Neuroticism-Anxiety, Impulsive-Sensation Seeking and autonomic responses to somatosensory stimuli Vilfredo De Pascalis ⁎ , Elena Valerio, Mariacaterina Santoro, Immacolata Cacace Department of Psychology, University of Rome ‘La Sapienza’, Italy Received 9 July 2005; received in revised form 24 May 2006; accepted 6 June 2006 Available online 8 August 2006 Abstract This study focused on autonomic responding in participants who scored high vs. low on the Neuroticism-Anxiety (N-Anx) and Impulsive- Sensation Seeking (Imp-SS) dimensions of the Zuckerman–Kuhlman Personality Questionnaire—Form III. Participants were presented with series of tones (standards, deviants and novels) and they received a mild electric shock (one, two or three pulses) at each 15th tone. Resting pre- stimulus skin conductance level (SCL) and heart rate (HR) level was recorded, as well as the skin conductance response (SCR) and (anticipatory) HR response to the electric stimuli. The autonomic measures differentiated between high- vs. low Imp-SS participants but failed to discriminate between high- vs. low N-Anx participants, with the exception that high N-Anx participants showed smaller SCRs on some trials compared to the low N-Anx participants. High Imp-SS had a lower pre-stimulus SCL and smaller SCRs to deviant stimuli compared to low Imp-SS participants. Additionally, their HR acceleration was smaller in anticipation of the first and the deviant tones whereas their deceleratory response was larger relative to the HR changes observed for the low Imp-SS participants. This pattern of findings was taken to suggest that high Imp-SS participants are more arousable and less prone to defensive reactions to novel or aversive stimulation. © 2006 Elsevier B.V. All rights reserved. Keywords: Impulsive-Sensation Seeking; Neuroticism-Anxiety; Skin conductance change; Heart rate change; Orienting response; Defensive response 1. Introduction Sensation seeking (SS) is a dimension of personality defined by the individual's need for sensory stimulation and the level of risk taken for the sake of such stimulation (Zuckerman, 1994). For high sensation seeking individuals, the reward of the sen- sation outweighs most punishment and they are willing to take any risk in an effort to satisfy the need for challenging expe- riences and sensations. It is believed that individual differences in arousal levels prompt individuals to avoid or seek sensation, so as to maintain an optimal level of arousal (Zuckerman et al., 1980; Kohn, 1987). Electrodermal measures have been employed widely to assess individual differences in arousal level and arousability (Malmo, 1959; Venables and Christie, 1980). Thus, skin conductance level (SCL) and skin conductance responses (SCRs) are used to provide indices of tonic and phasic arousal (e.g., Fowles, 1980; Boucsein, 1992). Studies focusing on tonic arousal, as indexed by SCL, observed a lower SCL in high SS individuals compared to low SS individuals (e.g., Gatzke-Kopp et al., 2002; Plouffe and Stelmack, 1986) supporting the notion that arousal level is lower in high SS individuals. Likewise, SRC discriminates between high and low SS individuals. The typical finding is that high SS individuals respond somewhat more vigorously to initial or novel stimulation than low SS individuals (e.g., Feij et al., 1985; Neary and Zuckerman, 1976; Robinson and Zahn, 1983; Smith et al., 1986). It should be noted, however, that several studies failed to replicate stronger SCRs in high SS individuals (e.g., Cox, 1978; Ridgeway and Hare, 1981; Zuckerman et al., 1988). Zuckerman (1990) argued that the apparent inconsistencies across studies might be due to the uni-phasic nature of SCR that does not allow differentiating between orienting vs. defensive reactions. In this regard, the bi-phasic heart rate (HR) response might qualify as a more suitable indicator of individual differ- ences in arousability. HR slowing to a stimulus is interpreted in terms of orienting whereas HR speeding is taken to suggest a International Journal of Psychophysiology 63 (2007) 16 – 24 www.elsevier.com/locate/ijpsycho ⁎ Corresponding author. Dipartimento di Psicologia, Università di Roma ‘La Sapienza’, Italy. Tel.: +39 0649917643; fax: +39 064451667. E-mail address: v.depascalis@caspur.it (V. De Pascalis). 0167-8760/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.ijpsycho.2006.06.004