The following measures were collected during baseline and the TSST: electrocardiography (ECG, Biopac, Goleta, CA), impedance cardiography (NICO, Biopac, Goleta, CA), and blood pressure (Colin Prodigy II, Colin Medical Instruments, San Antonio, TX). Signals were integrated with Biopac MP100 hardware. Electrocardiograph and impedance cardiograph signals were scored off-line by trained personnel. Signals were visually examined and the ensembled averages were analyzed using Mindware software (Mindware Technologies, Gahanna, OH). Reactivity scores were computed by subtracting scores taken during the final minute of baseline (the “most relaxed” portion) from those collected during the first minute of the speech (the “most reactive” portion). We focused on two measures that provide the best distinction between challenge and threat states: cardiac output (CO) and total peripheral resistance (TPR). CO is the amount of blood ejected from the heart during one minute and is calculated by first estimating stroke volume (the amount of blood ejected during each beat) and multiplying that by heart rate. Increases in CO index improved cardiac efficiency. TPR is a measure of overall vasoconstriction/vasodilation. During threat states, the peripheral vasculature constricts so as to limit blood flow to the periphery. TPR was calculated with the following formula: (mean arterial pressure / CO) × 80 (Sherwood, Allen, Fahrenberg, Kelsey, Lovallo, & van Dooren et al., 1990 (link)).