[nis0s]

Maybe someone who has read the paper can confirm, but I think correlating optimism with a longer reward period is only meaningful if there is a comparative analysis which looks at what level of optimism presents in rats which wait longer for a reward and do not get it. Moreover, what level of optimism presents in rats which have a mixed reward system, i.e., sometimes getting a reward for waiting longer and sometimes not getting it.

I find that cognitive scientists often neglect these basic permutations, and present more intuitive results which are easier to accept because of any number of human biases, but may ultimately be an incomplete presentation of reality. I suspect that optimism traits and reward wait period are uncorrelated, and optimism in rats at least depends on some neurochemical factor.