Do Your Eyes Give You Away? Scientific Research on Eyes & Lying

Can your eyes give away how much you’re thinking — even when you’re not consciously aware of your effort? According to new research, the answer is yes.

Previous research has shown that people spend more physical effort in a demanding physical task when they could gain a high-value monetary reward, than when they could gain a low-value reward. But the intriguing finding from this research was that this behavior occurred even when the monetary reward was presented subliminally, below the threshold of our conscious awareness. In other words, a person would work harder for more money, even if they weren’t consciously aware that more money was the reward. Other research into subliminal processing suggests people can perceive emotional messages subliminally too.

Dutch researcher Erik Bijleveld and colleagues recruited 15 participants to take part in an experiment measuring cognitive effort on a task for various amounts of money. They measured the brain effort required to complete the task through eye pupil dilation. Why would you care about pupil dilation, an automatic nervous system response? Well, it appears that you can tell a lot by the size of your pupils, because it expands with sympathetic activity, making it an unobtrusive measure of how much mental effort you’ve invested in a particular task.

The study was task was simple number recall of either three or five-digit numbers for various amounts of money. Sometimes the amount of money earned was show subliminally and sometimes it was shown explicitly. Participants completed 48 trials of the task, earning money as they went. Pupil dilation was measured by a scientific instrument designed for such measurements.

In keeping with the previous researcher, the current study’s researchers found that more valuable rewards led to recruitment of more mental resources, even when the participants were not consciously aware that the task would result in a larger monetary reward.

But they also found that people didn’t just call on more mental resources arbitrarily for all high-reward tasks — they only did so when the task was difficult and the participant required more mental effort to complete the task. A person’s pupils dilated more when they were thinking harder on harder tasks, even when they weren’t consciously aware of the higher reward associated with that task.

The researchers summarized their findings succinctly:

“More generally, whereas analyses of costs (required effort) and benefits (value of rewards) are usually thought to require consciousness, our findings suggest that such strategic processes can occur outside of awareness — and these processes show in the eyes.”

While the researchers studied pupil dilation with scientific instruments, their findings into these microexpressions may be able to be generalized to other kinds of interactions with others. For instance, imagine an interrogation by a police detective investigating a crime. The valuable reward in such an example is not monetary, but rather freedom versus being jailed. A suspect who’s pupils are dilating while describing their alibi may be calling upon more mental resources when they making it up (since a lie requires more mental resources for most people than simply telling the truth).

This is a tiny experiment, however, so some caution must be used in over-reaching in interpreting these results. Further study will be needed to confirm these results on a larger and more diverse population. But the data from this small study suggest that it may be possible that your eyes may indeed tell others how much you’re thinking, even when you’re not consciously aware of your own mental efforts.

Research on Eyes Giving Away A Lie

There is some scientific evidence that suggests certain eye movements can indicate when a person is lying. For example, studies have found that when someone is lying, they tend to blink less frequently and make less eye contact. However, these indicators are not definitive, and many factors such as nervousness, stress, and anxiety can also cause similar eye movements. Additionally, people can learn to control their eye movements and avoid giving away their lies. Overall, the evidence for using eye movements as a reliable indicator of lying is mixed, and more research is needed to establish a solid connection.

Studies have shown that during a lie, people may experience stress, which can lead to physiological changes, such as changes in eye movements, that could be indicative of lying. For instance, one study found that people blink less when lying compared to when they are telling the truth, and that this reduction in blinking may be related to increased cognitive load during lying.

Another study found that people tend to avoid eye contact and make fewer eye movements when lying, which is thought to be related to a fear of being caught. Additionally, some studies suggest that people who are lying are more likely to look up and to the right, while those who are telling the truth are more likely to look directly at the person they are talking to.

However, it’s important to note that these findings are not definitive, and that many other factors, such as nervousness, stress, and anxiety, can also influence eye movements. Furthermore, people can learn to control their eye movements, making it difficult to accurately detect lies based on eye movements alone.

In conclusion, while there is some evidence to suggest that eye movements can indicate lying, these indicators should not be relied upon as the sole means of determining whether someone is lying, as many other factors can affect eye movements, and the evidence is far from conclusive.

 

Reference:

Bijleveld, E., Custers, R. & Aarts, H. (2009). The Unconscious Eye Opener: Pupil Dilation Reveals Strategic Recruitment of Resources Upon Presentation of Subliminal Reward Cues. Psychological Science. DOI: 10.1111/j.1467-9280.2009.02443.x.