A study examined the relationship between the time of day and creativity.
There were two segments of time considered in this study. These times differ from person to person.
The first time of day is the ‘optimal’ time of day. This is when a person feels most awake. In ‘non-optimal’ times of day, a person does not feel as awake.
It found that during the non-optimal time of day was better for creativity. The optimal time of day was better for solving problems that were less creative.
It may be that when a person isn’t thinking as clear that they are more creative. A certain amount of tiredness can help in finding intuitive solutions to a problem.
Mareike B. Wieth; “Time of day effects on problem solving: When the non-optimal is optimal”; Thinking & Reasoning, Volume 17, 2011 – Issue 4