Log or Linear? Distinct Intuitions of the Number Scale

Stanislas Dehaene, Véronique Izard, Elizabeth Spelke, and Pierre Pica. Log or linear? Distinct intuitions of the number scale in Western and Amazonian indigene cultures. Science, 320(5880):1217–1220, May 2008.

The Mundurucu are an indigenous culture whose language does not contain exact words for numbers above 5. Dehaene, Izard, Spelke, and Pica basically gave subjects an empty horizontal line and then gave them a bunch of numbers and told them to place the numbers where they belong on the line (the line was not entirely empty; the left and right hand sides were labeled with a small number and a big number).

Western adults tend to place the numbers linearly, whereas the Mundurucu tend to place them logarithmically. Western children also place them logarithmically, and even Western adults place them logarithmically if the numbers are presented as larger numbers of dots (10-100) or if they are presented as tones.

This suggests that there is an innate logarithmic representation of number which is used to populate the number line, but that with training a linear representation can be created.

New Yorker article on number sense

From March. Actually, the topic of the article is Dehaene, but it talks about some studies too. Excerpts after the break, interspersed with hyperlinks to citations that I looked up.


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Psychophysics experiment is bad news for deer

Findings: Tapping Into What a Deer Sees, and Doesn’t

Not being a hunter, I’m not sure how much I support this, but I must admit this is at least a very interesting application of psychophysics data. Using deer as subjects in a standard battery of visual psychophysics tests, researchers have engineered a new material/pattern (“Gore Optifade”) that is superior to standard camo for evading detection by deer. Looks like deer are red-green colorblind but have higher acuity in the blue end of spectrum than humans.

Once they had assessed the deer’s visual strengths and weaknesses, Dr. Neitz and Dr. O’Neill worked out colors, textures and shapes with Guy Cramer of HyperStealth Biotechnology, a company that designs military camouflage. Mr. Cramer’s computer algorithms create fractal patterns that exploit a couple of ancient tricks used by animal predators.

The first and most obvious trick is to fade into the background, as a leopard’s spots enable it to do while it’s patiently waiting to ambush a prey. The spots aren’t shaped like leaves or branches, but they form an overall “micropattern” matching the colors and overall texture of the woodland background.

That trick, though, won’t work for a predator on the move, which is why a tiger doesn’t have spots. It has a “macropattern” of stripes that break up the shape of its body as it’s stalking or running.

There is a nice demonstration image with the article showing the same scene viewed with human vs. deer vision.

Neuroscience of voting

As the first presidential debate nears, there’s a lot of excitement (and worry) regarding the election. Today, Salon had an interesting piece on voter behavior and irrational attachment to ideologies and candidates. Recounting a recent psychology paper’s punchline:

The article’s conclusion should be posted as a caveat under every political speech of those seeking office. And it should serve as the epitaph for the Bush administration: “People who lack the knowledge or wisdom to perform well are often unaware of this fact. That is, the same incompetence that leads them to make wrong choices also deprives them of the savvy necessary to recognize competence, be it their own or anyone else’s.”

Slate had a story (“Why is every neuropundit such a raging liberal?“) about how neuroscience and neuromarketing are changing political consulting (also here’s a link to a similar story in NYT last week):

According to a study of political psychology published last Thursday in Science, conservatives tend to be the jumpier lot.

The researchers called 46 political partisans into their laboratory at the University of Nebraska, affixed electrodes to their fingertips and eyelids, and measured sweat output and eye blinks in response to a series of startling stimuli. (Subjects were forced to endure images of bloody faces and maggot-infested wounds, as well as sudden blasts of white noise.) The results: Social conservatives—those who supported the death penalty, the Patriot Act, prayer in school, and the like—sweated more, and blinked more intensely, than the liberals.

The Slate and NYT articles in particular suggest something that I have long believed to be true. The Republican “story” is, from a neuroscience perspective, simply better because it tends to view the world in clear-cut terms with no middle ground and, thus, is more effective at rallying emotional processing areas of the brain (eg. limbic system). It is well-known in neuroscience that emotionally salient events that activate these limbic structures are better remembered than less charged memories. The Democratic “story” tends to be more complicated with shades of gray and therefore requires higher-level processing (eg. cortical areas involved in conflict resolution). Clearly, I’m oversimplifying things here a bit (see, I’m designing this post to appeal to your limbic system!) but I think that this hypothesis might have some legs.

Of course, if it’s true, why doesn’t everyone vote Republican if that story is the neurally more rewarding one? Or perhaps the more relevant question: Is it even possible for the Democrats to tap into the similar evolutionarily older limbic structures that seem to dominate the Republican story?

Also, although I prefer Neurodudes to stick with the science over any partisan politics, I must say I found this statistic interesting (from the Slate article):

in 2002, Daniel Klein and Andrew Western tallied the political affiliations of professors at Berkeley and Stanford and found that even in the hard sciences, Democrats outnumbered Republicans by a factor of almost 8 to 1. Among professors of neurology and neuroscience, Klein and Western counted 68 registered Democrats against just six Republicans.