The cues, according to Nitschke, were flashed to subjects just prior to the administration of a few drops of liquid. But in the study, the cues would not always match the taste they were said to presage.
His group observed that when subjects were given a cue that suggested the taste they were about to experience would be less bitter, the taste was perceived as such, and the regions of the brain that code tastes were activated less.
"When the subject sees the warning signal, portions of the brain activated by the misleading cue predict the decreased brain response to the awful taste," Nitschke says. What's more, "the (brain's) response to the misleading cue will predict the subject's perception of what the taste is going to be. The subject anticipates that the taste won't be that bad, and indeed that's what they report."
In short, the new study shows how expectancy affects how humans perceive sensory input, and how events in the brain are directly related to those perceptions.
Importantly, by mapping how the brain anticipates an event and kicks in a placebo effect, Nitschke argues, scientists can begin to think about ways that knowledge could be used in clinical settings.
For Nitschke, who also practices as a clinical psychologist specializing in the treatment of depression and anxiety disorders, the new detailed insights into the power of anticipation could lead to better treatments for such conditions.
"The placebo operates through expectancy. In this study, we've taken the pill out of the picture. We're just manipulating expectancies," he says. "The results beg the question of what can we do to target anticipatory processes in our patients that might lead to better outcomes."