Forbidden Flavors: Scientists Consider How Disgusting Tastes Can Linger Surreptitiously in Memory
Bower, Bruce, Science News
John Garcia relishes the story he heard as a child about how his mother came to detest that most vaunted of sweets, chocolate. Just before taking a boat voyage at age 3, she contentedly ate several chocolate candies. While on board later that day, she became terribly seasick and vomited. From then on, she found the taste of chocolate abhorrent, even though the grown-up Mrs. Garcia knew that chocolate treats do not cause seasickness.
Working on farms and ranches in Northern California as a youth, Garcia heard more stories of food aversions caused by illness-these occurring in a different corner of the animal world. If a coyote or other wild creature eats poisoned bait and survives, the budding scientist was told, it never again picks up bait. As a result, older predators prove nearly impossible to kill with standard baits.
It seems fitting, therefore, that Garcia's more than 40-year career in psychology has revolved around the study of such taste retreats. He refers to the behavior as conditioned taste aversion, but many animal investigators call it simply the Garcia effect.
In brief, creatures up and down the food chain readily associate nausea or other bodily signs of illness with the taste of what they have most recently consumed. That flavor is then shunned, often after only the initial bad experience. What's more, the effect ensues with equal force whether nausea strikes a few minutes or many hours after a tainted snack or slurp.
Garcia's research sparked intense controversy in the 1960s and 1970s because it contradicted the basic tenets of psychologist B.F. Skinner's then-dominant radical behaviorism. Skinner held that general laws of learning shape the behavior of all animals, regardless of a particular creature's evolutionary history or biological makeup. In contrast, Garcia argues that an animal is a "biased learning machine" designed by evolutionary forces to forge meaningful links between some stimuli but not others.
According to Skinner's theory, food or any other reinforcing stimulus consistently made available after a random behavior-any act fancied by the experimenter-renders that behavior inevitable whenever the stimulus reappears. Pigeons trained to obtain food pellets by pecking at keys whenever a light above the keys was turned on came to symbolize the power of Skinnerian reinforcement.
Garcia, now 79 and a professor emeritus at the University of California, Los Angeles, presented an alternative view that has moved from the fringes to the mainstream of animal research. The confection rejection exhibited by Garcia's mother derived not from random learning but from evolutionary influences that yielded gut-level mechanisms for expelling poisons from the body. Skinner's pigeon experiments did not produce key pecking from scratch, Garcia contends. In hitting the keys with their beaks, the pigeons employed their natural feeding behavior-pecking at bits of grain or other goodies.
Russian physiologist Ivan Pavlov laid the foundation for current strains of taste aversion research. Getting hungry dogs to drool at the sound of a bell is one type of biologically based learning; taste aversion is another.
"I originally got into a lot of trouble in psychology for studying conditioned taste aversions, but this has become a broad and very exciting area of research," Garcia remarks.
The exploration of taste aversions has expanded to include efforts to ward off wild predators from livestock without killing the carnivores, to chart animals' social communication about food aversions, to explore hormonal sensitivities that may push some teenage girls toward self-starvation and anorexia, and to identify brain structures essential for tagging selected flavors as forbidden.
Garcia's research also inspires psychologists now investigating central realms of human knowledge and learning, such as categorizing local animals and plants (SN: 11/16/96, p. 308) and detecting people who cheat on mutually beneficial agreements (SN: 1/29/94, p. …