Compared to other brain functions (like remembering and deciding), how the brain reflects mood is much less well understood. One reason is that there is no objective right answer to the question, "How happy are you?" Consequently, mood cannot be studied by benchmarking against percent correct on behavioral tasks. While challenging, we cannot shy away from understanding mood given that ~20\% of adults will experience a mood disorder at some point, and for ~30\%, existing treatments will be ineffective. Here, we build on work that modulates, probes, and models fluctuations in subjective happiness as individuals experience wins and losses in a gambling task. A pooled mood model fit to behavioral data from eight human subjects provided reasonable predictions of happiness fluctuations for each subject's held-out data (0.43