Do We Control Our Decisions?
We would like to believe that we make decisions by accumulating evidence about our options and then – prudently – we choose. Comforting thought; not so accurate. A brand new study demonstrated that arousal is a powerful player in perceptual decision making.
The researchers measured pupil size, a highly sensitive index of arousal, while 26 human subjects performed a motion-discrimination task – looking at a cloud of dots and deciding in which direction the dots were moving. This was designed to mimic the types of perceptual decisions we make in everyday life. Psychologists computed their results and found that pupil size was related to decisions. Increased pupil size, reflecting heightened arousal, indicated that the person would perform WORSE.
These findings provide a uniquely clear account of how arousal state impacts decision making. Pupil size is a measure of a person’s arousal: the more aroused they are feeling, the wider their pupils are and the worse they perform on the test.
When people’s arousal levels are low they are bored and when they are too high, they can’t concentrate. People who tend to be consistently aroused were the least consistent in the decisions they made.
Dr. Peter Murphy, who led the research, said, “We are constantly required to make decisions about the world we live in. In this study, we show that how precise and reliable a person is in making a straightforward decision about motion can be predicted by simply measuring their pupil size.”
Source: Murphy PR, Vandekerckhove J, Nieuwenhuis S (2014) Pupil-Linked Arousal Determines Variability in Perceptual Decision Making. PLoS Comput Biol 10(9): e1003854. doi:10.1371/journal.pcbi.1003854. Published: September 18, 2014