Testing was conducted over a 2-day period, each lasting 4-6 hours (Fig 1). Informed consent and inclusion/exclusion screening were conducted on the first day, followed by a brief semi-structured interview about the meaning of pain (data presented elsewhere). On one of the testing days (referred to here as Pain Sensitivity Day) the following tests were administered: cool and warm thresholds, heat pain threshold/tolerance, mechanical pressure pain threshold, stimulus-response to heat, temporal summation of heat pain, cold pressor pain threshold/tolerance, and ischemia pain threshold/tolerance. On the other testing day (referred to here as Pain Modulation Day) the following tests were administered: NFR threshold, Pain30 threshold (if necessary), temporal summation of NFR threshold, 52°C heat pulse series, single electric stimulations, temporal summation of NFR and electric pain, sham CPM (no conditioning stimulus presented, see description below), CPM (which includes 2-min 10°C cold water conditioning stimulus), and emotional controls of nociception (ECON; data not presented). Order of testing day was counterbalanced, blocking for race and sex. Moreover, tests within each day were partly randomized (see Fig 1). Breaks were provided between tasks to minimize carryover. Several questionnaires were administered on each testing day at the beginning and during breaks to assess background characteristics and control variables.