Evidence for effects of task difficulty but not learning on neurophysiological variables associated with effort Anne-Marie Brouwer ⁎, Maarten A. Hogervorst, Michael Holewijn, Jan B.F. van Erp TNO, P.O. Box 23, 3769 ZG Soesterberg, The Netherlands abstract article info Article history: Received 23 December 2013 Received in revised form 8 May 2014 Accepted 10 May 2014 Available online 16 May 2014 Keywords: learning effort workload physiology EEG eye Learning to master a task is expected to be accompanied by a decrease in effort during task execution. We exam- ine the possibility to monitor learning using physiological measures that have been reported to reflect effort or workload. Thirty-five participants performed different difficulty levels of the n-back task while a range of physiological and performance measurements were recorded. In order to dissociate non-specific time-related ef- fects from effects of learning, we used the easiest level as a baseline condition. This condition is expected to only reflect non-specific effects of time. Performance and subjective measures confirmed more learning for the difficult level than for the easy level. The difficulty levels affected physiological variables in the way as expected, therewith showing their sensitivity. However, while most of the physiological variables were also affected by time, time-related effects were generally the same for the easy and the difficult level. Thus, in a well-controlled experiment that enabled the dissociation of general time effects from learning we did not find physiological variables to indicate decreasing effort associated with learning. Theoretical and practical implications are discussed. © 2014 Elsevier B.V. All rights reserved. 1. Introduction We need to monitor learning for a number of reasons, such as pro- viding trainees with appropriate feedback, determining whether a trainee has learned sufficiently well and evaluating educative systems. One straightforward way to do this is to monitor behavioral perfor- mance, e.g. the time it takes to perform a task and the number of errors made. However, behavioral performance is not only determined by (learned) skills. Another important factor is mental effort, where the negative effect of lacking skills on behavioral performance can be counteracted by investing a large amount of effort. This means that while trainees may have reached the desired level of performance, they may need a large amount of effort in order to maintain this level. In such a case, additional learning may still be required in order to transform effortful, controlled cognitive processes into more automatic and efficient processes (Gopher and Kimchi, 1989; Liu and Wickens, 1994; Schneider and Fisk, 1982). Thus, information about performance and effort is needed to monitor the learning process. Information about effort could be extracted from physiological measures as discussed next. 1.1. Effort and its indicators: peripheral physiology, EEG and eye-related measures Effort, or as termed by Brehm and Self, motivational arousal, only oc- curs if a number of conditions are met (Brehm and Self, 1989). Firstly, there should be the expectation that a certain behavior will lead to cer- tain desirable outcome values (task incentive). Secondly, the required behavior should be difficult but considered to be within one's capacity and justified by the potential gain. When the required behavior is con- sidered to be too difficult, i.e. outside one's capacity or outweighing the potential gain, effort will not be invested. When the required behav- ior is easy to perform, effort will be low or absent since the organism will strive to conserve energy. A concept that is very close to mental effort is mental workload (Gaillard and Wientjes, 1994; Hockey, 1986). While the term ‘workload’ evokes associations with externally imposed task demands, workload involves internal factors such as the ability of the in- dividual to cope with these demands (Borghini et al., 2012; Gopher and Donchin, 1986; Kantowitz, 1988; O’Donnell and Eggemeier, 1986) as well as the motivation of the individual to perform the task at hand (Veltman, 2002). Thus, just like effort, workload can only be high when the task is difficult but perceived to be feasible, and leads to, and is in proportion with, rewarding outcomes. The function of effort is the production of appropriate behavior, therewith rendering measures of physiological arousal (high sympa- thetic relative to parasympathetic activation) likely candidates for measuring effort (Brehm and Self, 1989; Gawron et al., 1989; Mulder and Mulder, 1987). Changes in sympathetic and parasympathetic International Journal of Psychophysiology 93 (2014) 242–252 ⁎ Corresponding author. Tel.: +31 888665960. E-mail addresses: anne-marie.brouwer@tno.nl (A.-M. Brouwer), maarten.hogervorst@tno.nl (M.A. Hogervorst), michael.holewijn@tno.nl (M. Holewijn), jan.vanerp@tno.nl (J.B.F. van Erp). http://dx.doi.org/10.1016/j.ijpsycho.2014.05.004 0167-8760/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect International Journal of Psychophysiology journal homepage: www.elsevier.com/locate/ijpsycho