Archive for the ‘Biases & Heuristics’ category

People think “natural” meds have less side-effects…

March 5, 2011

… but are equally effective at combating disease.


Unit bias

January 28, 2011

One of the most obvious cognitive bias’ that  has application to the understanding and treatment of obesity is the unit bias. Unit bias is a “sense that a single entity (within a reasonablerange of sizes) is the appropriate amount to engage, consume, or consider.” In regards to food, people will think that a  “unit” like a single package, tablespoon, plate, bowl, ect is the right amount of something to eat. If you click the above link you can read more about the unit bias.

Today, the good folks at Obesity Panacea posted some new info on the unit bias. They discuss a new study in Obesity that looked at the effect of 100-calorie snack packs on voluntary consumption between overweight and normal weight individuals.

If there is a unit bias, then 100-calorie snacks packs (which have come under much fire) should lead people to eat less. If so, then maybe they aren’t as silly as everyone has said. So, what did researchers do and what did they find?

A total of 42 undergraduate students participated in the simple study which basically had the participants snack on crackers while watching a sitcom…

Half of the participants were given one large 400-calorie package of crackers or a similar-sized package that had then been sub-divided into four smaller 100-calorie sub-packaged crackers. They were blinded to the purpose of the study.

After watching the show, the crackers not consumed by the participants were counted to calculate everyone’s caloric intake. Also, each participant was asked how many crackers they think they consumed.

Turns out, overweight participants ate significantly more crackers when eating from one large package than from four small packages. In fact, they consumed more than double the number of calories with the bigger package: 384 calories versus 176 calories.

Surprisingly, there was no difference in consumption between package conditions among the normal-weight participants.

Interestingly, the researchers found that only the overweight subjects were susceptible to unit bias! This is a really cool finding and it offers us a new contribution to overweight & obesity.

Research I’d like to see next is whether or not eduction of proper portion sizes can help overcome unit bias. Another possibility is that changing your environment so that your home is stocked with smaller bowls or plates could lead to a spontaneous reduction in calorie intake.

Affect Heuristic

June 2, 2010

NOTE: This is the first post in a series that will detail various biases & heuristics and how they affect truth seeking in health/fitness.


When making decisions about the costs and benefits of something, people often utilize “heuristics,” which are rules of thumb that guide us towards making quick decisions. Heuristics can be beneficial or detrimental to good decision making depending on the context.

“Affect” is a quick good or bad feeling that one gets in a situation, hearing/reading a word, looking at a picture, ect.

The affect heuristic causes us to use our perception of one positive or negative aspect of something and use that to judge other aspects of that thing as being similarly positive or negative even if such a judgement may not be warranted. So, the affect heuristic is what happens when we get a good or bad feeling (fear, pride, ect.) and let that emotion influence our decisions and beliefs.


In this post I only want to look at how the affect heuristic can cause us to misjudge the truth about things in heath/fitness.

One of the easiest ways to understand this is to think about the connotations that  certain food words have for most people.

Good Feelings




Bad Feelings



The first group of words give many people a positive affect, that is, positive feelings. The other, negative affect. For whatever reason, things just seem more healthy at first glance if they are “organic,” or “all-natural.”

Watch the following video of how a waiter uses positive affect to skew the perceptions of dinners. Everything from the setting (fancy restaurant) to the words he choses to use (e.g. fancy French words) are examples of using positive affect to make someone like something more than evidence warrants. Warning: bad language.


It should come as no surprise that your favorite food manufactures are well aware of this fact and use it to influence consumer perception of their products. Put “organic” on a package and the positive connotation with this word causes the masses to flock to it pesticide free goodness. It doesn’t matter if people have actually looked at the evidence to see whether or not spending the extra money on organic food is worth it, it just “seems” like organic should be better because the notion feels healthier.

My purpose with this post isn’t to take a side in the organic vs. conventional debate, just to bring awareness of the affect heuristic to those who do believe it is better. Try your very best to be honest. Is the connotation that words like organic, wholesome, natural, and artificial have skewing my perception of the evidence?

Anyways, there are many more ways that the affect heuristic takes form in the fitness industry. See if you can brainstorm some and post them in the comments!

Additional Resources

(1) Rational actors or rational fools?

(2) Affect bias @ skeptics dictionary

(3) Organic food is NOT more nutritious

(4) Organic IS better for you