A lot of things affect how well we take our medicine-how confident we are in the doctor, whether we've taken it before, and if it worked, or even if we expect it to work.

However, does what our medicine look like affect how well we think it works?

There's evidence that the color of a pill has a bearing at least on our perception of how well it performs. Many studies have shown that blue and green are felt to be calming. Red, yellow, and orange, in contrast, are associated with a stimulating effect.

In one study, scientists selected a group of volunteers, and told them they would be given either a stimulant or a sedative, but not specifically which they were receiving. In reality, they all received placebos, or dummy pills. Some were given blue pills, the others took pink ones. Remember, that blue is calming, and pink is stimulating.

Seventy-two percent of the volunteers who took the blue placebos reported getting sleepy. Only thirty-seven percent of those who took the pink placebo pills said they got drowsy. More generally, this study found what many others had before it, that often what you expect is what you get.

What this means to us is that confidence in our doctor, past positive experience with a medicine, and even the subtle association of a medication's color with the desired effect, might all combine to make it more likely that we will take the medicine as prescribed.