Electrodermal Measures of Face Recognition Iowa State University of Science and Technology Alison L. MorrisDanielle R. Mitchell Nichole Stubbe Anne M. Cleary Background Repetition of a stimulus, as when it appears on a study list and then again on a test list, has been shown to produce reduced neural activity associated with that stimulus (e.g., Brown & Aggleton, 2001). Novel items tend to produce greater neural activity and thus more effectively increase arousal and recruit attentional resources. Electrodermal activity One indicator of autonomic arousal is the “skin conductance response” (SCR), which refers to changes in skin conductance occurring 1-3 seconds after the appearance of a discrete stimulus (see figure below). Reduced latency and/or increased amplitude of the SCR correlates positively with novelty, intensity, or significance of a stimulus. Electrodermal indicators of recognition memory Morris, Cleary, and Still (2005), using a study-test paradigm with words flashed briefly at test, found shorter SCR latencies to the nonstudied words compared to the studied words. This latency difference is consistent with the idea that novel or less recently encountered stimuli produce more rapid attentional orienting than recently encountered stimuli. Electrodermal activity and familiarity for faces Several studies have found larger phasic SCRs to familiar than to unfamiliar faces (e.g. Herzmann, Schweinberger, Sommer, & Jentzsch, 2004; Shearer & Mikulka, 1996; Tranel, Fowles, & Damasio, 1985). In these studies, familiarity implies much more than simply a prior encounter with the stimulus; highly familiar faces are associated with substantial semantic/affective information. Therefore, novelty vs. familiarity cannot be randomly assigned. In the present study, all faces were unfamiliar prior to the start of the experiment. Half of the faces were presented in a study phase (counterbalanced across participants). This enabled us to examine the electrodermal correlates of novelty separately from the effects of prior semantic/affective information.Questions: 1. Do novel faces produce shorter SCR latencies than studied faces? 2. Do faces that have been encountered only once produce larger SCRs than novel faces? 3. Do SCRs discriminate between studied faces that are “remembered” vs. merely “familiar”? Procedure Participants studied a series of unfamiliar faces, each paired with a name, for 5 seconds (requiring participants to associate a face with a name has been shown to increase the frequency of phasic SCRs to faces). At test, studied faces were randomly intermixed with novel faces. Assignment of faces to studied vs. novel conditions was counterbalanced across participants. Participants responded to each test face with “remember”, “familiar” or “new”. Next, participants decided which of two names, presented directly below the face, matched the corresponding face. Skin conductance was monitored throughout testing.Results Percentages of Responses in Each Category Accuracy Data SCR Latency SCR latencies were significantly shorter for novel faces than for studied faces, t(31) = 2.352, p <.05,  2 =.15 Thus, the latency difference between nonstudied and studied words (Morris et al., 2005) was replicated using novel and studied faces. SCR Magnitude Magnitude of SCR was significantly greater for studied than for novel faces, t(31) = 2.266, p <.05,  2 =.14 Remember vs. Familiar Responses Correct “Remember” responses were associated with a higher rate of SCRs than correct “Familiar” responses, t(31) = 2.166, p <.05,  2 =.13 Conclusions 1. Do novel faces produce shorter SCR latencies than studied faces? YES. These results replicate the similar finding from Morris et al. (2005) using words. 2. Do faces that have been encountered only once produce larger SCRs than novel faces? YES. SCR magnitude was greater for studied than for novel faces. 3. Do SCRs discriminate between studied faces that are “remembered” vs. merely “familiar”? YES. Correct “Remember” responses were more often associated with SCRs than were correct “Familiar” responses. References Brown, M. W., & Aggleton, J. P. (2001). Recognition memory: What are the roles of perirhinal cortex and hippocampus? Nature Reviews Neuroscience 2, Herzmann, G., Schweinberger, S. R., Sommer, W., & Jentzsch, I. (2004). What’s special about personally familiar faces? A multimodal approach. Psychophysiology, 41, Morris, A. L., Cleary, A. M., & Still, M. L.(2005). Electrodermal recognition without identification: A relation between the autonomic response and familiarity-based recognition? Poster presented at the Annual Meeting of the Cognitive Neuroscience Society, New York, NY. Shearer, D., & Mikulka, P. (1996). Effect of facial familiarity and task requirement on electrodermal activity. The American Journal of Psychology, 109, Tranel, D., Fowles, D.C., & Damasio, A.R. (1985). Electrodermal discrimination of familiar and unfamiliar faces: A methodology. Psychophysiology, 22 (4), ms blank Name Display Jessica Face Display 500 ms blank 500 ms tone 1000 ms blank Jessica Amanda Remember Familiar New Studied Novel HitsFalse Alarmsd Prime