Numerosity Can Ruin Your Diet

The numerosity heuristic can ruin your diet.

According to numerosity, people pay more attention to the number of units rather than the type of units which leads to faulty conclusions. Research shows we will pay more for a 7-day vacation than a one week vacation, and will complain less about a flight that is delayed for 1 hour than for 60 minutes.

It turns out this bias is already being exploited in ways I hadn’t imagined. Researchers at the W. P. Carey School of Business looked at the relationship between “restrained eaters” (aka chronic dieters) and small packages of snacks. Their observations are startling:

• “Mini-packs” are viewed as diet food, even though they contain largely unhealthy items (partially due to marketing, I believe).
• Consumers believe multiple mini-packs contain more calories than the equivalent number of snacks in a single larger package (the numerosity effect).
• The contradiction between a diet food and lot of calories causes stress in restrained eaters which encourages them to eat more (mini-packs are bad for diets).

There’s some evidence companies are intentionally promoting products which exploit consumers’ weaknesses and psychological discomfort. And, if they are, it’s probably very lucrative. Mini-packs usually cost more than twice as much per ounce as the equivalent normal size.

Regardless, beware of the numerosity effect. Numerosity can ruin your diet and cause you to buy things you don’t need.