To me, this is explained by the idea that we will be competing, not cooperating, with the ultimate winner.
If I am observing the contest and not participating, I would want the weaker party to win so that the remaining population dominates me less. If David gets lucky and beats Goliath, I only have to compete with David in future contests - if Goliath wins, I may have to go up against him next time.
Intuitively, this seems to explain the tendency quite well - a political victory by, let's say, Canada over the US, feels like it would "take them down a peg" and reduce the power imbalance between the UK (where I am) and the US. Equally a defeat of Roger Federer by a low-ranked player reduces my feelings of inferiority compared to the "superhuman" Federer.
Of course this would be quite different if I were entering a doubles contest - I'd much rather be Federer's partner - or choosing sides in the US-Canadian war. I don't think the underdog effect survives if I'm actually involved in the fight.
To me, this is explained by the idea that we will be competing, not cooperating, with the ultimate winner.
If I am observing the contest and not participating, I would want the weaker party to win so that the remaining population dominates me less. If David gets lucky and beats Goliath, I only have to compete with David in future contests - if Goliath wins, I may have to go up against him next time.
Intuitively, this seems to explain the tendency quite well - a political victory by, let's say, Canada over the US, feels like it would "take them down a peg" and reduce the power imbalance between the UK (where I am) and the US. Equally a defeat of Roger Federer by a low-ranked player reduces my feelings of inferiority compared to the "superhuman" Federer.
Of course this would be quite different if I were entering a doubles contest - I'd much rather be Federer's partner - or choosing sides in the US-Canadian war. I don't think the underdog effect survives if I'm actually involved in the fight.