[Link] Sparrows may be vulnerable to sunk-cost-like effects

You walk into a store that sells two identical candies. Would you buy the candy that ordinarily costs $2 at 50% off (for one dollar), or the candy that ordinarily costs 10$ for 80% off (for one dollar)?

In an isomorphic situation, sparrows preferred the latter deal.

http://​​users.ox.ac.uk/​​~kgroup/​​publications/​​pdf/​​kacelnik_marsh_2002_animbehav_costs.pdf