0362-1197/05/3106- © 2005 MAIK “Nauka /Interperiodica” 0646 Human Physiology, Vol. 31, No. 6, 2005, pp. 646–650. From Fiziologiya Cheloveka, Vol. 31, No. 6, 2005, pp. 32–36. Original English Text Copyright © 2005 by Tressoldi, Martinelli, Massaccesi, Sartori. 1 Cognitive activity induces changes not only at the cortical level but also at the peripheral (cardiac, skin conductance, etc.) level. This relationship is firmly established not only for cognitive tasks involving emo- tional stimuli [1–3] but also even if tasks are emotion- free. Research on the relationship between neuropsy- chophysiological variables and cognitive tasks has a relatively long tradition. Regarding heart rate, the psy- chophysiological variable used in the present investiga- tion, we can recall the pioneering contribution of Gra- ham and Clifton [4] investigating the change in heart rate as a component of the orienting response, followed by the investigation by many other authors of different aspects of cognition such as attention [5], stimulus sig- nificance [6], self-induced thoughts [7], goal difficulty [8], and so on. Among cognitive tasks, those requiring intuition are far less investigated. The notion of intuition varies among authors and fields of investigation such as psy- chology, neuroscience, and philosophy. The definition we will adopt is “knowing without being able to explain how we know” [9, 10]. Baylor [11] describes intuitive thinking as a cognitive activity proceeding automati- cally, interpreting immediately the situation it is facing. Stanovich and West [12] labeled the cognitive pro- cesses of intuition and reasoning as System 1 and Sys- tem 2. The operations of System 1 are fast, automatic, effortless, associative, and difficult to control or mod- ify. The operations of System 2, on the contrary, are slower, serial, effortful, and deliberately controlled. Intuitive cognitive activity is not episodic but is proba- bly the cognitive process most frequently used in real 1 This article was submitted by the authors in English. life when it is necessary to solve social, economic, or practical problematic situations with time pressure. Although it is relevant, the scientific research on intu- ition is not very rich in either the cognitive or the neu- rophysiological field. It is worth mentioning the review by Lieberman [13], who proposes a link between implicit learning and social cognition, suggesting a common neural substrate, but empirical investigations remain lacking. The present investigation took its inspiration from the findings and methodology of Bechara et al. [14, 15]. These authors revealed that skin resistance varied according to a positive or negative decision in a gam- bling task, well before subjects could discover and explain the rule governing the payoff. Research has shown that gamblers exhibit increases in physiological arousal, heart rate included, when par- ticipating or even imagining that they are participating in gambling [16–18]. The possibility that physiological responses can convey information before subjects experience con- scious awareness is an interesting line of investigation. With a first exploratory experiment followed by a confirmatory one, we aimed at exploring the possibility that heart rate responses differ according to the cate- gory of the targets before subjects consciously possess this information. In contrast to Bechara et al. [14, 15], who used a gambling task with an underlying rule, we devised a simple game whose solution required “pure” intuition, that is, a decision that could not rely on implicit learning or personal expertise. To prevent any possibility of discovery of the rule underlying the task, the targets were chosen by an automated random algo- Heart Rate Differences between Targets and Nontargets in Intuitive Tasks 1 P. E. Tressoldi, M. Martinelli, S. Massaccesi, and L. Sartori Department of General Psychology, University of Padua, Padua, Italy e-mail: patrizio.tressoldi@unipd.it Received March 3, 2005 Abstract—This study reports the results of one experiment and a replication, aimed at investigating heart rate changes related to a purely intuitive task. In each experiment, 12 subjects were required to guess which of four pictures presented in sequence for about 10 s was the target. Each subject performed 20 trials. In each trial, the target was automatically selected using a pseudorandom algorithm. The heart rate was recorded during the pic- ture presentation. In the first experiment, a statistically significant heart rate increment associated with targets with respect to nontargets was observed. The replication experiment with 12 new subjects confirmed the data obtained in the main experiment. These findings support the hypothesis that heart rate is related not only to con- scious but also to unconscious cognitive activity such as that involved in intuitive tasks, giving convergent evi- dence for the models describing human intuitive cognitive activity as a double, partially independent informa- tion processing system.