MENTAL STRESS TESTING Mental Stress Testing will be used to study what happens to heart rate, blood pressure, heart rhythm, and blood vessels in arms and hands when participants are in a stressful situation. It will take up to 3 hours to complete all the procedures in the mental stress testing including the following specific procedures: In Mental Stress Tasks, different types of stress testing, including a speech task over a situation that made participants upset or angry, and/or a math test involving adding or subtracting numbers under a specific constraint, and/or a memory test, will be administered to study the effect of stress on heart; In Heart Rate Variability (HRV), participants will be asked to wear a Holter monitor that measures heart rate and rhythm for approximately 24 hours; In Cold Pressor Testing, participants' heart rate, blood pressure, heart rhythm, and blood vessels will be monitored; In Peripheral Arterial Tonometry (PAT), a blood pressure cuff will be placed on one arm and probes will be placed on participants' fingers. The probes and cuff are attached to a monitoring device that transfers a waveform graph of participants' pulse. Then the blood pressure cuff will be inflated for 5 minutes. At the end of the 5-minute period, the blood pressure cuff will be deflated to get the final tracings.