Inclusion Criteria:  Age: 18 to old 64 years old Self-identified African American/Black English speaking, able to provide informed consent Self-reported bedtime between 10 PM and 12 AM for 5/7 nights for the past 3-months (stability to be confirmed by actigraphy and sleep diary) Self-reported sleep duration of between 6.5 and 8.5 hours for 5/7 nights for the last month (duration to be confirmed by actigraphy and sleep diary)  Exclusion Criteria:  Aged greater than 64 years (to minimize age-related differences in sleep quantity and architecture). Body mass index of 40 or above (to exclude for obesity, which can impair physiologic recording and confound study outcomes). Presence of any clinical sleep disorder, including insomnia and obstructive sleep apnea (OSA), as assessed by validated screening measure. OSA will also be assessed objectively during the Sleep Screening period. Medical or psychiatric condition, as assessed by self-report and clinical interview, that is likely to affect sleep/wake function or cardiovascular functioning, including doctor diagnosed arrhythmia, hypertension, congestive heart failure, major depression, bipolar disorder, post-traumatic stress disorder. Medication use that is likely to affect sleep/wake function or cardiovascular functioning, including antidepressants, anxiolytic or soporific medication, and beta-blockers.