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Albany, NY – In today's Academic Minute, Dr. Philip Fernbach of Brown University reveals that when it comes to proving a point, weak evidence is often worse than no evidence at all.
Philip Fernbach is a postdoctoral research associate in the Department of Cognitive, Linguistic, and Psychological Sciences at Brown University. Fernbach's research uses behavioral studies and mathematical modeling to determine how people make decisions and judgments. His research on the Weak Evidence Effect was conducted in partnership with fellow Brown researchers Steve Sloman and Adam Darlow.
Dr. Philip Fernbach - Weak Evidence
One of the most important lessons from the study of mind is that our thinking is not like the rigorous syntactic operations of a computer. We are more like resourceful adventurers who can draw on a large store of knowledge and a few tricks to get by in whatever situation we find ourselves. This kind of thinking makes us very adaptable, but it also has a dark side, sometimes leading to mistaken patterns of thought.
Along with colleagues Steven Sloman and Adam Darlow I have been investigating an important kind of thinking: making predictions. We have found a peculiar pattern in people's predictions: When given weak but positive evidence for an outcome, people think the outcome is less likely than people given no evidence. For instance, people told about a newspaper endorsement of a single Republican candidate were less likely to gamble on the Republicans winning the mid-term elections than people not told about the endorsement. In another case, people told about a very short power outage actually thought a gallon of milk was less likely to be spoiled than people not told about the power outage.
Why does this happen? People make predictions by building a mental model of how the present will lead to the future. Like the resourceful traveler, we patch our models together from whatever evidence is most accessible. When given a weak piece of evidence, people are less likely to search for stronger evidence. So in the election example, focusing on the political endorsement made it less likely that people would think of other reasons the Republicans might win, like the poor economy or anger about the deficit. The paradoxical result was that a positive piece of evidence made people doubt the outcome.
So next time you find yourself thinking about the future in order to make a decision, stop and consider: "Am I taking everything into account that I should?"