There is new research on deficits in reward processing as a possible endophenotype for depression. A probabilistic reward learning task (PRT) has the most relevant data. Using signal-detection procedures, participants are shown one of two stimuli and instructed to hit a corresponding key. The two stimuli represent different values (one with more value than the other to produce a response bias). Compared with control groups, depressed individuals tend to fail to create a response bias, therefore valuing both stimuli as the same. There is also preliminary evidence that response bias on the PRT shares genes with depression.