Recent research on placebos gives us clues about the mechanisms by which our mental activity causes these effects. In a conceptual replication of earlier work, Antonella Pollo and colleagues asked people to lift a certain amount of weight before and after drinking caffeine at high doses. The liquid in fact contained no caffeine, but the weight was secretly reduced after people drank it. That way, people learned to associate the liquid with less fatigue. Later, when people lifted the original weight after drinking the liquid, they experienced less fatigue. It seems that a central neural governor of fatigue suppressed the fatigue response. Marion Goebel and colleagues gave allergic patients allergy medication after a novel-tasting liquid. Later, drinking the liquid with fake medication suppressed the immune system and allergic skin reactions. Fabrizio Benedetti and colleagues first increased people’s growth hormone levels by injecting medication. Later, injecting a saline solution (salt and water) presented as medication resulted in similar increases in hormone levels. Predrag Petrovic and colleagues suppressed people’s emotional reactions to unpleasant pictures by injecting antianxiety medication. Later, injecting a saline solution presented as medication resulted in reduced activation in brain areas associated with anxiety.
Expectancies, such as expecting that one’s work will bring about health benefits, are capable of producing physiological outcomes. Learned associations, such as the association between being an Air Force pilot and having good vision, can alter other cognitive processes, such as visual perception. Meanwhile, placebo effects observed in clinical research work via expectancies and learned associations created by fake operations, sham drugs, etc. Such expectancies and learned associations have been shown to change the chemistry and circuitry of the brain. These changes may result in such physiological and cognitive outcomes as less fatigue, less immune system reaction, elevated hormone levels, and less anxiety. The interventions that resulted in better performance in a knowledge test or better vision are placebos outside of the clinical context. However, the chemical and neural mechanisms by which they operate are probably similar.
These are likely manifestations of an adaptation that helped us survive throughout our evolutionary history by helping us prepare for the future. For example, when subtle cues in an environment trigger thoughts about a predator, that in turn triggers physiological changes that prepare the body for the impending confrontation even before the predator comes into sight.
If mindsets can change us, maybe we can deliberately choose our mindsets to improve our abilities. We can choose to adopt a mindset that improves creativity, for instance. People who think of categories as flexible and actively focus on the novel aspects of the environment become more creative. Ellen Langer and Alison Piper introduced people to familiar or unfamiliar objects conditionally or unconditionally. If an object, say a dog’s chew toy, was introduced unconditionally, its description simply read, “This is a dog’s chew toy.” When the dog’s chew toy was introduced conditionally, its description read, “This could be a dog’s chew toy.” When an object is introduced conditionally, it is categorized flexibly; and it is easier to focus on the aspects of an unfamiliar object without preconceptions. When people were asked to solve a problem that required creative use of available objects, only people who were introduced conditionally to unfamiliar objects could solve the problem.