A Staff Report from the Straight Dope Science Advisory Board

If Flatworm A eats Flatworm B, will it absorb Flatworm B's  knowledge?

July 18, 2002

Dear Straight Dope:

I recently read Phantoms by Dean Koontz and was curious about his description of the "flatworms in a maze" phenomenon--namely that a flatworm can be taught to negotiate a maze and then ground up and fed to a flatworm that has never seen the maze. This new flatworm will absorb the knowledge of the maze from the first flatworm. At first I dismissed this as pure fiction, but then did a quick search on the net. It turns out that it is a fairly heavily discussed topic.  Rather that spend hours poring over poorly designed web pages, I thought I'd ask: has it been proven that memory or knowledge can be transferred through food? If so, what could the science behind it possibly be?

In that particular case, it's called "contamination" (also, I suppose, "wishful thinking"). The explanation for these experimental results is simple: if you don't fully clean the maze between trials it leaves traces of food odor. The second flatworm only has to follow the scent, plus the chemical trail left by the first flatworm, in order to find the food. You can get identical results by feeding the second flatworm a bit of the same food that's at the end of the maze.

However, the original experiments on flatworm learning (probably the basis for the book comments, horribly distorted from the actual data) did not involve a maze, but rather a Y-shaped trough: when a flatworm reached the fork, the experimenters gave it a shock to induce it to turn to the right-hand fork. They kept track of how long it took the worm to learn to go right every time. Then they promptly chopped up these trained worms, fed them to untrained worms, and found the new worms learned the same trick faster, and that there was something in the RNA of the trained worms that was facilitating this. There was (and continues to be, I suppose) some serious debate as to what exactly was going on here.  But the most conservative hypothesis is that a worm that has been actively learning has some sort of induced biochemical changes that reflect this process, and that by feeding a piece of tissue from a flatworm in "learning" mode to a flatworm not in such a mode, you induce a state of learning-readiness in the second worm by getting those distinctive chemicals into its tissues. In other words, instead of memory transfer, think of it as a "smart drug"--a chemical from a flatworm that has become smarter can make another flatworm smarter, but that's as far as it goes.

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