Limitations of human sensorimotor systems? Part 3


If you have not read part 1 & 2, they are worth reading, but here is the summary.

  1. Human brain demonstrates its amazing ability to predict and learn while trying to solve the problems related to the limitations of our default motor control system.

  2. The first limitation of our motor control system has to do with the fact that each sensory information is only specific to sensory receptors that send the information. To get the whole picture of the context we are in, the brain has to integrate information coming from the various sensory receptors.

  3. Integration of the sensory information inevitably amplifies inherent error within each sensory signal.

Now I am going to talk about the third limitation of our sensorimotor control system which is much more intuitive to understand compared to the 1st and 2nd limitations.

  • Limitation #3: All of the sensory information is inherently outdated

Let's think about intercepting a tennis ball. We use our vision to see how far the tennis ball is from our body and how fast the ball is coming towards us. However, it takes at least 100 msec for the brain to receive and process such information. So by the time our brain interprets where the ball is, the ball is actually closer to us than we think. In case of professional tennis competition, the tennis ball can fly at about 120km / hr. That means the difference between perceived location and actual location of the ball can be about 3cm. This error in perception is significant enough to cause a serious miss shot.

The problems related to delay in signal processing is not specific to visual information. Any sensory signal has to travel certain distance to get to the brain. Therefore, any sensory signals are inherently outdated.

All of our sensory information is outdated! That is crazy, but it is so true. This means that we don't truly perceive the present. A cognitive neuroscientist, Anil Seth, once said that we can't just passively perceive the world. Instead, our brain generates the perception of the world using a controlled hallucination. I will talk about this more in detail when I talk about how our brain overcomes the limitations of the sensorimotor system.

In the next posting, I will talk about the 4th limitation of the sensorimotor system, which I think one of the most relevant to goal-directed action. It is rather complex to understand. So stay tuned and get ready to brace yourself!

Reference

Wolpert, D. M., Ghahramani, Z., & Flanagan, J. R. (2001). Perspectives and problems in motor learning. Trends in cognitive sciences, 5(11), 487-494.