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Research on goal striving from the late 1980s and 1990s found that intentions account for only about 20 to 30 percent of the variance in actual behavior. In 1999 psychologist Peter Gollwitzer proposed implementation intentions, plans phrased as when situation X arises, I will perform response Y, in place of abstract goal intentions. The episode explains the phase model of action, which separates the deliberative, pre-decisional mindset from the implemental, post-decisional one, and stresses that if-then plans work only for people already committed to a goal. The mechanism, called strategic automaticity, primes the brain to notice a cue and trigger a planned response without drawing on willpower.

Field studies show the effect. Voters walked through a plan over the phone turned out at higher rates, employees who wrote down a date and time got more flu shots, and dieters doubled their weight loss. A 2009 study showed spider images to participants and found only those using an if-then plan reduced fear and disgust, and a 2008 study described goal shielding against intrusive thoughts. The approach has a limit: research by Theodore Powers and colleagues found it can hurt performance for people high in socially prescribed perfectionism.

• Voters guided to plan the time, starting place and prior activity were 4.1 percentage points more likely to vote.
• At a Midwestern company, a blank space to write a flu shot date and time raised vaccinations by four percentage points.
• In a breast self-examination study, 53 percent of the goal-only group followed through compared with 100 percent of the if-then group.
• Over two months, women using if-then eating plans lost 4.2 kilograms versus 2.1 kilograms for those attending group meetings.
• Competitive tennis players used if-then plans to block distractions during matches.