Good news and bad for a popular willpower-enhancing strategy

In rich countries, temptation is never far and many of us struggle to achieve our long-term aims of moderation, dedication and fidelity. An increasingly popular strategy for regaining control is to form so-called implementation intentions. Rather than having the vague goal to eat less or exercise more, you spell out when, where and how you will perform a given activity, and rehearse that thought regularly. For example, "when in the cafeteria at lunch I will buy orange juice rather than cola". A more specific variant is to form an 'if-then' plan, as in "if it is a Tuesday morning, then I will go for a run," and again, this is rehearsed mentally on a regular basis.

Past research has found these plans to be successful, helping people to live more healthily. There's even evidence that they are particularly beneficial to those who have had their willpower compromised by brain damage or by taxing laboratory tasks. Two new studies add to this literature, one of them cautionary, the other more hopeful.

Sue Churchill and Donna Jessop studied 323 students tasked with eating more fruit and vegetables. They found that implementation intentions helped students achieve this task over a 7-day period, but only if they scored low on a measure of "urgency", as revealed by their agreement or not with statements like "When I am upset, I often act without thinking." The researchers said this suggests implementation intentions may not be a panacea: "Ironically, people who possess poor self-regulatory skills insofar as they tend to act on impulse when distressed, who are arguably most in need of assistance in achieving their goals, may benefit least from behaviour change interventions based on implementation intention formation."

Why the contradiction with earlier research showing implementation intentions are most helpful to those with compromised willpower? Churchill and Jessop can't be sure, but they said one possibility could be because their task of eating more fruit and veg is more complex than some of the lab tasks studied previously.

That's the cautionary news. The good news comes from a study by Barbel Knauper and her colleagues who found that using mental imagery boosted the benefit of implementation intentions for students attempting to increase their fruit consumption over seven days. Rather than merely forming an if-then plan, such as "If I see orange juice at lunch, then I will buy it", they also imagined themselves performing this act, with as much sensory detail as possible. A promising result, and the researchers expressed their surprised that no-one had thought to investigate the combination of these two strategies before.

Here's a curious observation across both studies. Knauper's team failed to find the usual benefit of forming simple implementation intentions (without the addition of mental imagery) and her team said one possible explanation for this was the simplicity of their task of eating more fruit. Recall that Churchill and Jessop thought the same task (admittedly, also including vegetables) was relatively complicated compared with tasks used in earlier research. It just shows how much room there is for interpretation.

Both studies suffered from a reliance on retrospective self-report - the students told the researchers whether they'd managed to eat more fruit and veg or not over the preceding week. They also had short study durations - we need our newfound healthy habits to last longer than a week. But together the studies point to some interesting avenues for future research. Perhaps implementation intentions plus imagery will prove to be effective for people who have particularly weak willpower?
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S Churchill, and D Jessop (2011). Too impulsive for implementation intentions? Evidence that impulsivity moderates the effectiveness of an implementation intention intervention. Psychology and Health DOI: 10.1080/08870441003611536

B Knauper, A McCollam, A Rosen-Brown, J Lacaille, E Kelso, and M Roseman (2011). Fruitful plans: Adding targeted mental imagery to implementation intentions increases fruit consumption. Psychology and Health DOI: 10.1080/08870441003

This post was written by Christian Jarrett for the BPS Research Digest.