Monday, November 26, 2012

magical thinking

 ...magical thinking is "a fundamental dimension of a child's thinking." --Zusne and Jones

Magical thinking is a belief in the interconnectedness of all things through forces and powers that transcend physical connections. Magical thinking invests special powers and forces in things and sees them as symbols on various levels. According to anthropologist Dr. Phillips Stevens Jr., "the vast majority of the world's peoples ... believe that there are real connections between the symbol and its referent, and that some real and potentially measurable power flows between them." He believes there is a neurobiological basis for this, though the specific content of any symbol is culturally determined. ("Magical Thinking in Complementary and Alternative Medicine," Skeptical Inquirer, 2001, November/December.)

Monday, November 19, 2012

causal fallacies

A causal fallacy involves making the claim that something (call it 'x') causes something else (call it 'y') when the evidence presented is insufficient to establish either that x is a necessary condition for y or that x is a sufficient condition for y. Causal fallacies usually involve either post hoc reasoning or jumping to a conclusion based on finding a correlation between x and y. The post hoc fallacy (that x causes y because x came before y) is discussed elsewhere. Here I'll focus on errors due to misapplied correlation.

Let's start with an example of some good causal reasoning. The claim that smoking causes lung cancer is based on data that demonstrate to a high degree of probability that had a person with lung cancer not smoked they would not have the kind of cancer they have today. We describe such a relationship as that of smoking to lung cancer as being of the type smoking is a necessary condition for lung cancer. Expressing it this way can be misleading though, so some explanation if required. Certainly, people who have never smoked can get lung cancer, so in that sense it is not necessary to smoke in order to get lung cancer. When we say that smoking is a necessary condition for lung cancer we mean that for the particular cancer a person has smoking was necessary. In simpler terms, this means that had the person not smoked they would not have gotten the kind of lung cancer that is caused by smoking.

Monday, November 12, 2012

negativity bias

  "The evil that men do lives after them; The good is oft interred with their bones." --Marc Antony, Julius Caesar by Shakespeare (act 3, scene ii)
"I hate losing more than I love winning." --Billy Beane:
Brief contact with a cockroach will usually render a delicious meal inedible. The inverse phenomenon—rendering a pile of cockroaches on a platter edible by contact with one’s favorite food—is unheard of." So begins a classic paper by Paul Rozin and Edward B. Royzman: "Negativity Bias, Negativity Dominance, and Contagion (2001).

You might think you're weird when a thousand good things happen but you focus on the one bad thing. You're not. That's the way our brains are hardwired. We're designed by nature to pay more attention and react more quickly and more strongly to negative than to positive news. One salient misdeed by a person will often outweigh years of good works. Years of building up a positive image can be destroyed in an instant by a single misstep. This tendency to give more weight to the negative is called negativity bias and is defined as "the propensity to attend to, learn from, and use negative information far more than positive information." Our brain evolved to react more quickly to fear than to hope, to respond to a threat more quickly and more intensely than to an opportunity for pleasure. And this trait has carried over into modern times in ways that are not always beneficial.

Monday, November 5, 2012

informal fallacies of reasoning

Logical fallacies are errors that occur in arguments. In logic, an argument is the giving of reasons (called premises) to support some claim (called the conclusion). Arguments may be classified as deductive or inductive. Deductive arguments assert or imply that the conclusion follows necessarily from the premises. Inductive arguments assert or imply that the conclusion follows with some degree of probability, not necessity. Deductive arguments are evaluated for validity. If the conclusion of a deductive argument follows necessarily from the premises, the argument is said to be valid. If the conclusion of a deductive argument does not follow with necessity from the premises, the argument is said to be invalid. Validity is determined by the form of the argument, not the truth or falsity of the premises or the conclusion. An argument with the  form If p then q; p; so, q is a valid argument, no matter what statements are represented by p and q. If p and if p then q are both true, then q must be true. An argument with the form If p then q; q; so p is invalid no matter what statements are represented by p and q. Even if q and if p then q are true, p is not necessarily true. (Note: to say a statement is not necessarily true is not the same as saying that it is false.) The invalid argument form just presented is called affirming the consequent and is known as a  formal fallacy. Inductive arguments may be evaluated by their form, but usually they are evaluated by other criteria. The fallacies of induction are called informal fallacies because they do not evaluate the form to determine validity. I'll go over the criteria for a cogent inductive argument as I discuss the informal fallacies below.