Further evidence of a connection between brain physiology and psychological states has recently been uncovered in the form of a correlation between electrencephalograph patterns and characteristic moods. A study showed that participants who suffered from clinical depression exhibited less left frontal lobe activity than right, while, conversely, characteristically good-natured participants exhibited greater left lobe activity. Thus one's general disposition is a result of the activity of one's frontal lobe.
Each of the following, if true, weakens the argument, EXCEPT:
(a) Many drugs prescribed to combat clinical depression act by causing increased left lobe activity.
(b) Excessive sleep, a typical consequence of clinical depression, is known to suppress left lobe activity.
(c) Frontal lobe activity is not subject to variation the way general disposition is.
(d) Earlier studies indicated that frontal lobe activity and emotive states are both caused by activity in the brain's limbic system.
(e) Social interaction of the kind not engaged in by most clinically depressed people is known to stimulate left lobe activity.