Hack56.Don t Go There

Hack 56. Don't Go There

You're drawn to reach in the same direction as something you're reacting to, even if the direction is completely unimportant.

So much of what we do in everyday life is responding to something that we've seen or heardchoosing and clicking a button on a dialog box on a computer or leaping to turn the heat off when a pan boils over. Unfortunately, we're not very good at reacting only to the relevant information. The form in which we receive it leaks over into our response.

For instance, if you're reacting to something that appears on your left, it's faster to respond with your left hand, and it takes a little longer to respond with your right. And this is true even when location isn't important at all. In general, the distracting effect of location responses is called the Simon Effect,¹ named after J. Richard Simon, who first published on it in 1968 and is now Professor Emeritus at the University of Iowa.2

The Simon Effect isn't the only example of the notionally irrelevant elements of a stimulus leaking into our response. Similar is the Stroop Effect [Hack #55], in which naming an ink color nets a slower response if the ink spells out the name of a different color. And, although it's brought about by a different mechanism, brighter lights triggering better reaction times [Hack #11] is similar in that irrelevant stimulus information modifies your response (this one is because a stronger signal evokes a faster neural response).

5.5.1. In Action

A typical Simon task goes something like this: you fix your gaze at the center of a computer screen and at intervals a light flashes up, randomly on the left or the rightwhich side is unimportant. If it is a red light, your task is to hit a button on your left. If it is a green light, you are to hit a button on your right. How long it takes you is affected by which side the light appears on, even though you are supposed to be basing which button you press entirely on the color of the light. The light on the left causes quicker reactions to the red button and slower reactions to the green button (good if the light is red, bad if the light is green). Lights appearing on the right naturally have the opposite effect. Even though you're supposed to disregard the location entirely, it still interferes with your response. The reaction times being measured are usually a half-second or less for this sort of experiment, and the location confusion results in an extension of roughly 5%.

It's difficult to tell what these reaction times mean without trying the experiment, but it is possible to feel, subjectively, the Simon Effect without equipment to measure reaction time.

You need stimuli that can appear on the left or the right with equal measure. I popped outside for 10 minutes and sat at the edge of the road, looking across it, so traffic could come from either my left or my right. (Figure 5-2 shows the view from where I was sitting.) My task was to identify red and blue cars, attempting to ignore their direction of approach.

Figure 5-2. The view from where I sat watching for red and blue cars

In choosing this task, I made use of the fact that color discrimination is poor in peripheral vision [Hack #14] . By fixing my gaze at a position directly opposite me, over the road, and refusing to move my eyes or my head, I would be able to tell the color of each car only as it passed directly in front of me. (If I had chosen to discriminate black cars and white cars, there's no color information required, so I would have been able to tell using my peripheral vision.) I wanted to do this so I wouldn't have much time to do my color task, but would be able to filter out moving objects that weren't cars (like people with strollers).

As a response, I tapped my right knee every time a red car passed and my left for blue ones, trying to respond as quickly as possible.

After 10 minutes of slow but steady traffic, I could discern a slight bias in my responses. My right hand would sometimes twitch a little if cars approached from that direction, and vice versa.

Now, I wouldn't be happy claiming a feeling of a twitchy hand as any kind of confirmation of the Simon Effect. The concept of location in my experiment is a little blurred: cars that appear from the right are also in motion to the leftwhich stimulus location should be interfering with my knee-tapping response?

But even though I can't fully claim the entire effect, that a car on the right causes a twitching right hand, I can still claim the basic interference effect: although I'd been doing the experiment for 10 minutes, my responses were still getting mucked up somehow.

To test whether my lack of agility at responding was caused by the location of the cars conflicting with the location of my knees, I changed my output, speaking "red" or "blue" as a response instead. In theory, this should remove the impact of the Simon Effect (because I was taking away the left-or-right location component of my response), and I might feel a difference. If I felt a difference, that would be the Simon Effect, and then its lack, in action.

And indeed, I did feel a difference. Using a spoken output, responding to the color of the cars was absolutely trivial, a very different experience from the knee tapping and instantly more fluid.

5.5.2. How It Works

For my traffic watching exercise, the unimportant factor of the location of the colored cars was interfering with my tapping my left or right knee. Factoring out the location variable by speaking instead of knee tappingeffectively routing around the Simon Effectmade the whole task much easier.

Much like the Stroop Effect [Hack #55] (in which you involuntarily read a word rather than sticking to the task of identifying the color of the ink in which it is printed), the Simon Effect is a collision of different pieces of information. The difference between the two is that the conflict in the Stroop Effect is between two component parts of a stimulus (the color of the word and the word itself), while, in the Simon Effect, the conflict is between the compatibility of stimulus and response. You're told to ignore the location of the stimulus, but just can't help knowing location is important because you're using it in making your response.

The key point here is that location information is almost always important, and so we're hardwired to use it when available. In real life, and especially before the advent of automation, you generally reach to the location of something you perceive in order to interact with it. If you perceive a light switch on your left, you reach to the left to switch off the lights, not to the rightthat's the way the world works. Think of the Simon Effect not as location information leaking into our responses, but the lack of a mechanism to specifically ignore location information. Such a mechanism has never really been needed.

5.5.3. In Real Life

Knowing that location information is carried along between stimulus and response is handy for any kind of interface design. My range has four burners, arranged in a square. But the controls for those burners are in a line. It's because of the Simon Effect that I have to consult the diagram next to the controls each and every time I use them, not yet having managed to memorize the pattern (which, after all, never changes, so it should be easy). When I have to respond to the pot boiling over at the top right, I have the top-right location coded in my brain. If the controls took advantage of that instead of conflicting, they'd be easier to use.

Dialog boxes on my computer (I run Mac OS X) are better aligned with keyboard shortcuts than my stove's controls with the burners. There are usually two controls: OK and Cancel. I can press Return as a shortcut for OK and Escape as a shortcut for Cancel. Fortunately, the right-left arrangement of the keys on my keyboard matches the right-left arrangement of the buttons in the dialog (Escape and Cancel on the left, Right and OK on the right). If they didn't match, there would be a small time cost every time I attempted to use the keyboard, and it'd be no quicker at all.

And a corollary: my response to the color of the cars in the traffic experiment was considerably easier when it was verbal rather than directional (tapping left or right). To make an interface more fluid, avoid situations in which the directions of stimulus and response clash. For technologies that are supposed to be transparent and intuitivelike my Mac (and my stove, come to that)small touches like this make all the difference.

5.5.4. End Notes

1. Simon, J. R. (1969). Reactions toward the source of stimulation. Journal of Experimental Psychology, 81, 174-176.

2. In fairness, we should mention that the Simon Effect was actually noted a hundred years before Simon published, by the pioneering Dutch experimental psychologist Franciscus Donders. Donders, Franciscus C. (1868). Over de snelheid van psychische processen. Onderzoekingen gedaan in het Physiologisch Laboratorium der Utrechtsche Hoogeschool, 1868-1869, Tweede reeks II: 92-120. Reprinted as Donders, Franciscus C. (1969). On the speed of mental processes. Acta Psychologica, 30, 412-431.

5.5.5. See Also

• You can read about the early history of measuring reaction times at "Mental Chronometry and Verbal ActionSome Historical Threads" (http://www.mpi.nl/world/persons/private/ardi/Rts.htm).