Why do specific goals beat 'just do your best'?

Mostly because a vague goal gives you nothing to aim at. Decades of research by the psychologists Edwin Locke and Gary Latham found that specific, difficult goals lead to markedly better performance than easy goals, no goals, or the classic 'just do your best'. As long as people accept the goal, have the ability to reach it and don't face conflicting goals, the harder the goal, the higher the performance.

Locke got the idea from Aristotle, who speculated that purpose can cause action, and published his first paper on it in 1968. By 1981 he and his colleagues could report that 90 percent of studies found specific, challenging goals beat easy or absent ones. 'Do your best' fails, Locke and Latham argue, because it has no external reference: you can never tell whether you've met it.

But goals have a dark side. When Lee Iacocca demanded a Ford that weighed under 2,000 pounds and cost under $2,000, on a tight deadline, safety checks were skipped and the resulting Pinto's fuel tank sat just 10 inches behind the rear axle; fiery rear-end crashes caused 53 deaths. Sears gave its mechanics a target of $147 per hour, and some began overcharging customers and doing unnecessary repairs. A team led by Lisa Ordóñez and Maurice Schweitzer called this 'goals gone wild'.

Lab studies agree: specific goals made people more likely to overstate their results when they fell just short. Goals work best for routine, measurable tasks, and when a task needs skills people don't yet have, a learning goal works better than a performance target.