- 16 Oct, 2024
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Multitasking Myth: How Your Brain Juggles (And Sometimes Drops) Tasks
Imagine this: you’re driving along a busy highway, talking to your friend in the passenger seat. Suddenly, a car swerves into your lane. Your heart skips a beat, and you instinctively reach for the brakes. But have you ever wondered why, in moments like this, your response can sometimes feel delayed—like there’s a split-second pause between seeing the car and hitting the brakes? This is where the Psychological Refractory Period, or PRP, comes into play.
The PRP is a curious quirk of our brain’s multitasking abilities. It’s what happens when two different tasks are thrown at us at nearly the same time. The result? A slight but noticeable delay in handling the second task. In this driving scenario, the PRP explains why your reaction to the swerving car might be a little slower because your brain is already juggling another task: holding a conversation.
To understand why this delay happens, let’s take a peek inside our brain’s decision-making process. Every task our brain handles goes through three stages: perceiving what’s happening (Perceptual Stage), deciding how to react (Central Stage), and then actually doing something about it (Motor Stage). The real bottleneck occurs during the Central Stage, where we decide on an action. This is like the ultimate decision traffic jam—our brain can only make one choice at a time, even if we’re capable of doing many things at once. When we’re asked to pick between braking or swerving, this decision-making process holds up the line.
The PRP bottleneck becomes even clearer when scientists examine it through clever experiments. Imagine you’re asked to compare two numbers—a purely visual task. At the same time, you’re also asked to identify a sound, like a tone—an auditory task. You have to use your left hand for the visual task and your right hand for the tone. The researchers can change the timing between these tasks, called the “stimulus onset asynchrony” or SOA, to see how your brain handles them.
The results are fascinating. If the two tasks arrive at almost the same time, our brain can process the sensory inputs together—seeing the numbers and hearing the tone—without a problem. But when it comes to making decisions about those inputs, it’s like the brain suddenly hits a queue. The Central Stage can only process one decision at a time, so the second task has to wait until the first decision is made before getting its turn. It’s like being in line at a crowded coffee shop, where only one barista is taking orders while the other baristas make the drinks.
And it doesn’t stop there. The experiments showed how different aspects of each task affect the bottleneck. When participants had to tap once or twice in response, the delay added time to the first task, but it didn’t affect the second task at all—it turns out, this delay was happening after the bottleneck, in the motor stage. On the other hand, when participants had to deal with different ways of presenting numbers (a “notation” manipulation), it only affected them when there was enough of a gap between the tasks—which meant that the perception part of the task was working in parallel with the other task.
These results reveal something pretty cool about our brains. They show that while some parts of multitasking are like waiting in line at that crowded coffee shop, other parts are more like different baristas making drinks at the same time. Some stages are purely serial—one thing after another—while others happen in parallel, with multiple processes unfolding together.
In the end, every experiment confirmed the same story: our brains are both amazing and a bit limited in their ability to juggle. Some stages of processing are bound by bottlenecks, creating a delay when two decisions demand attention at once. Yet, at the same time, other aspects of tasks can unfold in beautiful synchrony. The Psychological Refractory Period isn’t just a mouthful of scientific jargon—it’s a window into how our minds cope with the demands of our busy, multitasking lives. It’s a reminder that even though we try to do it all, sometimes our brain just needs a moment to finish one thing before it can move on to the next.
Reference :
Sigman, Mariano; Dehaene, Stanislas (2011): Why does it take time to make a decision? The role of a global workspace in simple decision making. In Oshin Vartanian, David R. Mandel (Eds.): Neuroscience of decision making: Psychology Press (Neuroscience of decision making), pp. 11–44.