Academic journal article Psychonomic Bulletin & Review

Less Means More for Pigeons but Not Always

Academic journal article Psychonomic Bulletin & Review

Less Means More for Pigeons but Not Always

Article excerpt

Published online: 1 April 2014

© Psychonomic Society, Inc. 2014

Abstract When humans are asked to judge the value of a set of objects of excellent quality, they often give this set higher value than those same objects with the addition of some of lesser quality. This is an example of the affect heuristic, often referred to as the less-is-more effect. Monkeys and dogs, too, have shown this suboptimal effect. But in the present experiments, normally hungry pigeons chose optimally: a preferred food plus a less-preferred food over a more-preferred food alone. In Experiment 2, however, pigeons on a less-restricted diet showed the suboptimal less-is-more effect. Choice on control trials indicated that the effect did not result from the novelty of two food items versus one. The effect in the less-food-restricted pigeons appears to result from the devaluation of the combination of the food items by the presence of the less-preferred food item. The reversal of the effect under greater food restriction may occur because, as motivation increases, the value of the less-preferred food increases faster than the value of the more-preferred food, thus decreasing the difference in value between the two foods.

Keywords Affective heuristic · Less-is-more effect · Suboptimal choice · Paradoxical choice · Level of motivation · Pigeons

Although we think of ourselves as rational beings, we do not always make optimal choices. For example, people will often give greater value to an overfilled 5-oz container with 7 oz of ice cream than to an underfilled 10-oz container with 8 oz of ice cream (Hsee, 1998). In such a case, one attribute, the amount of ice cream relative to the size of the container, is evaluated, while another, more important attribute-the actual amount of ice cream-is neglected. This phenomenon is known as the less-is-more effect (Slovic, Finucane, Peters, & MacGregor, 2002).

The less-is-more effect is well documented in humans. In one study, subjects were asked to rate a set of 24 pieces of dinnerware, as well as another set of the same 24 pieces plus 16 more pieces that included nine broken pieces (Hsee, 1998). Objectively, the 40-piece set was more valuable than the 24- piece set-since even if the nine broken pieces were discarded, 31 intact pieces of dinnerware would remain-but despite this, subjects still rated the 24-piece set more highly. Similarly, at a sports-card show, a set of ten baseball cards in mint condition was auctioned, as well as the same ten cards with an additional three cards that were judged to be in poorer condition (List, 2002). Although the three cards in poorer condition were not worth as much as the cards in mint condition, they were each worth something. Nevertheless, the highest bid was 59% higher on average for the 10-card set than for the 13-card set.

In another study (Chernev, 2011), subjects were asked to judge the number of calories in either a hamburger alone or a hamburger together with three celery sticks. On average, the hamburger alone was judged to have 734 calories, whereas the hamburger together with three celery sticks was judged to have only 619 calories. Thus, although the presence of the relatively healthy celery sticks actually added to the total calories, it was judged to reduce the calorie value of the hamburger.

The less-is-more effect is a specific case of the more general affect heuristic, in which qualitative aspects of a set are attended to more than the quantitative aspects. According to Hsee (1996), the affect heuristic will normally be applied to attributes that are readily evaluable, such as item quality, rather than by those that may be objectively more important, such as the total objective worth of a set of items of mixed quality. One can think of the lesser-valued items in the set as having a devaluing effect on the greater-valued items.

Interestingly, animals, too, appear to experience this kind of suboptimal judgment. For instance, monkeys that willingly ate a piece of sliced vegetable or a grape showed a preference for a grape over the vegetable slice when offered a choice between them. …

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