As we've seen, however, the brain has many ways to make good on our expectations, both good and bad. In response to a clinician's promise, the brain releases painkillers as strong as morphine. Anxiety short-circuits anticipation and the athlete's worst fears come true. The embodied expectations of looking powerful can send our hormones racing. As Ader's saccharin-slurping rats demonstrated, the immune system can be ratcheted up and down without a word being said.
We saw in Chapters 6 and 8 how readily we take cues for our own behavior from watching others. Why couldn't placebo and nocebo effects spread socially, too? In 2007, for a rare lab study of nocebo contagion, psychologists at the University of Hull (UK) somehow recruited 120 people to test "individual reactions to environmental substances." The researchers gave everybody an inhaler that supposedly contained a toxin known to cause headaches, nausea, itchy skin, and drowsiness. In reality, the inhalers contained nothing but plain old air.
Each subject was paired with another subject who was actually an actor in cahoots with the researchers. Sometimes the actor would show symptoms, either by answering the researchers' questions or by wincing, yawning, or throat clearing, and so on. In other cases, they'd stay symptom free.
Isolated in a room, the pairs of participants were told to inhale the toxin and then to hold their breath for three seconds. Over the next hour, a researcher checked in every ten minutes to see how they were feeling. They always spoke to the confederate first, and asked about the four symptoms mentioned up front and four other unexpected symptoms— watery eyes, scratchy throat, tightening chest, and difficulty breathing. Subjects whose partners displayed phony symptoms felt sicker and reported significantly more symptoms than subjects whose partners seemed unaffected by the "toxin."
Placebos can also be contagious, as Benedetti and his colleague Luana Colloca demonstrated in 2009. Subjects enduring painful electric shocks to their hand experienced placebo pain relief when a green light on the machine delivering the shocks was illuminated and felt more pain when the light was red. They weren't told what these lights meant —in reality, they meant nothing— but they'd watched another subject, actually a confederate of the researchers, faking his way through the red and green light shocks. Notably, the placebo pain relief was much stronger for these folks than it was for another group of subjects who were told up front what the lights meant but were given no demonstration.