Monday, June 11, 2012

The power of generic statements

During the last election, we heard lots of generic statements about political parties.  Ads told us that Democrats want to allow the government to intrude on the rights of individuals.  We heard that Republicans want to take away funding for key social services.  We were told that the Tea Party was racist.

These kinds of statements are called generics.  A generic statement is one that makes a blanket statement about the members of a category.  We use these kinds of sentences all the time, even when we are not trying to be persuasive.  For example, the simple sentence “Cardinals are red” is a generic.  We often use sentences like this when teaching people about the properties of objects.

It turns out, though, that the psychology of generic statements is quite interesting, and that it has important implications for how we use them to persuade people.  The psychology of these generics was explored in a paper in the November, 2010 issue of Cognitive Science by Andrei Cimpian, Amanda Brandone, and Susan Gelman. 

They explored two facets of generics.  The first is the number of members of a category that have to have a property in order for us to be willing to use the generic statement.  For example, most of us would be willing to say that cardinals are red, even though only about half of cardinals (the males) are actually red.  Female cardinals are a dull color that helps them hide from predators.  The second facet is our belief about what proportion of category members people believe have a property when they hear a generic statement.

These researchers had people do one of two tasks.  In one condition, they described novel animals that live on a fictitious island.  People were told about a property that the animal has.  Some of the animals had particularly distinctive or dangerous properties, while others had properties that did not distinguish them from other animals.   They were also told what percentage of the animals of that type had the property.  These percentages varied from 10% to 100%. 

 One group was asked whether a generic statement (like “Morseths have silver  fur”) was appropriate to describe the animals.  People asked this question felt that generic statements were most appropriate to use when the property was distinctive.  That is, people feel that generic sentences are less appropriate for describing properties of objects that are common to lots of different things than for those properties that are distinctive.  Of particular interest, though, people were often willing to accept the generic statement even if only 50% of the animals had the property. 

A second group was asked to predict how many members of a category were likely to have a property given a generic statement.  If people heard a statement like “Morseths have silver fur” they believed that about 90% of them actually had the property. 

Think about this.  It means that people are willing to use generic sentences to describe a category when only 50% of the category members have that property.  But, when people hear a sentence with a generic in it, they assume that almost all of the category members have that property.

These results really matter.  They mean that when we hear an ad with a generic statement in it, we assume that it applies to almost all of the members of the category being described.  Hearing an ad that mentions Democrats, Republicans, or the Tea Party can be misleadingly persuasive by making people believe that almost all of them have a common set of beliefs.    

What can you do about this?  When you hear an ad that uses generic statements, think about how many members of a category you really think it applies to.  It will take a little work on your part, but it can ultimately help you to make better decisions.