Thursday, March 3, 2011

Physics and Biology: How's your aim?

This week we carried out an experiment to test the effects of using one eye or two eyes on depth perception. The kids were given a picture of a target superimposed on a charging rhinocerus.* The target was placed at a distance of 35 cm from the subject, and then he or she had to "shoot" the target with a marker, meaning try to draw a dot at the bullseye. Using different colors for the 3 conditions: both eyes, right eye, and left eye, we were able to score the shots. It was surprisingly difficult to hit the bulls-eye using only one eye, and even when subjects were successful, the kids observed that they were using other cues to compensate, for example how far your arm needs to be extended.

Afterward we did a little comparative anatomy, looking at a skull belonging to a human(we used our own), a horse, a wild bore, and a dog. We observed that in order for depth perception to work, an animal's two eyes must have overlapping fields of vision. We also related these anatomical differences to whether or not animals tend to be predators or prey. Of course, as one student pointed out, this only works when you're talking about animals that use vision in the first place - i.e. doesn't work for bats who hunt using their keen sense of hearing.

*No rhinos were harmed in this experiment

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