Philosophy 210:
Practice With Confirmation Bias, The Availability Error and the Representativeness Heuristic


INSTRUCTIONS: Which of confirmation bias, the availability error and the representativeness heuristic best describes each passage? Pick only one. Answers are at the bottom of the page.

1. General Ulysses S. Grant's assessment in the Battle of Shiloh in 1862 was that the Confederate forces under General Pierre Beauregard were preparing defenses and were "heartily tired". Despite information from frontline units, and one colonel who reported "thousands of rebels out there in the woods," General Grant refused to alter his initial hypothesis about the enemy. When he continued to receive reports about enemy movements, his assessment was that it was, at most, a small attack against an isolated division, but clearly not a large-scale offensive. The next morning, as Grant was eating breakfast, thousands of Confederates began their attack. What best describes Grant's mistake?

2. Those who advertise lotteries do not want the first thing that comes to a potential ticket-buyer's mind the thought that he has a one-in-40-million chance of winning. Instead, they put forth recent winners in the hope that what will come to mind when the chance to buy a ticket arrives is the happy winner. Thus, people tend to think that it is more likely than it is that they will win. What best describes their error in thinking?

3. What is the probability that person A (Steve, a very shy and withdrawn man) belongs to group B (head librarians) or C (exotic dancers)? Most people will say that he is more likely to be a head librarian. Why?

4. In its 1996 Spring/Summer issue (pp. 217-252), the postmodern journal Social Text published an article by Allan Sokal, Professor of Physics at New York University, entitled "Transgressing the Boundaries: Towards a Transformative Hermeneutics of Quantum Gravity." The article was a hoax submitted, according to Sokal, to see "would a leading journal of cultural studies publish an article liberally salted with nonsense if (a) it sounded good and (b) it flattered the editors' ideological preconceptions?" It would. Needless to say, the editors of Social Text were not pleased. [Sokal says] I intentionally wrote the article so that any competent physicist or mathematician (or undergraduate physics or math major) would realize that it is a spoof. Sokal wanted to criticize the "epistemic relativism" and "social constructivism" of the New Left in a New Left journal but felt the only way they would let him do so would be if he pretended to share their ideology. What best describes the thinking attributed to the editors of Social Text?

5. If Joanna is dramatic and histrionic, stereotypical qualities for actresses, people typically think that she is more likely to be an actress than a waitress. In fact, given the number of waitresses vs. the number of actresses, she is much more likely to be a waitress. What best describes this error in thinking?

6. If surrounded by slot machines people are more likely to continue feeding money into their machine, because they will occasionally see someone else win and think their chances are high of winning: they remember others winning much more readily than they remember all the times they and others have lost. What best describes their error in thinking?

7. During the Civil War Battle of Chancellorsville in May 1863, General Oliver O. Howard, Commander of the Union Army's 11th Corps, received a number of initial reports early on 2 May, suggesting that the Confederate forces opposite his position were a covering force for a Confederate retreat. These initial reports included a report from General Joseph Hooker, Howard's superior, who stated that the Confederate forces were clearly in retreat. As the day progressed, however, General Howard received a variety of eyewitness reports that indicated the Confederate forces were instead massing for an attack. Although he was aware of eyewitness information, he apparently placed more emphasis on the earlier reports. At 5:15 p.m. on 2 May, Confederate troops stormed through the completely surprised 11th Corps, turned the Union flank, and eventually won this battle. What best describes Howard's mistake?

8. Suppose that someone is asked to estimate the proportion of words that begin with the letter "R" or "K" versus those words that have the letter "R" or "K" in the third position. Most English-speaking people could immediately think of many words that begin with the letters "R" (roar, rusty, ribald) or "K" (kangaroo, kitchen, kale), but it would take a more concentrated effort to think of any words where "R" or "K" is the third letter (street, care, borrow, acknowledge); the immediate answer would probably be that words that begin with "R" or "K" are more common. The reality is that words that have the letter "R" or "K" in the third position are more common. In fact, there are three times as many words that have the letter "K" in the third position. What best describes this error in thinking?

9. I recently heard that llamas don't get tongue infections. So if I eat a lot of llama tongues, I shouldn't get any tongue infections either! What best describes my error?


1. confirmation bias
2. the availability error
3. the representativeness heuristic
4. confirmation bias
5. the representativeness heuristic
6. the availability error
7. confirmation bias
8. the availability error
9. the representativeness heuristic