Weather and light can affect our moods, but a study has revealed that amount of light that falls on the Earth's surface also influences our spending behaviour.
According to researchers, on the days with higher light intensity, people made worse decisions and they were more inconsistent in the choices that they made.
A study of more than 2,500 people provides new evidence about the effects of luminance on the quality and consistency of our financial decision-making.
Luminance is a measurement of the amount of light that falls on the Earth's surface, which can be affected by cloud cover, humidity, suspended particles and time of day and year.
Researchers already know luminance affects behaviour, with sensors in the human retina carrying continuous information on light levels to the hypothalamus, a section of the brain which regulates functions such as hunger, sleep and sex drive.
Study author Agnieszka Tymula from the University of Sydney adds to existing knowledge by investigating how luminance affected 2,530 people's decisions about monetary gambles.
When the luminance level was high, people were more likely to avoid known risks. When offered a choice between a certain $5 payout and a 50 percent chance of $20, they were more likely to go for the certain $5.
Surprisingly, they had greater tolerance for unknown risks.
Tymula with Professor Paul Glimcher from New York University asked people to make 40 monetary decisions, using touch screens mounted at an exhibition on ageing at the National Academy of Science Museum in Washington D.C.
In each situation, people could choose a certain payout of $5, or a lottery option with the possibility of receiving nothing, or a cash amount between $5 and $125.
They found that luminance affects decision-making in different ways, with higher and lower levels of light intensity.
On high luminance days, they were more likely to go for an unknown chance of getting $20 over the certain $5 payout.
"Overall, the effects are not of an enormous magnitude, but nevertheless they are consistent, significant and strong enough to be expected to have significant effects on financial markets," Tymula explained.