The power of suggestion may be stronger than previously believed. Our expectations influence behavior as well as performance, product preference and treatment response.

Suggestion can play some clever tricks on people. Horror movies are great examples of this. As you watch a climactic scene where the tension is building and eventually you think something is going to pop out of the closet that the main character is opening. It turns out nothing is in that closet but you still jump thanks to your expectations.

Science also experiences a similar response to expectations that you may be familiar with; the placebo effect. Patients may receive a pill that has no treatment power but are told it does and they may in turn experience some positive benefits thanks to something that has no real power.

This wide sweeping power of suggestion has led Maryane Garry, PhD, and Robert Michael, PhD, from the Victoria University of Wellington and Irving Kirsch, PhD, from the Harvard Medical School to look at previous studies involving people's expectations. According to the researchers, the power of suggestion causes "response expectancies" in people. This expectation plays a huge role in the actual outcome of the experience.

Researchers give an example of a shy partygoer who believes that a glass or two of wine will let them relax and enjoy the party. Throughout the party, the once shy partygoer is now a social butterfly, engaging in conversations with strangers and being less inhibited. The shy person may believe the wine was the reason behind this metamorphosis but, according to researchers, the person's expectation of what the wine would do to their behavior also played a large part in that outcome.

The power of suggestion can also hold sway when developing new treatments. The observational effect of researchers can cause participants to work harder or work on something for longer. Instead of the drug or treatment being totally effective, the participant may be altering their behavior based on observation or feeling special due to the increased attention.

Those same trials also put the researchers at the risk of falling to the power of suggestion as they could lead participants to support the proposed hypothesis of the study.

Further, the power of suggestion can affect the criminal justice world. If a lineup is set up by someone who knows who the suspect is that individual may tailor the lineup, unconsciously, so a witness would pick the suspect. The researchers cite the higher rate of false identification when someone who previously knew who the suspect was set up the lineup when compared to a lineup set up by someone who did not know who the suspect was.

Suggestion is also powerful in education. Dreading a big test could cause your performance to suffer because when you settle in for the test, you believe it will be difficult which could affect your memory and recalling information.

Researchers hope to develop future studies dissecting the power of suggestion, including how powerful it really is. Understanding expectations can affect daily life as well as possibly improve the testing of new drugs.

The study was published in Current Directions in Psychological Science.