Comments on: Every time you reach for something, there’s a squabbling match in your brain

By: Andrew Wilson

Andrew Wilson — Wed, 29 Sep 2010 14:41:06 +0000

I feel obliged to point out that a lot of the ‘decision making’ has already taken place by the time a given reach is executed. For instance, the affordances of the object have already ruled out many (technically possible) reaches and constrained the decision space. Biases such as recent movement history then further constrain the space (several researchers have gotten interested in this recently, we cite some in Kent et al). On a longer time scale ‘use dependant learning’ creates reaching-to-grasp perception/action systems that do what you typically do, meaning many (technically possible) reaches aren’t ever actually options. The brain is only part of the system that ‘decides’ and it’s not at all clear that ‘decision’ is the correct description of what is actually a complex, time extended dynamic process.

Brian Too, the net result is that the space of possibilities, while still large for any given reach-to-grasp action, is not infinite or even likely to contain really unusual options, unless there’s genuine malfunction in the system. Just because a patient with frontal lobe damage might generate and fail to inhibit tipping the table doesn’t mean normal function requires inhibiting such an option.

Kent, SW; Wilson, AD; Plumb, MS; Williams, JH; Mon-Williams, M Immediate movement history influences reach-to-grasp action selection in children and adults. J Mot Behav, 41, 10-15, 2009

By: Ed Yong

Ed Yong — Tue, 28 Sep 2010 19:40:36 +0000

Ha! The price of knowledge!

By: Aurora

Aurora — Tue, 28 Sep 2010 19:32:41 +0000

I’m about to reach for my cup of tea, and there’s now a 3rd set of voices in my head, whispering: “You’ve triggered the shouting-match again…”

By: Chris M.

Chris M. — Tue, 28 Sep 2010 03:23:41 +0000

The left-handed suggestion is interesting; you’d think people who were ambidextrous (or some approximation of it) would be better. Much harder to find as research subjects, but in this case the effort is probably worth it given the difficulty of proving the findings. Of course, if you do get the same sidedness result for the more easily-found left handers, it strongly supports lateral specialization in the brain. Does anyone know whether that’s been shown for motor tasks, outside handedness? I can’t recall myself.

By: Ed Yong

Ed Yong — Mon, 27 Sep 2010 23:43:32 +0000

Yep, this sort of competitive decision-making is known (although more recently that you might imagine). The “new” bit is the relevance of hand choice.

But I don’t like news stories that only focus on the latest new bit. It’s not how science works. New discoveries sit on the shoulders of giants. In this case, yes, there’s a news hook (hand choice) but it also gave me a chance to talk about this aspect of decision-making that’s not well known to a general audience.

By: Brian Too

Brian Too — Mon, 27 Sep 2010 23:23:55 +0000

I thought this was known already? Haven’t psychologists already established that any time action is considered, the brain produces an array of possibilities and then inhibits most of them? I thought it was known as dampening or something similar.

Even radical and anti-social possibilities are produced. For instance, to extend the example given in the article, you might consider tipping the entire table over in order to get the cup. Then you discard that possibility, thinking “no, that might break the cup”, or any of a thousand other reasons not to do that. It all happens very quickly too and can operate under the threshold of perception.

By: jtradke

jtradke — Mon, 27 Sep 2010 20:06:36 +0000

Whoa whoa whoa. You can shut off somebody’s brain with a magnetic field? Where do I get that in handheld form? Life could be far more slapstick…

By: Rhacodactylus

Rhacodactylus — Mon, 27 Sep 2010 19:34:58 +0000

Now Ed, should I actually hear the voices yelling at each other, because my Dr feels we should try to control that with medication?