single cause bias/ fallacy/ illusion

The single cause bias is a cognitive bias characterized by the tendency to think that there is one cause of a complex phenomenon. The single cause fallacy is the belief that there is a single cause for some complex phenomenon based on no evidence, and thus is a fallacy of assumption. The single cause illusion is the belief that there is a single cause for some complex phenomenon based on testimonials, biased scientific evidence, or communal reinforcement for the single cause. The illusion is based on confirmation bias and the fallacies of omitting relevant evidence, hasty conclusion, and false cause. The single cause bias is exemplified by the tendency to think that such complex phenomena as alcoholism, autism, cancer, mental illness, extreme weather conditions, or economic recessions are each due to a distinct single cause.

The single cause bias can be traced back to the earliest attempts to understand the world we live in. Whether there was too much rain or not enough rain, too much wind or not enough wind, a safe voyage or a disaster, it was always due to spirits or gods. The development of modern scientific methods of testing causal claims has eliminated belief in gods as the cause of natural phenomena, except for the hidebound religious fundamentalists who still look for a supernatural being as the cause of natural disasters or human evil actions. But science has not eliminated this bias in all those who recognize fundamentalism as primitive superstition. There are still people who believe there is a single source for mental illness, for example, and that they have the scientific evidence to prove it. Scientologists believe they have scientific evidence that all mental and physical illnesses are due to engrams. There are many psychotherapists today who think they have scientific evidence that all psychological problems are due to having been abused as children. Those who argue for single causes of such things as mental illness or cancer often follow the same methods. They make up stuff, as L. Ron Hubbard did regarding engrams and illnesses. They rely on anecdotes from personal experience as Freud and Bettleheim did. They ignore all evidence where the effect they are making claims about is found in the absence of the single cause they are trumpeting. They ignore all evidence where the single cause they are trumpeting occurs but the effect they link to it does not occur.

I can only speculate about the value of this bias. Cognitive ease might explain part of the virtue of the single cause bias. It's much easier to think about a single cause for a complex event than to think of several causes for the event; and it's much easier to look for a single cause of multiple similar events (alcoholics, cancer patients, etc.) than it is to look for multiple causes of the same type of event. Ignorance, superstition, and the intentionality bias played a role in the bias of our ancient ancestors who believed that a willful being like themselves was the cause of shipwrecks, floods, droughts, etc. Superstition and communal reinforcement still play a major role in this bias among religious fundamentalists.

As noted, it is not only superstitious religious fundamentalists who are affected by this bias. Many people today cite stress as the single cause of many physical and emotional problems. Many cite poor nutrition as the single cause of health issues and advocate supplements as the cure. Vaccines are being blamed for causing all kinds of neurological disorders. Many scientists and defenders of science search for the single set of personality traits that they believe will lead them to identify criminals, future mass murderers, believers in the paranormal, and conspiracy theorists. Some scientists jump from results in small studies on mice to grand conclusions about genes and complex human behaviors. The drive to search for a single cause seems to be based on little more than a bias. The finding of such single causes as child abuse, mental illness, neurochemical imbalance, easy access to guns, fantasy proneness, the presence of a gene or two in rodents or humans, anomie, and the like are illusions based on fallacies such as those mentioned above.

The harmful consequences of single cause illusions can be seen in the anti-vaccination movement and various quack cures for cancers, among other things.

See also the hidden persuaders (cognitive biases and illusions).

further reading

Carroll, Robert Todd. 2013. The Critical Thinker's Dictionary: Biases, Fallacies, and Illusions and what you can do about them.

Last updated 14-Jan-2014