It would be helpful if we had precognitions about murderers. We could take a person like Wu Huanming, the latest suicide/murderer to strike a Chinese school, and put him away forever before he could do any damage. Of course, we don't have that ability to read persons' intentions, though science may be bringing us down that path.
If we had been able to peer into Wu's brain minutes before his violent acts, what would we have found out? Well, most importantly, we would have learned about his intent and, seeing his preparations, certainly acted to stop him.
Reading Wu's brain tape, we would likely have seen a plan that copied other persons who had made attacks at schools; certainly the knowledge that those attacks had occurred would have been stored. In the emotional area of Wu's brain, we would almost certainly find a willingness or desire to die.
In reviewing Wu's brain tape we would learn why he did what he did. Perhaps,as reported, one factor was a property dispute with the owner of the school. What we wouldn't learn, however, is anything about why Zhang Minsheng killed school children in March in Fujian Province or why Yang Jiaqin murdered a second-grader and an elderly woman in Guangxi last month.
In other words, while our tape of Wu would tell us about him, it wouldn't allow us to generalize about other similar murderers, nor to understand the many thousands more people who may have similar tapes to Wu but don't commit the same heinous acts. But even without their tapes, understanding Wu and others like him is what we try and do, believing that we somehow then can prevent those acts in the future.
Commentators wrap these ad hoc explanations into convenient and untestable theories that suggest that we should have known all along that the societal factors would and will continue to produce these types of aberrant individuals. The explanations are quite convenient and facile because when someone who is unemployed attacks and wounds 29 school children in Jiangsu Province, as happened in April, his apparent economic disaffection can be neatly dovetailed with Wu's, who was apparently well-off by his village's standards.
That is, Wu must have secretly harbored disaffections and resentments against society, despite comfortable economic circumstances, perhaps because society had not dealt him enough challenges to deal with whatever inner demons he harbored. Ad hoc explanations neatly accommodate apparent contradictions.
Employing hindsight bias, pundits can take whatever facts fit into their preconceived notions and work backwards. They start with the outcome and suggest a logical nexus to the genesis. But like a math problem to which we know the answer is 3 for example, there may be an infinite number of question possibilities, 6-3 or 2+1, etc. What's more, there is no way to scientifically challenge the explanation.
That is not to suggest that psychology is useless in helping us to understand society's problems. Psychologists can test, observe, predict, describe, and offer suggestions to change, human behaviors. Controlled experiments can be arranged to understand how people are likely to react given certain circumstances. Psychologists can study correlations to learn how various factors are likely to change with regard to other factors.
What psychology and pundits should avoid is offering overarching explanations after the fact that purport to explain behaviors according to grand theories and then suggest future prescriptions based on those theories. For that, we will need to rely on "Minority Report."