Colors can tell us a lot about how we recognize shapes

[This entry was originally posted in April 2007]

ResearchBlogging.orgThe Beck effect is difficult to replicate online, because it involves testing reaction times. However, I think I've figured out a way to approximate the effect. This movie (Quicktime required) will show you how it works. Just follow the directions on the opening screen:

Now, which letter did you see first? Let's make this a poll:

If we manage to replicate the effect, there should be a bias in the results, which I'll explain below so everyone has a chance to try it out before learning the "answer."

In the 1960s, Jacob Beck found that when searching arrays of letters like this, viewers were faster to find the Ts tilted on their side than the standard Ls. Yet when asked simply to identify a sideways T or upright L by itself, viewers are equally fast for each letter. If we've successfully replicated it, more people should answer "T" than "L."

Interestingly, David Navon and Ruth Kimchi have found that the effect persists even when just two objects are being compared: We identify a sideways T next to an upright T faster than an L next to an upright T.

So what about identifying the T or L in when accompanied by upright Ts is different from identifying them alone? A couple of explanations have been proposed.

One explanation posits that when we're looking at a field of Ts, we're more attentive to similar shapes, so we notice the tilted Ts more rapidly. Another explanation argues that sideways Ts are actually less similar to upright Ts: since the Ls "blend in" we take longer to locate them.

Navon and Kimchi noted that both of these explanations rely on the specific shape of the letters. What if they could replicate the Beck effect without relying on shapes at all? In a 2004 study, they did just that. Instead of letters, they used colors. Viewers were shown four patches of color; three were always dark green, while the fourth could be either light green, dark green, or brown. They were told to press a corresponding button indicating which color the fourth patch was, and reaction times were measured. As a control they were also tested on single patches of each color. Here are the results:


When the colors were displayed by themselves, there was no significant difference in reaction time, but when they were shown among three dark green patches, the light green patches were identified significantly faster. Thus, Navon and Kimchi argue, they have demonstrated that the Beck effect applies not only to shapes, but also to colors. This makes both explanations of how the effect works problematic.

The researchers argue that the real source of the effect might be in the difference between judging between multiple possibilities and a single possibility. An analogy might be pregnancy: "Are you pregnant or not?" is an easier question to answer than "are you pregnant with a single fetus or twins?"

D. Navon, R. Kimchi (2004). The Beck effect is back, now in color: A demonstration Psychonomic Bulletin and Review, 11 (1), 98-103

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Interesting... but it would seem that your simulation is probably biased toward the sideways T, as the last line in the instructions (where the participant's eyes rest after reading the instructions) is exactly where the shape appears, whereas the L requires the participant to scan away from their last point of viewing.

I'd be interested to hear from some of the individuals who saw the L first whether they intentionally diverted their view from the instructions (flicked their view away, as it were) between instructions and field-of-characters.

By Martin Kuplens-Ewart (not verified) on 30 Dec 2008 #permalink

I saw the L first, but it was because I "read" it side to side, maybe five lines at a time looking for something odd rather than staring at the whole thing at once.

I agree with Martin and with the study. My eyes were in the same place as the sideways T when the video ran, but if I look at the end of the video again, it is much easier for me to spot the sideways T than the L.

There is overlap between this study and the psychology of visual aids when public speaking.

Slide design theory tells us that the eyes of the audience will be drawn first to the most salient feature on the slide. This might be the largest text (often the title), or the text highlighted in color (assuming the rest of the text is black), or the brightest or most unusual object on a visual slide.

Given this, it seems to me that the explanation for the bias toward the sideways "T" is that it differs the most from its background (the "sea" of upright T's). Note here that the longest segment of a upright T and an L is vertical, while the longest segment of a sideways T is horizontal.

By similar reasoning, I originally thought that the brown patches would be identified more quickly than the light green patches. (Reason: "brown" is more different than "dark green" than "light green" is.) The results confused me for a moment.

But, then I looked at the original article for the color values: The possible colors were light green, dark green, and brown (labeled a, b, and c, respectively). RGB values (weights of red, green, and blue in the additive mixture) were (0, 255, 153), (0, 102, 52), and (52, 50, 0) for a, b, and c, respectively.

When one converts the RGB values of those three colors to HSL (Hue, Saturation, and Lightness), the explanation is clear. Light green (Hue=156) and dark green (Hue=151) are closer in hue than brown (Hue=58). However, brown (Lightness=20) and dark green (Lightness=40) are closer in lightness than light green (Lightness=100).

So, in terms of colors, this research suggests that the eye is able to detect large variations in lightness the quickest.

Incidentally, I saw the tilted T first.

Many factors invalidate the T/L test here.

The depth of the page scroll affects where the eyes go at the start.

Telling the viewer to look for a sideways 'T' after telling about the 'L'.

Better to say nothing of the different letters.

Instead, say "In a field of T's, two letters shall exist which shall appear different. Find them."

Also, tell the viewer to scroll his page down far enough so that the embedded video player sits centered on his screen.

By Ketch Rudder (not verified) on 30 Dec 2008 #permalink

I agree with the other two commentators. If the position of the L and T had been swapped, I would have seen the L first.

hummm Well, I thought I saw the T first because it was in my view. But now I think I saw the L first, but was drawn to the T as it stood out more. And then I looked back to the L.
I guess I need one of those little cameras pointed at my eyes to see the 'eye dart'
That's my story and I'm sticking to it.

Here are my thoughts from a photographer's point of view. Think about the white space between all the Ts. The sideways T seems to be in the center of its white space. The L seems to frame the left and bottom of its white space. To my eyes, the sideways T contrasts more with its surrounding white space since it is centered in that white space, and is thus more noticeable to me.

When I cross my eyes and look at the image, the sideways T even seems to be in bold font and the L seems to be in regular font.

Lastly, if you divide the image into thirds vertically and horizontally, the sideways T is nearer than the L to one of the intersections, which is where photographers are taught to generally place the subjects of the photographs within the frame (rule of thirds).

Are the results the same if the positions of the characters in question are switched within the image?

By jeremy allen (not verified) on 30 Dec 2008 #permalink

I agree with Martin and others - the sideways T was already in the line of sight, and the L was outside of my line of sight. You may be interested in reviewing the significant research regarding tracking eye motion on web pages and advertisements. The position of the letter definitely had an impact on me. Also, you may want to consider modifying the simulation (if you can), to randomly move letters around on the page. Then the "variable" of your experiment is truly the change in letter (rather than the letter's position on the page).

i guess this would make sense mathematically if we treat our brains' cognitive skills to parallel correlation techniques. In my opinion, the tilted T would give a higher correlation difference than the letter L.

By Siddharth Vaghela (not verified) on 13 Jan 2009 #permalink

I saw the tilted T first. In addition to the reasons stated above, I also think the fact that the T is thicker than the L might have some effect. The T is actually 2 pixels in width, while the L is only 1 pixel. In effect, the T is bolded compared to the L. Just looking at the array of letters, the bold horizontal bar of the T stands out like a sore thumb (to me). Granted, the other T's have a horizontal bar as well, but they're interrupted by the vertical bar at the center. My 2 cents :)