Valence-dependent modulation of psychophysiological measures: Is there consistency across repeated testing? RACHEL MANBER, a JOHN J. B. ALLEN, b KEITH BURTON, b and ALFRED W. KASZNIAK b a Department of Psychiatry, University of Arizona, Tucson, USA b Department of Psychology, University of Arizona, Tucson, USA Abstract The present study used the picture perception paradigm to examine the extent to which three well-documented psychophysiological measures demonstrate consistency across time in response to emotional stimuli. The three mea- sures were the eye-blink startle response and the activation in two facial muscle regions ~zygomatic and corrugator!. Twenty-seven young women were assessed on two occasions, 2 weeks apart. Whereas activation in the corrugator and zygomatic muscle regions demonstrated the predicted patterns at both assessments ~with some attenuation in the zygomatic muscle regions!, the startle response had limited consistency across the two assessments. The startle response revealed the predicted linear pattern of valence modulation during the first assessment. During the second assessment, startle magnitude response was a quadratic function of valence ratings and a linear function of arousal ratings. The unexpected pattern of startle response during the second session appeared to be related to the content of the pleasant slides, with action slides generating quadratic valence modulation and erotic slides continuing to exhibit the expected linear valence modulation. Descriptors: Startle response, Facial muscle response, Repeated testing, Valence modulation, Arousal modulation The picture perception methodology, based on the International Affective Picture System ~ IAPS! picture set ~ Lang, Öhman, & Vaitl, 1988!, has been used extensively to study emotional percep- tion and the psychophysiology of emotion. Three psychophysio- logical measures of emotion have been shown repeatedly to be modulated by the emotional valence of the IAPS picture stimuli. These three measures are: zygomatic activation, corrugator acti- vation, and startle eye-blink response to acoustic startle ~orbicu- laris activation!. No study, however, has examined the consistency of these measures under repeated assessments. The present study, therefore, examined the degree to which the expected valence- modulated pattern of activation in each of these measures is pre- served in a repeated-measures paradigm. Two important dimensions of emotional processing, valence and arousal, have been studied using the picture perception meth- odology. Lang, Bradley, and Cuthbert ~1990! proposed that these two orthogonal dimensions of emotions represent two dimensions of “action dispositions.” Valence indicates the direction of the action in response to a stimulus or situation. According to Lang et al., affects with positive valence are associated with approach ~appetitive! behaviors, whereas affects with negative valence are associated with avoidance ~aggressive 0defensive! behaviors. The arousal associated with a given emotion indicates the amount of energy the organism allocates to the activation response. Whereas some psychophysiological measures such as skin conductance and heart rate are sensitive primarily to the general arousal associated with emotions, facial electromyography and the startle probe re- sponse 1 are sensitive primarily to the valence of the emotional response induced by the stimuli. Research has demonstrated repeatedly that the magnitude of the startle eye-blink response to a sudden intense acoustic probe is modulated by emotional valence induced by foreground stimuli, with highest activation present in response to unpleasant stimuli, lowest activation in response to pleasant stimuli, and intermediate response to neutral stimuli ~for overview see Lang et al., 1990!. Research has also shown that the activation in the zygomatic mus- cle is increased in the presence of stimuli that induce emotions with a positive valence, and that the activation in the corrugator muscle is increased in response to stimuli that induce emotions with a negative valence ~Cacioppo, Tassinary, & Fridlund, 1990; Lang, Greenwald, Bradley, & Hamm, 1993!. In addition to the consistent finding that the picture perception paradigm produces predicted valence-modulated patterns of psy- chophysiological activity in unselected samples, there exist indi- vidual differences in these patterns of activation. For example, gender differences were observed with greater zygomatic response Portions of the present data were presented at the Annual Meeting of the Society for Psychophysiological Research, Vancouver BC, Canada, October 1996. We thank Christopher Patrick for helping us think through alternative interpretations of the results. Address preprint requests to: Rachel Manber, Department of Psychiatry and Behavioral Sciences, Stanford University, 401 Quarry Road, Suite 3301, Stanford, CA 94305, USA. E-mail: rmanber@stanford.edu. 1 The modulation of the startle response to an acoustic probe depends on the timing of the acoustic probe relative to slides onset. Response to earlier probes is modulated by attention 0arousal and response to a later probe is modulated primarily by valence. Psychophysiology, 37 ~2000!, 683–692. Cambridge University Press. Printed in the USA. Copyright © 2000 Society for Psychophysiological Research 683