Wednesday, September 5, 2012

Seeing Red: Why elephants might dislike the vision-based studies of their primate peers

If you aren’t familiar with the story of the blind men and the elephant, here’s the gist:

Six blind men receive word that an elephant is in their village. They have absolutely no understanding of what an elephant is, and being blind, decide to investigate by feeling it. Each of the men approaches and touches a different part of the elephant… a leg, a tusk, the trunk, etc. Consequently, each comes away with a different understanding of what an elephant is like; and they begin to argue about who is right. By and by, a wise man passes through and explains that they are all right but that each of them is only “seeing” a fraction of the whole truth. In some versions, the six men not only stop arguing but begin to work together to gain a more comprehensive understanding of the elephant.

Photo Credit: Public Domain

Many morals can and have been drawn from this parable, but I want to talk about what this parable has to say about scientific research. 
Here’s what we can learn:

When you want a research subject to obtain a full understanding of a novel task, you need to be able to give the subject adequate information. What the six blind men tell us in the “elephant experiment” set before them is that, if you do not provide information to the subject through a primary mode of sensory perception, you’re bound to end up with confused interpretations.

Of course I can’t blame these six fictional men for being blind. So, let’s say instead that the subjects are not blind, but the experimenter decided not to give them visual contact with the elephant and instead provided them with only tactile information. Perhaps the experimenter gets all of his information through touch and, assuming the same of the subject, felt satisfied that he had provided adequate information to the subjects in the elephant experiment. The experimenter’s assumption leads him to misinterpret the result—that no one subject was capable of fully understanding the elephant—as a reflection of the subjects’ inadequate capabilities rather than a reflection of the inadequacy within the experimental design.

It’s kind of hard to imagine a being that gets all of its information through touch, so let’s substitute ourselves—highly visual humans—into the experimenter position. And while we’re at it let’s make the elephant the subject and the experiment about food. In this reality, the human experimenter assumes that it is sufficient to provide an elephant with visual information regarding the presence of food in an experiment. This is not a safe assumption to make when studying a species with a sense of sight that is likely to be far inferior when compared to that of humans and most other primates.

Humans are trichromatic. We have three types of cones in our eyes, one serving as a color receptor for red, one for blue, and one for green.

Anatomical evidence from the elephant eye suggests that elephants are dichromatic. Much like dogs, they only have cones for blue and green.
They cannot see red.

This inability doesn’t just mean that they miss out on one color but the vast multitude of pigments we get by mixing red with green or with blue in a wide range of ratios. Add on top of this, an apparent sensitivity to light contrast, and you have a species which relies upon its vision to the extent that we might rely upon our sense of smell.

Again, this scientific knowledge of elephant vision is speculative and stems purely from their anatomy. Actual tests for color vision are not easy. They require tightly controlled digital technology and a setting that offers consistent lighting. You can’t simply hold up various colored swatches in front of an elephant and reward them for picking the blue swatch under the assumption that they have to be able to see the color differences before they can start to favor the one that gets them food. Most of the time, you can actually discriminate between colors without having color vision at all.
For example, look at the colored squares below:

The pigment difference between these squares makes it easy to tell them apart.
Now, here are the same three squares reproduced in grayscale:

As you can see, other qualities of color beside pigment—hue, value, saturation, etc.—could serve as potential loopholes in the experiment, allowing even the dichromatic eye to pick the blue square.

But regardless of whether elephants can actually see red or not, they have every right to be frustrated when vital experimental information is not provided to them in a recognizable or appropriate fashion. We can’t count on a wise man to come strolling by and drop helpful hints to our elephants. Instead, it’s crucial that researchers see/hear/smell the world through the eyes/ears/noses of their subjects if they want to give the subject the greatest chance of success.

And THAT’s the story of the blind men and the elephant.

No comments:

Post a Comment