Worth a Thousand Words: Handedness in Fish

If you look closely at the image above, you’ll see that the mouths of these cichlid fish, Perissodus microlepis, curve in opposite directions. Similar to left or right handedness in humans, many animals exhibit handedness in behavior or morphology. Whether handed behavior is expressed early in development and produces mouth asymmetry or the opposite, that mouth asymmetry produces handed behavior, however, is not well known. The authors of the study “Handed Foraging Behavior in Scale-Eating Cichlid Fish: Its Potential Role in Shaping Morphological Asymmetry” set out to investigate this question and more.

Baby songbirds learn to sing by imitation, just as human babies do. So researchers at Harvard and Utrecht University, in the Netherlands, have been studying the brains of zebra finches—red-beaked, white-breasted songbirds—for clues to how young birds and human infants learn vocalization on a neuronal level.

While a baby bird mimicking the chirps of his “tutor” may seem far removed from human learning, the researchers at the two universities found that the songs of the birds and human language are both processed in similar areas on the left sides of the two very different brains. The discovery was published last month in the Proceedings of the National Academy of Sciences.