Hack62.The Broken Escalator Phenomenon: When Autopilot Takes Over


Hack 62. The Broken Escalator Phenomenon: When Autopilot Takes Over

Your conscious experience of the world and control over your body both feel instantaneousbut they're not.

Lengthy delays in sensory feedback and in the commands that are sent to your muscles mean that what you see now happened a few moments ago and what you're doing now you planned back then. To get around the problem caused by these delays in neural transmission, your brain is active and constructive in its interactions with the outside world, endlessly anticipating what's going to happen next and planning movements to respond appropriately.

Most of the time this works well, but sometimes your brain can anticipate inappropriately, and the mismatch between what your brain thought was going to happen and what it actually encounters can lead to some strange sensations.

6.2.1. In Action

One such sensation can be felt when you walk onto a broken escalator. You know it's broken but your brain's autopilot takes over regardless, inappropriately adjusting your posture and gait as if the escalator were moving. This has been dubbed the broken escalator phenomenon.1 Normally, the sensory consequences of these postural adjustments are canceled out by the escalator's motion, but when it's broken, they lead to some self-induced sensations that your brain simply wasn't expecting. Your brain normally cancels out the sensory consequences of its own actions [Hack #65], so it feels really weird when that doesn't happen.

To try it out yourself, the best place to look is somewhere like the London Underground (where you're sure to find plenty of broken escalators) or your favorite run-down mall. You need an escalator that is broken and not moving but that you're still allowed to walk up. You could also use the moving walkways they have at airports; again, you need one that's stationary but that you're still permitted to walk onto. Now, try not to think about it too much and just go ahead and walk on up the escalator. You should find that you experience an odd sensation as you take your first step or two onto the escalator. People often report feeling as though they've been "sucked" onto the escalator. You might even lose your balance for a moment. If you keep trying it, the effect usually diminishes quite quickly.

6.2.2. How It Works

Unless we've lived our lives out in the wilderness, most of us will have encountered moving escalators or walkways at least a few times. And when we've done so, our brain has learned to adapt to the loss of balance caused by the escalator's motion. It's done this with little conscious effort on our part, automatically saving us from falling over. So when we step onto an escalator or moving walkway now, we barely notice the transition, and continue fluidly on our way. The thing is, when the escalator is broken, our brain adjusts our balance and posture anyway, and it seems we can't stop it from doing so.

Until recently, evidence for this phenomenon was based only on urban anecdotes. But now the phenomenon has actually been investigated in the laboratory using a computer-controlled moving walkway.1,2 Special devices attached to the bodies and legs of 14 volunteers recorded their posture and muscle activity. Each volunteer then walked 20 times from a fixed platform onto the moving walkway. After that, the walkway was switched off, the volunteers were told it would no longer move, and they then walked from the platform onto the stationary walkway 10 times.

The first time the subjects stepped onto the moving walkway, they lost their balance and grasped the handrail. But over the next few attempts, they learned to anticipate the unbalancing effect of the walkway by speeding up their stride and leaning their body forward.

Then crucially, when the volunteers first walked onto the walkway when it was switched off, they continued to walk at the increased speed and also continued to sway the trunk of their body forward. They performed these inappropriate adjustments even though they could see the walkway was no longer moving and even though they had been told it would no longer move. However, this happened only once. Their brain had apparently realized the mistake and the next time they walked onto the stationary walkway they didn't perform these inappropriate adjustments. Consistent with anecdotal evidence for the broken escalator phenomenon, most of the volunteers expressed spontaneous surprise at the sensations they experienced when they first stepped onto the stationary walkway.

6.2.3. In Real Life

There are obviously differences between the lab experiment and the real-life phenomenon. Our brains have learned to cope with escalators over years of experience, whereas the experimental volunteers adapted to the lab walkway in just a few minutes. But what the real-life phenomenon and lab experiment both represent is an example of dissociation between our conscious knowledge and our brain's control of our actions. The volunteers knew the walkway was motionless, but because it had been moving previously, the brain put anticipatory adjustments in place anyway to prevent loss of balance. Usually these kinds of dissociations work the other way around. Often our conscious perception can be tricked by sensory illusions, but the action systems of our brain are not fooled and act appropriately. For example, visual illusions of size can lead us to perceptually misjudge the size of an object, yet our fingertip grasp will be appropriate to the object's true size. The motor system gets it right when our conscious perception is fooled by the illusion size (see [Hack #66] to see this in action).

These observations undermine our sense of a unified self: it seems our consciousness and the movement control parts of our brain can have two different takes on the world at the same time. This happens because, in our fast-paced world of infinite information and possibility, our brain must prioritize both what sensory information reaches consciousness and what aspects of movement our consciousness controls. Imagine how sluggish you would be if you had to think in detail about every movement you made. Indeed, most of the time autopilot improves performancethink of how fluent you've become at the boring drive home from work or the benefits of touch-typing. It's just that, in the case of the broken escalator, your brain should really have handed the reins back to "you."

6.2.4. End Notes

  1. Reynolds, R. F., & Bronstein, A. M. (2003). The broken escalator phenomenon. aftereffect of walking onto a moving platform. Experimental Brain Research, 151, 301-308.

  2. Reynolds, R. F., & Bronstein, A. M. (2004). The moving platform aftereffect: Limited generalization of a locomotor adaptation. Journal of Neurophysiology, 91, 92-100.

Christian Jarrett



    Mind Hacks. Tips and Tools for Using Your Brain
    Mind Hacks. Tips and Tools for Using Your Brain
    ISBN: 596007795
    EAN: N/A
    Year: 2004
    Pages: 159

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