When you row a boat and slack one oar the boat turns toward the side on which you are expending more effort. Of course the process is reversed in a dog because the nerves of the dog cross over, the right side of his brain supplying the left side of the body, the left side of the brain supplying the right side of the body with power. Let us repeat on two dogs, the experiment which academic psychologists imagined performed on a mythical jackass. =The Dog's Choice.= Offer two pieces of meat to a dog whose brain has been injured on the right side and he will invariably eat the piece of meat nearer that side. Repeat the test on a dog whose brain has suffered a lesion on the left side and you will see him gobble the piece of meat on the left side. Go even further and place both pieces of meat on the left side of the dog injured on the left side of his brain and he will "pick out" the one farther out. Not that he "prefers" that one. He will aim at the nearest but his injury will cause him to deviate too far to the left and he will be unable to reach the nearest one. Other experiments on dogs illustrate the purely organic "motives" back of certain lines of conduct. When both sides of a dog's brain have been injured in the frontal region, the dog refuses to go forward or downstairs but has a tendency to move backwards and to run upstairs. When the back of a dog's brain has been injured on both sides, the dog has a tendency to keep on running forward all the time and while he is unwilling to climb stairs he will willingly go downstairs. =The Behavior of Copepods.= When we pour carbonated water or beer or alcohol into an aquarium, certain crustaceans called copepods will at once swim toward the source of light, as tho they "loved" light, and appear so interested in light that they will "forget," to eat their food, if that food is placed away from the source of light. The same animals when placed in water containing strychnine or caffein, will shun the light as tho they "hated" it, and as tho they "loved" the darkness. We know that if a galvanic current is sent thru our head we will lean involuntarily against the positive pole. If the current is sent thru an aquarium, a number of the animals swimming in it will be compelled to seek the positive pole and to remain there, others to seek the negative pole. In the case of the laboratory dogs, a permanent modification of the nervous system caused a permanent modification of the animal's behavior, which could not be "cured," (for brain injuries do not "heal," the cells of the brain being unable to reproduce themselves), but which would probably be compensated for by gradual adaptation. In the case of the "phototropic" or "galvanotropic" animals, the modification of the nervous system was only temporary but might cause a more or less durable modification of the animals' behavior, if allowed to last a considerable length of time.