priming and stimulus evaluation processes (P300 latency) to these eects. P300 latency and reaction time (RT) both showed evidence of MFBs and MFCs. These ®ndings suggest that MFBs and MFCs can be attributed to processing that occurs prior to response selection. No dissociations between P300 latency and RT measures were found for `present' responses across the single and multiple feature judgements. How- ever, for `absent' responses, partial dissociations were found between these measures, and partial errors and longer response execution intervals were observed more often when an object contained some target features. These ®ndings suggest that response priming contrib- utes to MFCs, but may not contribute to MFBs. Ó 2000 Elsevier Science B.V. All rights reserved. Acta Psychologica 104 (2000) 119±142 www.elsevier.com/locate/actpsy * Corresponding author. Tel.: +1-509-335-4415; fax: +1-509-335-5043. E-mail address: fournier@wsunix.wsu.edu (L.R. Fournier). 0001-6918/00/$ - see front matter Ó 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 0 1 - 6 9 1 8 ( 0 0 ) 0 0 0 1 4 - 7