Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
The effect appears strongest at night. Data points represent mean values of the raw data across all individuals (n = 17). Error bars represent one standard error of the mean.
