1. N=52 self-reported Christian undergraduates were recruited to the lab and told they would play a coin flipping game (i.e., Long et al., 2012) against another person on a different floor. Each subject provided a picture and filled out a few questions after which a profile was generated. They were told that if they could correctly guess 80% of the reported coin flips, they would receive $5 per profile. In reality, all profiles were actually computer generated and set to correctly report the outcome of the coin flip on 66% of trials. Design: 2 Religion (Christian vs. Muslim) by 2 Costly Signaling (Donated Time/Money vs. not). Half viewed Christian no-signal and Muslim yes-signal profiles, the other half Christian yes-signal and Muslim no-signal conditions. EEG was recorded from DC to 80Hz with a linked average mastoid reference. Time-frequency measures were computed by convolving the continuous EEG data with a set of complex Morlet wavelets. Epochs from -200 to 1500 ms from the onset of the “Sam is deciding” slide were then extracted and power was normalized by conversion to a decibel scale (10 x log10[power(t)/ power(baseline)]), allowing a direct comparison of effects across frequency bands. The baseline for each frequency consisted of the average power from –200 to 0 ms. Overall subjects probability matched and chose to trust the reported coin flips from each profile equally. References Hall DL, Cohen AB, Meyer KK, Varley AH, & Brewer GA (2015). Costly signaling increases trust, even across religious affiliations. Psychological Science, 26, 1368-1376. Long Y, Jiang X, & Zhou X (2012). To believe or not to believe: Trust choice modulates brain responses in outcome evaluation. Neuroscience, 200, 50-58. Benedek M, Schickel RJ, Jauk E, Fink A, Neubauer AC (2014). Alpha power increases in right parietal cortex reflects focused internal attention. Neuropsychologia, 56, 393-400. Generously funded by a “Religion and Trust” grant from AFOSR to ABC and GAB. Trust decisions are mediated by alpha suppression over parietal electrode sites Chris Blais, Derek Ellis, Kimberly Wingert, Adam B. Cohen, & Gene A. Brewer Methods and Procedure Results MACLab Arizona State University The Present Investigation HEAD Trust Distrust (1) (2) The real result was…+ TAIL (correct trust decision) 6 ? Sam is deciding… 2000-4000ms1000ms500msUntil response (Mean RTs=782ms) 800ms300-500ms1500ms We replicate the counterintuitive finding that costly signaling promotes trust across traditional in-group/out-group boundaries. These findings are consistent with the interpretation that subjects maintain a trust mental set for trustworthy profiles and a distrust mental set for untrustworthy profiles. Subjects appear to form an intention to trust/distrust early in the processing stream, and that this intention manifests as alpha suppression over parietal electrodes. Additional analyses are being conducted to determine how this signal changes across the time-course of the trial and allow subjects to probability match. There were two goals for this project. 1. Determine the electrophysiological correlates of making trust decisions. The limited prior studies have focused on ERPs time-locked to feedback about a trust decision (e.g., Long et al., 2012). The present study extends this work by examining the time period during which the trustor knew they had to make a decision, but before any information was presented. 2. Replicate and extend Hall et al., (2015) who reported the counterintuitive finding that donating time or money to your religious group, costly signaling, increased perceptions of trustworthiness—even across religious boundaries. To accomplish these goals, we created in-group/out-group profiles that regularly donated their time & money to causes associated with their church/mosque or not. Our main hypothesis was that there would be decreased alpha power over parietal cortex, reflecting focused internal attention (e.g., Benedek et al., 2014), for rendering trust decisions to trustworthy (i.e., a costly signaling target) and distrust decisions to untrustworthy (i.e., a non-costly signaling target) profiles compared to distrust decisions to trustworthy and trust decisions to untrustworthy profiles. There were reliable differences in the pattern of oscillatory activity in the alpha band (8-13Hz) over parietal electrode sites 1-3 s prior to their trust decision. For trustworthy profiles this manifested as greater alpha suppression for trust decisions vs. distrust decisions. For untrustworthy profiles this manifested as greater alpha suppression for distrust decisions vs. trust decisions. Critically, this differential activity (distrust – trust) predicted the number of trust decisions made as a function of costly signaling, but not for in- group/out-group status. Sam is deciding… 2000-4000ms HEAD | TAIL 1000ms ? 500ms Trust Y|N -1ms Real result was 800ms {111;114} {11;12;21;22} {32} {33} {34}{35} 300- 500ms HEAD|TAIL (correct|incorrect trust decision) 1500ms {36}{30;31;40;41} Discussion Trust Composite (M ± SEM) 0 – 500 500-1000 1000-1500 1500-2000 2000-2500 Costly Signal No Costly Signal Christian (ingroup) Muslim (outgroup) Profile Type Time Range Christian target signaling Muslim target not signaling Muslim target signaling Christian target not signaling DistrustTrustDistrust – Trust