Via Andrew Garrett, this amusing image: two signs, one advertising a $50 reward for a lost ipod… and the other advertising a $51 reward for a lost ipod. Amusing, but I can’t see anyone actually calling the $51 guy.
Let’s assume you were indeed some kind of conniving scammer; how would you go about this, presuming that “take down the first poster” isn’t an option? The person who lists second needs to pick a value that increases the plausibility of their poster (is a round number) and provides an economic incentive to call them (is larger) without being self-defeating (is too expensive compared to just buying one).
If the poster had said $60, we might have taken it more seriously – it’s a round number, so it looks more independently plausible – but this doesn’t automatically make it more convincing than the first. When you’re approaching the two signs with the knowledge that one of them is a scam, you’re thinking more critically than usual, and so you’re trying to deduce which one is legitimate.
Seeing the two signs, you’re likely to run through something like the above chain of logic and conclude – one of these two is a scammer, and it makes sense that it’s the higher one. Would it, then, be smarter to deliberately flout the economic aspect and undercut the legitimate poster? Your price is the only way of signalling your plausibility you have, and a lower price implies that you were first to advertise – because it’s irrational to make a lower bid after a higher one.
There is a counterargument that most finders wouldn’t be this honest – they would be motivated by nice simple economic motives first, and so would call the person offering an extra $10. But this doesn’t really reflect the situation: we know that the market value of a second-hand ipod must be more than the amount the scammer offers as a reward, and so a large number of those motivated by purely economic motives would no doubt want to sell the ipod (or keep it). If someone is already contemplating the reward posters at all, they’ve indicated a willingness to take a nominal loss in the interests of “justice” by returning it to its owner.
Alternatively, I suppose, you could counterbid $50, thus anulling pretty much any benefit either you or the original poster would have and turning it into a game of chance. Which offers better odds?
I wonder what we’d get from testing this… is there a sweet spot, just above or just below the original reward, where you’re most likely to get a response?