UCLA

The Conjunction Fallacy in people

In 1983, Tversky and Kahneman reported the now famous Linda Problem as an example of a logical fallacy in which the conjunction of two independent events or traits were judged by human participants to be more likely than either alone. This logical fallacy has been heavily studied in humans over the past 40 years. We recently reported a series of experiments showing a similar type of fallacy in rats using a trial-wise contingency learning procedure. This fallacy is surprisingly robust to manipulations of trial-type base rates. This has led me to propose a foundational principle of perception/cognition called the Positivity Bias which plays a role in perception, learning, and decision making. The Feature Positive/Feature Negative effect (FP/FN) in visual pop out is an example in the perceptual domain. FP/FN effects are also found in learning paradigms. I believe the conjunction fallacy is another example of this bias acting at the time of decision making.

Is memory of eating better than memory for non-eating episodes?

A series of studies with former graduate student Benjamin Seitz tackled this question. We had participants come in to the lab and engage in the following task. They watched a short TED talk video on the computer while listening to “beeps” on head phones. They were instructed to take an action each time they heard a beep. The three conditions were: 1) move a plastic bead into a glass jar; 2) move an M&M into a glass jar; or 3) eat an M&M. After the video was finished, we asked participants to estimate how many actions they had taken (e.g., how many beads or M&Ms had they moved, or how many M&Ms had they eaten). Participants estimations of eating M&Ms was more accurate to the actual amount (30) than were estimations of moving M&Ms or beads. This simple task revealed that eating events leave more accurate (better stored, more easily retrieved?) memories.