Hack38.Don t Look Back


Hack 38. Don't Look Back!

Your visual attention contains a basic function that puts the dampers on second glances.

There are layers and layers of functions and processing in the brain. Oneattentionis a collaborative exercise between voluntary application of attention and automatic mechanisms to snap attention to where it's needed [Hack #37] . Even the voluntary application of attention is a negotiation with what evolution has taught the brain is most sensible. In particular, the brain doesn't like to return attention to a place or object it has just left. This phenomenon is called inhibition of return.

3.6.1. In Action

Like negative priming [Hack #42], which is how contextual features are suppressed from attention, inhibition of return is such a low-level effect that it's hard to show without precision timing equipment. Again, just like those other effects, it turns up in all kinds of cases because attention is so widely employed.

Imagine you're taking part in an experiment in which an icon flashes up on a screen and you have to touch that position. It'll take you longer to move and touch the icon if some other icon had previously, and recently, been in that position.

Inhibition doesn't kick in immediately. Let's say you're playing Whack-A-Mole,1 in which moles emerge from holes and you have to hit them with a hammer. A hole could light up momentarily before the mole appears. This would be a prime candidate for the inhibition-of-return effect. If the brightening occurs very shortly before the mole appears, only a fifth of a second or so, it serves to draw your attention to that place and you'll actually respond to the mole faster.

If, on the other hand, the brightening occurs and then there's a longer pausemore than a fifth of a second and up to 3 or 4 secondsthat's enough time for your attention to be dragged to the brightness change then shift away again. Inhibition of return kicks in, and when the mole appears in that same spot, you have to overcome the inhibition. It'll take longer for you to react to the mole (although it's not likely you'll miss it. Reaction time increases only on the order of a twentieth of a second or soenough to make a difference in some circumstances, but hard to spot.) One caveat: if the brightening happens before the mole pops up every single time, you're going to learn that pattern and end up being better at whacking the mole every time instead.

3.6.2. How It Works

The big question is why this happens. One possibility is that it's because we prefer novelty and want to suppress distracting stimuli. An attention-grabbing event is good if it's useful, but if it's not the event we're looking for, then we're better off focusing our attention elsewhere in the future and ignoring that distracting location.

Raymond Klein, in his review paper "Inhibition of Return,"2 gives the example of efficient foraging for food. He suggests that potential locations that have been found bare should be remembered as places to be avoided, and this acts as a mechanism to orient toward novel locations. This could be used just standing in one place and looking ahead to find edible plants on the ground. For a task like visually searching straight ahead, it would be extremely useful to have a mechanism that allows you to briefly look harder (for a fifth of a second) and helps you to look for novel locations (for a few seconds after).

Current research indicates there may be two ways in which inhibition of return is produced. One is at a very low level, subcortically in the superior colliculus, which does rapid visual processing (but isn't responsible for our conscious visual processing [Hack #13], which takes longer) and helps orient the pupils and body. Indeed, damage to this part of the brain stops inhibition of return from taking place3, at least for stopping the eyes moving back to locations they've previously been.

Inhibition of return could also be triggered by higher-level operations in the allocation of attention. The fact that the inhibition remains in place even when the objects are moving around supports thisit can no longer rely on just eye position. Think of counting a crowd of people when they're all moving around: you're able to do this because you can deselect people who have already been counted. This is the inhibition of return in play.

3.6.3. In Real Life

In fact, that this mechanism crops up in more than one place in the brain points to it being a good, generic solution to tricky search problems, rather than a workaround for some problem specific to a particular function like feature processing. I can see the same strategy coming into play when I'm looking for something I've lost in my house. I'll search one location pretty thoroughly, then move on to the next, and the next, and the next. If someone suggests I return to my first location and look there again, I'm pretty reluctant. After all, I would have found it first time around, right?

If this is a common strategy in search, there are some pointers for interface design. Don't attract people's attention to a place briefly if you really want to grab their attention there shortly after. So if a news ticker on a web site, for example, appears with a flash but then has a 2-second pause before the news appears on it, people aren't going to notice the news coming up. The initial flash will have inhibited their attention returning there for the subsequent few seconds. If something is going to happen, make it happen immediately, not after a brief pause. When people are skimming over stuff, they don't want to have their attention squanderedinhibition of return makes second glances less likely.

3.6.4. End Notes

  1. Spy Whack-A-Mole, using Flash (http://www.spymuseum.org/games/mole.html), lets you play the game and simultaneously learn about the past 100 years of spying.

  2. Klein, R. M. (2000). Inhibition of return. Trends in Cognitive Science, 4(4), 138-147.

  3. Sapir, A., Soroker, N, Berger, A., & Henik, A. (1999). Inhibition of return in spatial attention: Direct evidence for collicular generation. Nature Neuroscience, 2(12), 1053-1054.



    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

    flylib.com © 2008-2017.
    If you may any questions please contact us: flylib@qtcs.net