“…Although heart rate is a widely used arousal indicator, there is evidence that under some circumstances the covariation with other physiological indicators, such as skin conductance and respiration rate, seems to disappear (Taylor & Epstein, 1967). Similar findings have been reported for the correlation between heart rate and subjective arousal (Balteş, Avram, Miclea, & Miu, 2011;Bensafi, Rouby, Farget, Bertrand, Vigouroux, & Holley, 2002;Lang, Greenwald, Bradley, & Hamm, 1993;Schäfer & Sedlmeier, 2011;Van der Zwaag, Westerink, & Van den Broek, 2011). Further doubts on the reliability of heart rate as an indicator of arousal arise from studies on the conscious controllability of heart rate (Carroll & Whellock, 1980;De Pascalis, Palumbo, & Ronchitelli, 1991) and on autonomous changes of heart rate, such as the diving reflex (Folgering et al, 1983;Gooden, 1994;Ross & Steptoe, 1980;Sterba & Lundgren, 1985).…”