Cheetah or armadillo? Check your reaction speed

You may not like the results, but here’s a quick test of your eye-hand response speed. It’s a little game on the BBC’s site, part of their section on the human body. This part is about sleep, because being tired increases reaction time. Your job is to use a dart gun when sheep at one side of the screen


make a run for the other side. The dart gun will stop them in their tracks.


Don’t get an itchy trigger finger, though, because a false move costs you 3 seconds of time in which sheep can run across with impunity. At the end—5 sheep—you’ll get a rating, and a list of your exact times to the thousandth of a second.

These are the fastest sheep I ever saw, and my rating never rose above Ambling Armadillo. Use the link above rather than the one on the BBC’s main Sleep page, because that one goes to a small screen version which gives you even less time to nail those pesky sheep.

Too bad the BBC isn’t using this as an opportunity to collect data; if we all gave our age and sex, they’d have a big sample for correlating those factors with reaction time. How long the time is, depends on mental processing speed; it’s in your brain, not your muscles (although while darting sheep I found that my index finger clicked my laptop trackpad button faster than my thumb, which is usually what I click with in normal computing). Some of the brain-game sellers say their games improve reaction time, and that seems quite believable; athletes practice to increase their reaction speed, and pianists get faster with practice. I’d be interested in knowing how much of the improvement from computer brain games is transferable to non-game situations, though. And naturally the fastest reaction times occur when there is only one action to be chosen: you’re going to be faster using the dart gun against the sheep, than responding to a complex driving emergency where you must decide whether to swerve or brake, how much, and how fast.

Reaction times become longer with age (after the late 20’s, according to this literature review on reaction times), fatigue, distraction, and a variety of other factors. And, when times are measured in thousandths of a second, a single individual will exhibit quite a bit of variation even in a single testing session. The literature review cited was done in 2008 and seems to be a good summary of what’s known.

Looking for more about reaction times, I found another online test which doesn’t have any cute sheep but does track and display the data from all users. It’s not broken down by age or sex, though. The site’s owner says that, based on 2,656,058 clicks recorded thus far, the average (median) reaction time is 215 milliseconds. But some people can regularly post times of 130ms. This test not only rejects clicks that jump the gun (before the signal is given), it only counts data of 100ms and above, in order to avoid skewing the data with “lucky clicks”, when someone’s brain issues an order to click before seeing the signal but then the signal occurs just before their finger performs the movement.

Let us marvel for a moment at the process, which involves multiple neurons structured like this.


Diagram from Wikipedia, where a larger version can be seen.

Communication within a single neuron is electrical, but that between neurons is chemical, so neuron A has to make and release a chemical to pass a message on to other neurons.


A signal propagating down an axon to the cell body and dendrites of the next cell. (Wikipedia)

And this is just the transmission part of reaction time. The processes involved in choosing an action…well, my neurons are boggled enough for one day.

Reading and the brain, and “brain scans”

There’s a new book out about what happens in our brains when we read, which may appeal to people interested in accessible accounts of neuroscience, as well as to those of us who are watching the shift from paper to electronic reading.

Reading in the brain : the science and evolution of a human invention
Stanislas Dehaene. (New York : Viking, 2009)
ISBN: 9780670021109 – Description: xi, 388 p. : ill., map ; 24 cm.


I put a reserve on it at the library and am waiting for it to arrive. In the meantime, I found that the author has put all the color figures online along with short chapter summaries. The imbalance on the webpage between text, and the diagrams and brain maps, makes the book look more forbiddingly technical than it is, I hope. Unfortunately the book on Amazon doesn’t have the LookInside feature, so we can’t look at more of the text. Reviews have been mostly positive (links to several, on author’s page; Barnes and Noble review) though one was critical of the book’s accessibility for us “interested lay readers”:

Unfortunately, he needs to lay a lot of groundwork. This makes the first 100 pages of the book an excruciating slog. While it picks up after the first two chapters, the book still sometimes slips back into detailed explanations of neurophysiology. Dehaene is first and foremost an academic, and he seems to want to make his work defensible to his peers even as he tries to explain it to laymen. This is especially problematic in his diagrams. Rather than helping to clarify points, his visual presentations are almost always overly technical, presenting formulas and pictures of the brain that are difficult to decipher. Part of the problem is that images are all black-and-white. While he offers up full color versions on the book’s website, that’s only useful to readers who are also regularly consulting their computers. …The result is a work that requires focus to read, but rewards the effort.

It is disappointing that, according to this reviewer, the images in the book are not in color like those on the web. This reminds me of a book I looked at recently on the various branches of our early human-ish ancestors, in which maps to locate the various hominid species were poorly done or not there at all. Publishers try to cut corners and end up crippling the book. But I hope that won’t be the case here, and even if parts of it are over my head I look forward to the exploration.

I’m expecting a stimulating mix of actual established neuroscience, conclusions based on new research still open to interpretation, and informed speculation. After discussing how, he believes, reading (including our writing systems) developed in response to our neurological structures—“over time, scribes developed increasingly efficient notations that fitted the organization of our brains”, Dehaene applies the same theory to other areas of human culture: “Mathematics, art, and religion may also be construed as constrained devices, adjusted to our primate brains by millennia of cultural evolution.”

Cautions about fMRI (brain scan) studies: What a fish can tell us

I don’t know how much of Reading in the Brain relies on fMRI data, but many of the popularized “this-is-how-your-brain-works” revelations do rely heavily on brain scans, including fMRI, and we’re seeing some push-back from other scientists. A study at Dartmouth (reported by Wired, and Science News) found that a salmon’s brain had “a beautiful, red-hot area of activity that lit up during emotional scenes [photos put before the salmon’s eyes]”. Wow! Unfortunately for all but the spiritualists among us, the fish in question was dead. Apparently the neural activity that showed up was random, and more rigorous statistical analysis of the data revealed this. While many popularizers, especially in the general media, give the impression that brain scan interpretation is cut and dried, the truth is quite the opposite.

Less dramatic studies have also called attention to flawed statistical methods in fMRI studies. Some such methods, in fact, practically guarantee that researchers will seem to find exactly what they’re looking for in the tangle of fMRI data. Other new research raises questions about one of the most basic assumptions of fMRI — that blood flow is a sign of increased neural activity. At least in some situations, the link between blood flow and nerve action appears to be absent. Still other papers point out insufficient attention to insidious pitfalls in interpreting the complex enigmatic relationship between an active brain region and an emotion or task. (Science News)

Michael Shermer, founding Publisher of Skeptic magazine and columnist for Scientific American, gives an excellent presentation of how fMRI works and why “bright spots” in the brain don’t necessarily tell us much of anything. His article (pdf) , “Five Ways Brain Scans Mislead Us”, is as technical as it needs to be but won’t give you a headache. A more technical but still readable article by Edward Vul et al., “Puzzlingly High Correlations in fMRI Studies of Emotion, Personality, and Social Cognition” examines one major source of errors in brain scan analyses. [There’s a short summary here at, if you want to skip the technical details, and an interview with Edward Vul at]

So while the area known as “social cognitive neuroscience” is fascinating, and we all love quick and easy explanations, remember that much of what you read in this area is, like the lottery, best used “for entertainment purposes only”.