For example, imagine plunging your hands into the snow to make a snowman. Even if you put your whole hand into the snow, your fingers feel noticeably colder than your wrists. Although our environment impacts our body’s temperature, your fingers aren’t just ‘measuring’ the temperature of the snow, they are actually reflecting what is happening inside your body as blood flow changes uniquely from your fingers, wrist, and other parts of your shell so your body can maintain your core temperature.
To confirm that finger temperature captures unique physiological changes, the team analyzed the difference between iButton sensors on the finger as well as an ‘environmental sensor’ that traveled with participants to measure the world around them as they went about their days.
Results show that while the Oura Ring and finger iButton match 92% (r²=0.92), temperature information from the finger is uncorrelated to the environmental temperature; 0.1% (r²=0.001).