ORIGINAL ARTICLE A role for recency of response conflict in producing the bivalency effect John G. Grundy • Judith M. Shedden Received: 9 July 2013 / Accepted: 7 October 2013 / Published online: 22 October 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract The bivalency effect is a block-wise response slowing that is observed during task-switching when rare stimuli that cue two tasks (bivalent stimuli) are encoun- tered. This adjustment in response style affects all trials that follow bivalent stimuli, including those trials that do not share any features with bivalent stimuli. However, the specific stimulus and response properties that trigger the bivalency effect are not well understood. In typical biva- lency effect experiments, bivalent stimuli can be congruent or incongruent with respect to the response afforded by the irrelevant stimulus feature, and this distinction has never been examined. In the present study, we show that cogni- tive load defined by the response incongruence on bivalent trials plays a critical role in producing the subsequent response slowing observed in the bivalency effect, as well as maintaining the magnitude of the bivalency effect across practice. We propose that the bivalency effect reflects a process involved in predicting future cognitive load based on recent cognitive load experience. This is in line with a recent proposal for a role of the ACC in monitoring ongoing changes in the environment to optimize future performance (Sheth et al., in Nature 488:218–221, 2012). Introduction Imagine driving through the city, stopping at a number of red stop signs, changing lanes, and staying vigilant to pedestrian encounters. If along the way you encounter a red sign indicating directions to a nearby hotel, the red colour may trigger retrieval of cognitive processes that were active in response to the recently encountered stop sign. The hotel sign acts as a bivalent stimulus because it cues two tasks. In response to bivalent stimuli, people change their response strategies such that all subsequent tasks are slowed, even when these tasks do not share features with bivalent stimuli (Grundy et al., 2013; Meier, Woodward, Rey-Mermet, & Graf, 2009; Rey-Mermet & Meier, 2012a, b; Woodward, Meier, Tipper, & Graf, 2003; Woodward, Metzak, Meier, & Holroyd, 2008). Extending the above analogy, for a period of time following the red hotel sign, responses may be slower to change lanes, stop at stop signs, and modify behaviour in response to pedestrian activity. To observe this behaviour in the laboratory, participants typically alternate predictably between three simple clas- sification tasks such as a case task (lowercase vs. uppercase letters), a parity task (odd vs. even digits), and a colour task (blue shapes vs. red shapes) by pressing a left or a right response key (e.g. left = lowercase letters, odd digits, and blue shapes; right = uppercase letters, even digits, and red shapes). After sufficient practice with univalent stimuli (stimuli that cue a single task), participants are presented with a block of trials which contain occasional bivalent stimuli (e.g. the colour on a case judgment trial is red or blue). The colour of the letter is irrelevant to the case judgment task; however, it is difficult to ignore and has a significant effect on behaviour. Responses to all subsequent univalent trials within this bivalent block are delayed rel- ative to trials in purely univalent blocks. This block-wise response slowing is known as the bivalency effect (Woodward et al., 2003). The bivalency effect is a robust and long lasting effect (Meier et al., 2009; Rey-Mermet & Meier, 2012b) believed to involve a change in response J. G. Grundy (&) Á J. M. Shedden Department of Psychology, Neuroscience and Behaviour, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada e-mail: jggrundy@gmail.com 123 Psychological Research (2014) 78:679–691 DOI 10.1007/s00426-013-0520-x