Your eyes may give your thoughts away, according to new research.
Eye movements can reflect emotional state, influence memories and provide clues about the way someone thinks, according to scientists from Arizona State University.
Researchers have long known that pupils dilate and constrict not only in response to changes in light conditions but also in response to emotional changes and arousing stimuli, but now a new study published in the journal Current Directions in Psychological Science found that pupils also dilate when the brain is creating and retrieving memories.
Scientists used pupillometry, or the study of pupil movement, to measure cognitive processes such as attention and memory and found that pupils tend to dilate as cognitive demand increases.
Lead author Stephen Goldinger said that because the neural mechanisms responsible for such "task-evoked pupillary reflexes" implicate a role for memory processes, pupillometry can be used to study individuals who are difficult to study, like amnesiacs and infants.
Another study, also published in Current Directions in Psychological Science, found that our eye movements are systematically related to our internal thought processes.
Lead author Howard Ehrlichman of City University of New York said that people tend to move their eyes about twice as often when people are considering a choice or sifting through long-term memory compared to when they are engaged in tasks that do not require them to think about the past.
Interestingly researchers noted these quick eye movements happen when people are n face-to-face situations, when they are in the dark, and when they have their eyes closed.
However, when scientists suppressed participants' involuntary eye movements, it made no impact on their memory creation, suggesting that, similar to the appendix, these saccadic eye movements serve no purpose and may be a throwback to an evolutionary trait that we no longer need.
Another study, published June 2012 in the journal Psychological Science found that a person's visual working memory can affect the precision of their memory.
Participants were asked to memorize the color and angle of either four or eight bars, which were colored red or green and were rotated either 15 or 45 degrees clockwise or counter clockwise.
Lead author Maro Machizawa of University College London found that when volunteers just had to remember four bars, they could retain more detail then remembering eight.
Machizawa concluded that these findings show that people can enhance the precision of the visual working memory only with a small number of items.