"... can an information-processing system that runs on gradients of lifelong bliss really sustain critical insight? In principle, at least, yes. The functional analogues of depressive realism can be sustained without the nasty textures of low mood. One snappy formulation sometimes used to define "information" is "a difference that makes a difference". On this basis, what's important in the context of the information-theoretic paradigm is not our absolute position on the pleasure-pain axis, but our differential sensitivity to emotionally-tagged variations in fitness-relevant stimuli."