period of one hour dark and two hours light. Other rhythm disruptions may be used, such as providing limited amounts at short intervals to avoid entrainment to average mealtimes. These modifications can show the strength and influence of the intrinsic circadian clock.

Researchers can conduct studies to measure entrainment for various organisms and the bounds of circadian cycle lengths. For example, some animals can be entrained to a 22-hour day, but not to a 20-hour day. Although previous consensus