Biological Limits on Conditioning: Taste Aversion, the Garcia Effect & Instincts

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  • 0:03 Taste Aversion
  • 0:44 The Garcia Effect
  • 1:52 Instincts
  • 2:25 Lesson Summary
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Lesson Transcript
Instructor: Paul Bautista
How can biological influences affect conditioning? Have you ever had food poisoning? In this lesson, you'll see how natural responses can accelerate or hinder conditioning.

Taste Aversion

Is there a food that you won't eat anymore or a drink you can't stomach? For my husband, it's fish. In college, he spent a few months studying in Indonesia. Living on an island, he was given fish for breakfast, lunch and dinner. Soon after arriving on the island, he came down with dysentery, which caused him to feel achy and nauseous all the time. Although that was years ago, he still feels sick to his stomach whenever he eats something even vaguely fishy tasting.

You don't need to get sick from the same food more than once in order to develop disgust for it. There's an evolutionarily advantage to taste aversion, since it prevents us from eating something twice that might be toxic.

The Garcia Effect

Taste aversion was first noticed by psychologist John Garcia in the 1950's. He was irradiating rats to see its effect on their behavior, and noticed that rats didn't want to eat the things they'd been fed shortly before being irradiated. Garcia theorized that this was because they were getting nauseous from the radiation. He conducted experiments to directly test this with sweetened vs. unsweetened water: he gave them sweetened water followed by no radiation, mild radiation, or strong radiation. After the experiment, the total sweetened water consumed by non-radiated rats was 80%, mildly radiated rats drank 40% and strongly radiated rats drank only 10% of the sugar water. These patterns were observed after only ONE trial. The radiated rats were conditioned to link the taste of sweetened water with nausea and therefore avoided it. Since it accessed an evolutionarily-advantageous bodily defense mechanism, it was learned right away.

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