Signal regularity and the mindlessness model of vigilance William S. Helton 1 *, Todd D. Hollander 2 , Joel S. Warm 2 , Gerald Matthews 2 , William N. Dember 2 , Matthew Wallaart 2 , Gerald Beauchamp 2 , Raja Parasuraman 3 and Peter A. Hancock 4 1 Michigan Technological University, USA 2 University of Cincinnati, USA 3 George Mason University, USA 4 University of Central Florida, USA Robertson, Manly, Andrade, Baddeley, and Yiend (1997) have proposed that detection failures in vigilance tasks result from a ‘mindless’ withdrawal of attentional effort from the monitoring assignment. To explore that view, they modified the traditional vigilance task, in which observers make button-press responses to signify the detection of rarely occurring critical signals, to one in which button-press responses acknowledge frequently occurring non-signal events and response withholding signifies signal detection. This modification is designed to promote a mindless withdrawal of attentional effort from the task through routinization. The present study challenges the validity of the mindlessness model by showing that with both types of task, observers utilize subtle patterns in the temporal structure of critical signal appearances to develop expectations about the time course of those appearances that affect performance efficiency. Such expectations enhance performance on the traditional vigilance task, but degrade performance on the modified task. Vigilance or sustained attention tasks typically require observers to monitor displays over extended periods, and to execute overt detection responses to the appearance of low probability critical signals. The signals are usually clearly perceivable when observers are alerted to them but are not compelling changes in the observers’ operating environment. In addition, the signals are usually embedded in a context of recurrent non-signal (neutral) events, which, unlike signals, require no overt response from observers (Davies & Parasuraman, 1982; Warm, 1984; Warm & Jerison, 1984). Vigilance tasks and the processes that influence their performance are of interest because of the insights they provide into the factors that control attention (Broadbent, * Correspondence should be addressed to Dr William Helton, Department of Psychology, Michigan Technological University, Houghton, MI 499312, USA (e-mail: deak_helton@yahoo.com). The British Psychological Society 249 British Journal of Psychology (2005), 96, 249–261 q 2005 The British Psychological Society www.bpsjournals.co.uk DOI:10.1348/000712605X38369