The explanation of this I'd go to first is a system 1 / system 2 explanation (e.g. your intuitive system [system 1] picks the tastier thing, and overriding that requires activity from deliberative decision-making (system 2) that can be tied up with cognitive load), so I'd recommend looking in Thinking Fast and Slow, which I think mentions at least one Kahneman and Tversky experiment on a similar subject.