Goalkeepers should always dive on penalties — never stay in the middle.
Bar-Eli et al. (Journal of Economic Psychology, 2007) analysed 286 elite-league penalties and found goalkeepers saved about 33% when they stayed in the centre and roughly 12–14% when they dove left or right. They concluded the diving choice reflects an 'action bias' — keepers feel they look better having tried something, even when staying still is the higher-percentage play.
// sources1Action bias (Bar-Eli et al., 2007)
Busted33% vs 14%
Saves · centre vs dive
// verdictBUSTED