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We're convinced that free will exists, but new research suggests it might be nothing more than a trick the brain plays on itself.


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What neuroscience says about free will:

It happens hundreds of times a day: We press snooze on the alarm clock, we pick a shirt out of the closet, we reach for a beer in the fridge. In each case, we conceive of ourselves as free agents, consciously guiding our bodies in purposeful ways. But what does science have to say about the true source of this experience?

In a classic paper published almost 20 years ago, the psychologists Dan Wegner and Thalia Wheatley made a revolutionary proposal: The experience of intentionally willing an action, they suggested, is often nothing more than a post hoc causal inference that our thoughts caused some behavior. The feeling itself, however, plays no causal role in producing that behavior. This could sometimes lead us to think we made a choice when we actually didn’t or think we made a different choice than we actually did.

But there’s a mystery here. Suppose, as Wegner and Wheatley propose, that we observe ourselves (unconsciously) perform some action, like picking out a box of cereal in the grocery store, and then only afterwards come to infer that we did this intentionally. If this is the true sequence of events, how could we be deceived into believing that we had intentionally made our choice before the consequences of this action were observed? This explanation for how we think of our agency would seem to require supernatural backwards causation, with our experience of conscious will being both a product and an apparent cause of behavior.

In a study just published in Psychological SciencePaul Bloom and I explore a radical—but non-magical—solution to this puzzle. Perhaps in the very moments that we experience a choice, our minds are rewriting history, fooling us into thinking that this choice—that was actually completed after its consequences were subconsciously perceived—was a choice that we had made all along.

Though the precise way in which the mind could do this is still not fully understood, similar phenomena have been documented elsewhere. For example, we see the apparent motion of a dot before seeing that dot reach its destination, and we feel phantom touches moving up our armbefore feeling an actual touch further up our arm. “Postdictive” illusions of this sort are typically explained by noting that there’s a delay in the time it takes information out in the world to reach conscious awareness: Because it lags slightly behind reality, consciousness can “anticipate” future events that haven’t yet entered awareness, but have been encoded subconsciously, allowing for an illusion in which the experienced future alters the experienced past.

Maybe the brain has good reason for deceiving us.

In one of our studies, participants were repeatedly presented with five white circles in random locations on a computer monitor and were asked to quickly choose one of the circles in their head before one lit up red. If a circle turned red so fast that they didn’t feel like they were able to complete their choice, participants could indicate that they ran out of time. Otherwise, they indicated whether they had chosen the red circle (before it turned red) or had chosen a different circle. We explored how likely people were to report a successful prediction among these instances in which they believed that they had time to make a choice.

Unbeknownst to participants, the circle that lit up red on each trial of the experiment was selected completely randomly by our computer script. Hence, if participants were truly completing their choices when they claimed to be completing them—before one of the circles turned red—they should have chosen the red circle on approximately 1 in 5 trials. Yet participants’ reported performance deviated unrealistically far from this 20% probability, exceeding 30% when a circle turned red especially quickly. This pattern of responding suggests that participants’ minds had sometimes swapped the order of events in conscious awareness, creating an illusion that a choice had preceded the color change when, in fact, it was biased by it.

Importantly, participants’ reported choice of the red circle dropped down near 20% when the delay for a circle to turn red was long enough that the subconscious mind could no longer play this trick in consciousness and get wind of the color change before a conscious choice was completed. This result ensured that participants weren’t simply trying to deceive us (or themselves) about their prediction abilities or just liked reporting that they were correct.

In fact, the people who showed our time-dependent illusion were often completely unaware of their above-chance performance when asked about it in debriefing after the experiment was over. Moreover, in a related experiment, we found that the bias to choose correctly was not driven by confusion or uncertainty about what was chosen: Even when participants were highly confident in their choice, they showed a tendency to “choose” correctly at an impossibly high rate.

Taken together, these findings suggest that we may be systematically misled about how we make choices, even when we have strong intuitions to the contrary. Why, though, would our minds fool us in such a seemingly silly way in the first place? Wouldn’t this illusion wreak havoc on our mental lives and behavior?  

Maybe not. Perhaps the illusion can simply be explained by appeal to limits in the brain’s perceptual processing, which only messes up at the very short time scales measured in our (or similar) experiments and which are unlikely to affect us in the real world.

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