What’s most helpful for improving performance – precise or vague information?

How precise does feedback need to be in order to support behaviour change? Most of us prefer exact information and are adverse to ambiguity (1), but absolute values may not be as successful for supporting behaviour change as one might expect according to a paper by Mishra et al. (2). The authors propose that less precise information allows individuals greater flexibility in interpreting feedback. The ability to distort information in a manner that is favourable to us in turn leads to expectations of a positive outcome. The authors further argue that this anticipation of success generates a placebo effect, enhancing performance.

To test their hypotheses, Mishra et al. conducted a series of three studies to address several key questions:

  • how does precise information (an exact value) versus vague (a range of values) affect both an individual’s expectation of the outcome and the actual outcome?
  • does restricting an individual’s ability to interpret vague information alter the outcome?
  • does motivation influence the effects of precise versus vague information?

Ambiguous is better: in the first study, participants were given a piece of chocolate (all the same size) and told that 1 gram of cocoa improved mental performance. One group was told the chocolate they received provided exactly 1 gram of cocoa. The other group was told it contained between 0.5 – 1.5 grams. To answer the first question, subjects rated how much they thought the chocolate would help them perform on a mental test (playing a game of Brain Age on Nintendo DS). Those that were told the cocoa content as a range had higher expectations that the chocolate would improve their performace, compared to those told a precise cocoa value. A different group of participants completed the mental challenge after being provided the same information as the first group. Those who were given the imprecise information improved the most from a baseline score (established for each individual before they were given the chocolate).

The researchers followed up using a similar protocol to investigate how restricting participants ability to interpret vague information influences performance. Priming one group of participants by asking them to “describe a situation in which you took great care to collect information and made a very careful, unbiased and accurate decision” eliminated the improvement in performance that occurred in the group given the range of values.

Perhaps not surprisingly, motivation affects how we use feedback. In a separate study, the authors examined how motivation to lose weight influenced actual weight loss when participants were given either precise or vague information about their progress. Mishra et al. created a fictional health index. Subjects came in once a week for three weeks to have their body weight and hydration measured. After being measured, subjects entered the values at a computer  station and were given individualized results. One group was given a precise value while the other was given a range in which one number was 3% higher and the other 3% lower. Each subject received information on how their results compared to the “healthiest” values of the index. After three weeks, those who were given a range of values and had the greatest motivation to change (e.g. numbers farther away from being healthy) lost the most weight. Those with high motivation, but a precise score, were less likely to lose weight. Those with low motivation (already within the healthy range), were less likely to lose weight, regardless of if they receive precise or vague information.

Vague information is more malleable – it can be distorted more easily, and we tend to distort information in a manner that is favourable to us. What does this mean for making healthy lifestyle choices and for weight management? Perhaps our desire for exact information backfires on our attempts to better ourselves. Allowing ourselves the opportunity to interpret feedback flexibly may enable more successful behaviour change. Is this related to our perceived complexity of the challenge of achieving and maintaining a healthy weight or our capacity to manage the challenge? Knowing the precise number of kilocalories consumed may seem appealing to some, and perceived to be the best way to track energy intake as accurately as possible.  However, this research suggests that a photo of the food we consume, a vague estimation of energy intake, may be more beneficial in encouraging us to change our habits.


1. Camerer C, Weber M. Recent developments in modeling preferences: Uncertainty and ambiguity. Journal of Risk and Uncertainty. 1992;5(4):325-370. Available at: http://www.springerlink.com/content/gh7822u5305v1010/

2. ResearchBlogging.orgMishra H, Mishra A, & Shiv B (2011). In praise of vagueness: malleability of vague information as a performance booster. Psychological science, 22 (6), 733-8 PMID: 21515738

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