Biological preparedness refers to the fact that certain associations are learned more readily than others due to a species' evolutionary history. This was first demonstrated by American psychologist John Garcia in 1966 in what is now considered a classic experiment. The research involved two groups of rats that were allowed to drink saccharine-sweetened water while lights flashed above them. One group then received an electric shock while the other was irradiated to make them feel nauseated. The rats that had been shocked would not drink when the lights were flashing but willingly drank saccharine-sweetened water when the lights were not flashing. In contrast, rats made to feel nauseated would not drink the saccharine-sweetened water under any circumstances. However, they would drink plain water whether the lights were flashing or not. The rats had no experience of the outside world, yet they were biologically prepared to link electric shock with flashing lights and nausea with new flavors. This Garcia effect has been demonstrated in numerous species, including humans.
A taste aversion is an intense dislike of a particular food or liquid, often forming after a single exposure to a novel taste. For example, chemotherapy makes patients feel nauseated. If they eat a food they've never eaten before around the time that they receive chemotherapy, they may develop a strong aversion to the novel food.
Common phobias also show the impact of evolutionary history. Humans are far more likely to form phobias toward stimuli that threatened survival over evolutionary time. It is much easier to develop a phobia of spiders or snakes than a phobia of electrical outlets or guns.
Mirror Neurons and Observational Learning
A mirror neuron is a nerve cell that fires both when performing an action or when observing another perform that same action. Mirror neurons are located throughout the brain in the frontal, parietal, and temporal lobes. This circuitry enables imitation, language learning, and empathy.
Mirror neurons were discovered in the frontal lobes of monkeys by Italian neuroscientist Giacomo Rizzolatti in the 1980s. Rizzolatti and his team were studying brain activity using implanted electrodes while monkeys performed activities such as reaching for a peanut. Researchers noticed that when monkeys watched them reach for objects, the same neurons became active as when the monkeys reached for objects themselves. Using similar techniques, they and other research teams discovered mirror neurons that activate both when monkeys experienced emotions and when they observed the same emotions in others.Similar results were discovered in humans using noninvasive techniques such as brain imaging. In one study, the brains of participants were imaged while they inhaled unpleasant odors (such as rotten butter) and as they viewed a film of an actor who wrinkled up his face in a disgusted look. The researchers found that feeling disgusted and watching someone else look disgusted activated the same region of the olfactory cortex, which processes odors. In another study, researchers found that the same area of the somatosensory cortex was active both when participants were lightly touched on the leg with a feather duster and when they viewed pictures of someone else being touched in the same spot with the duster. Mirror neurons may play a role in helping humans learn, understand the intentions and emotions of others, and copy the movements of others. However, research on motor neurons is in the early stages, especially in humans. Many researchers express doubts about whether mirror neurons play a significant role in human learning and understanding.