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Too Hard for Science? Regaining the Element of Surprise

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How do you repeat experiments that require volunteers to not know what’s next?

In "Too Hard for Science?" I interview scientists about ideas they would love to explore that they don’t think could be investigated. For instance, they might involve machines beyond the realm of possibility, such as particle accelerators as big as the sun, or they might be completely unethical, such as lethal experiments involving people. This feature aims to look at the impossible dreams, the seemingly intractable problems in science. However, the question mark at the end of "Too Hard for Science?" suggests that nothing might be impossible.

The scientist: Daniel Simons, professor of psychology at the University of Illinois and co-author of   "The Invisible Gorilla: How Our Intuitions Deceive Us," which came out in paperback on June 7.

The idea: A now-famous experiment that Simons conducted with Christopher Chabris more than a decade ago involved a video showing two groups of people — some dressed in white, some in black — passing basketballs back and forth. They asked volunteers to count the passes among those dressed in white while ignoring the passes of those in black. (If you have not watched the video, stop reading and test your own skill at this task by visiting here before scrolling down.)











Astoundingly, half of those who watched the video failed to notice when a person in a gorilla suit walked into the game, faced the camera, pounded on its chest and then strolled out of view. The study revealed that people can focus so hard on something that they become blind to the unexpected, even when staring right at it, an effect called "inattentional blindness."

"The one question I get asked more than any other — almost every time I speak or write about this — is whether some people are better at noticing unexpected things than others," Simons says.

Determining whether some people are better at noticing the unexpected than others could be invaluable. "There would be huge implications for people who work in security," he notes. "Who is more likely to spot rare but really dangerous events?"

To find out, an experiment has to essentially show volunteers one scene repeatedly to see whether some are better at noticing unexpected details in that scene than others. "You really would want to test them with the same scene again to see whether there is a stable individual difference," Simons explains —   whether the same people detect the same event each time.

The problem: "As soon as you ask people whether they noticed an unexpected detail, it will never again be unexpected," Simons says. "And if you then test them with the same scene a second time, they’ll be looking for the details they missed the first time."

Ideally one would somehow wipe the memories of volunteers right after each test. Although there are ways to induce amnesia, such as amnestic drugs or electrical shocks, "there’s no way to target a specific memory, to wipe out a narrow time window," Simons says. You would want to wipe out just their memory for having done the task and nothing more. Of course, "you’d also want volunteers in a normal state of mind, and not drugged, for instance."

There are people with anterograde amnesia who have lost or have an impaired ability to form new memories who might conceivably be able to take these tests repeatedly. However, that kind of amnesia can have all kinds of complications which might influence their performance, making it hard to generalize their results to everyone else, Simons adds.

The solution? Researchers can instead test thousands of people with invisible gorillas and analyze what factors those who happen to notice have in common, if any. "That’s not as good as testing the same people repeatedly, but it might be all we can do," Simons says.

(Incidentally, while many find the results of the "invisible gorilla" test hard to believe, subsequent research delving further into this effect revealed that people who know about it and are looking for the invisible gorilla are no better at noticing other unexpected events — and may even be worse at noticing them — than others who aren’t expecting the unexpected.)

Image of Daniel Simons from the University of Illinois’ Web page.


If you have a scientist you would like to recommend I question, or you are a scientist with an idea you think might be too hard for science, e-mail me at

Follow Too Hard for Science? on Twitter by keeping track of the #2hard4sci hashtag.

About the Author: Charles Q. Choi is a frequent contributor to Scientific American. His work has also appeared in The New York Times, Science, Nature, Wired, and LiveScience, among others. In his spare time he has traveled to all seven continents. Follow him on Twitter @cqchoi.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. denysYeo 8:15 pm 06/10/2011

    A really interesting area of study!

    Since I read the "Invisible Gorilla" a little while back I have noticed a number of instances where something new has featured in my daily landscape but even though I must have seen, or even heard it for some time, it did not register until it had been pointed out to me. (each time I say to myself – it’s that damn gorilla again!) On the other hand, there are also occasions where I notice changes that others (who have also been exposed to "my" landscape) have not been aware of until I point out the new feature. This suggests to me that it is not only important (albeit as you note very difficult) to look for between people differences in this effect, but also within people differences. For example, at a basketball game, would some security guards be better at spotting the appearance of the gorilla, and others better at spotting the appearance of a player in a red shirt?

    Also, as a starting point, it’s possible that within people variation would be easier to investigate than between people variations?

    Link to this

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