Silly Humans Can’t Count: The 29% Effect

From a new study in the Journal of Consumer Research, how humans can’t count:

Consumers often have a distorted view when they compare information that involves numbers, according to a new study in the Journal of Consumer Research.  “As a consumer, would your preference for a dishwasher depend on whether its warranty level is expressed in months rather than years?” write authors Mario Pandelaere (Ghent  University, Belgium), Barbara Briers (Tilburg University, the Netherlands), and Christophe Lembregts (Ghent University, Belgium).

To most consumers, the answer is “yes.” The difference between an 84-month and a 108-month warranty looks bigger than the difference between a seven-year and a nine-year warranty, despite the fact that both differences are exactly the same.

“Qualitative information can usually be specified in alternative units,” the authors write. “In many cases, however, the specific unit in which information is described is arbitrary. For instance, product quality ratings may be expressed on a scale from 0 to 10 or on a scale from 0 to 100,” the authors write. “People typically fail to realize that the unit of quantitative information is arbitrary. They just focus on the number of scale units used to express a certain difference.”

As a result, higher numbers seem to represent bigger quantities. This “unit effect” is the reason why consumers perceive a bigger difference between ratings 90 and 95 out of 100 than they do between a 9 or 9.5 out of 10.

Source:

How to Make a 29% Increase Look Bigger: The Unit Effect in Option Comparisons. Mario Pandelaere, Barbara Briers and Christophe Lembregts. The Journal of Consumer Research, August 2011 [-]

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