Winner and loser effects in humans: evidence from randomized trials

In many animals, contest winners are more likely to win subsequent matches while contest losers tend to lose their later fights. Such winner and loser effects can have long-lasting impacts on individual behaviour and fitness. Recent observations suggest that winner and loser effects may occur in humans, and we thus critically tested this proposition in two experiments involving video games and reading comprehension. We randomly assigned human participants to either win or lose in phase 1 by manipulating their task difficulty. Then we tested their performance in phase 2, which was moderately difficult for all participants. In both experiments, randomly assigned phase 1 winners performed significantly better in phase 2 than did randomly assigned phase 1 losers. The effect size was higher in the video game experiment than in the reading comprehension test, perhaps because the former involved an overt contest with one winner and one loser. Finally, men and women exhibited similar magnitudes of winner and loser effects. Our experimental approach as well as further critical experiments with humans can help us better understand winner and loser effects in general as well as their possible important influence on human performance.