Are breaches of trust early in a relationship more harmful than later betrayals? On the one hand, we all know the power of first impressions. On the other hand, being crossed by a trusted comrade stings. Research indicates that, indeed, an early wrong is the greater offense and can permanently cripple a relationship, even after repeated displays of contrition.
Subjects made a series of decisions about whether to cooperate with or compete against a partner (secretly played by a computer). Players became angrier and rated their partner as less trustworthy when the computer competed on the first two turns, compared to later defection. These players also retaliated more during the final 10 rounds of the game, even though the computer never again defected.
If you can't avoid violating people's expectations—i.e., if you're human—take heed. "Say you're overbooked and you have to flake," says study co-author Robert Lount Jr., of Ohio State University. "Don't flake on the person you're having a first meeting with." Oh, and never show up late on a first date.