Our memory of time is shortened when we believe products and events are related

When we believe two events are connected -- such as drinking caffeine and getting a burst of energy -- we tend to compress time, according to a new study in the Journal of Consumer Research.

"People sometimes feel the effect of product consumption almost instantaneously—within an unrealistically short time after consumption," writes author David Faro (London Business School). "Such placebo-like effects are typically attributed to conditioning, wishful thinking, or expectations about product efficacy. The present research shows such effects can also occur because, under some conditions, people are prone to underestimate the time-to-onset of products they have used in the past."

In one of the author's experiments, participants first listened to music and later took part in a creativity task. Half of the participants were then told the music they had listened to earlier enhanced creativity; the rest were not given that information. "When asked to recollect the amount of time that elapsed between listening to music and the creativity task, the first group thought that the time was significantly shorter," Faro writes. "Hence, even though both groups had (on average) the same experience with the music and with the creativity task, believing that the two things were related made participants connect them more closely in time."

In a second experiment, participants first chewed a stick of gum and then took part in an attention-related task. Later in the study they were told that chewing gum increases attention. In that case, participants who considered only the gum as a cause for increased attention gave shorter estimates of time-to-onset than other participants who also considered another contributing cause: practice with the task. On a later occasion, the participants said they experienced the gum's effect earlier and they were less interested in trying a competing product.

"These experiments show that our recollections of how long products took to have an effect on us when we have used them in the past are intertwined with our beliefs in their causal role," the author concludes.