In his article, Knobe discusses the role of moral judgments in people's understanding. The author focuses his study on the moral influence present in the process of cognition. In discussing the motivational bias hypothesis (sect. 4.1), Knobe mentions studies in patients who had a lesion in the ventromedial prefrontal cortex. These studies tried to demonstrate the non-involvement of affective reaction in the process of moral judgment.

In this commentary, we consider moral judgment in depressed subjects. We feel that depressive mood is particularly relevant to the negative moral judgments often made by patients with depression. In the psychopathology of depression, patients' actions and thoughts can be affected by the depressive mood, which in turn tends to affect their moral judgments. This psychopathological process is characterized by ruminations of negative thoughts. Patients with major depression understand the world and themselves in the same way, that is, in a negative way. Here, these disturbed thoughts can be understood as a distortion of moral judgments influenced by the presence of depressive mood. In the moral judgments, patients often evaluate themselves or their acts as something “bad” or “wrong.” This process supposes that patients are evaluating themselves axiologically. During this process, depressed patients consider themselves to “blame.” Such depressed patients with these negative moral judgments and thoughts can be an example for the line of study developed by Knobe. Patients' negative moral judgment and other psychopathological alterations return to normal with the remission of depression (Benedetti et al. Reference Benedetti, Bernasconi, Blasi, Cadioli, Colombo, Falini, Lorenzi, Radaelli, Scotti and Smeraldi2007). This process of continuous and rigid negative moral judgments may have a biological explanation.

What kind of process can be underlying this alteration on negative moral judgment in depression? In normal human subjects, studies with functional brain imaging have found increased activity in brain areas in a resting state and reduced activity when there is a proposed goal for brain function . This organized mode of brain function identified in specific brain regions constitutes the default system (Drevets et al. Reference Drevets, Price and Furey2008). A disturbance in this network can explain depression symptomatology. Studies developed by Sheline et al. (Reference Sheline, Barch, Price, Rundle, Vaishnavi, Snyder, Mintun, Wang, Coalson and Raichle2009) found that depressed subjects showed less decrease in activity than control subjects in areas of the default system, or default mode network (DMN), during performance of emotional tasks. These findings have supported the view that alterations in areas of the DMN may constitute a basis for the disordered self-referential thoughts of depression.

In Knobe's article, there is a mention about a study investigating cognition in people who don't have immediate affective reactions as a result of lesions in the ventromedial prefrontal cortex. He uses this study to show that the results of his analyses about moral judgment in normal subjects are not due to an affective reaction. However, in people with distortion of judgment caused by depressive mood, the neural dysfunction in specific brain areas found in depression investigations can explain the moral judgment disturbance, and supports the interference of the depressive mood on moral judgments.

This construction supports our view that the neural basis of depression may explain depressive mood and, consequently, moral judgment; albeit it does not exclude Knobe's point that moral judgment may occur independently of affective reaction.