Fig. 1

Two individuals in a relatively good work environment. Time on the X axis is in weeks, whereas mood is a function of the running weighted average of surprise (e.g., average negative surprise relates to low mood). A depressed agent (blue line) learns much more from positive surprises than negative surprises and, as a consequence, is set up for chronic disappointment. This fosters persistent low mood and can be thought of as an instantiation of “mood-reactive depression” [24]