Electrodermal Measures of Face Recognition Iowa State University of Science and Technology

Alison L. Morris Danielle R. Mitchell Nichole Stubbe Anne M. Cleary

BackgroundBackground Repetition of a stimulus, as when it appears on a study list and thenagain on a test list, has been shown to produce reduced neural activityassociated with that stimulus (e.g., Brown & Aggleton, 2001). Novel items tend to produce greater neural activity and thus more effectivelyincrease 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 1-3seconds 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 wordsflashed 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 theelectrodermal correlates of novelty separately from the effects of prior semantic/affective information.

Questions: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 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.

ResultsResults 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 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.

ReferencesReferencesBrown, M. W., & Aggleton, J. P. (2001). Recognition memory: What are the roles of perirhinal cortex and hippocampus? Nature Reviews Neuroscience 2, 51-61.Herzmann, G., Schweinberger, S. R., Sommer, W., & Jentzsch, I. (2004). What’s special about personally familiar faces? A multimodal approach. Psychophysiology, 41, 688-701. 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, 131.137.Tranel, D., Fowles, D.C., & Damasio, A.R. (1985). Electrodermal discrimination of familiar and unfamiliar faces: A methodology. Psychophysiology, 22 (4), 403-408.

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Name Display

Jessica

Face Display

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Jessica Amanda

SCR Latency

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Studied Novel

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SCR Magnitude

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SCR Frequency per Response Category (Studied Faces)

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Remember Familiar

Remember Familiar New

Studied 66 19 15

Novel 4 19 77

Hits False Alarms d Prime

84 23 1.96