Multiple-food-unit-incentive effect: Nonconservation of weight of food reward by rats.

Abstract

A common assumption is that the incentive value of food is determined by weight independently of number of food units. In Experiments 1 and 2, rats trained in a T-maze with four 75-mg pellets in one alternative and a single 300-mg pellet in the other alternative developed a preference for the 75-pellet alternative, which did not diminish with extensive training. When the locations of the 75-mg and 300-mg pellets were reversed, rats reversed their choice of arm. Rats preferred a 300-mg pellet to four 45-mg pellets (Experiment 2) and four 75-mg pellets to four 45-mg pellets (Experiment 3). Thus, rats prefer multiple-to single-food units; this effect is permanent rather than temporary, and the incentive value of food is not determined by weight of food alone or number of food units alone. Rats may count food units, judging a given weight of food as greater the greater the number of units-a failure of conservation common, possibly, to a number of species from birds to humans.

The “Euro Illusion”: Illusion or Fact?

“…For instance, in a study of operant conditioning in chickens, a kernel of corn divided into four pieces was found to be a more effective reinforcer than the whole kernel. Similar results have been demonstrated in studies of rats; for instance, it has been found that rats preferred four small food pellets as opposed to one large food pellet (Capaldi et al 1989). In studies of people, self-esteem was enhanced when a single statement, containing positive attributes (e.g., I am creative, analytical, and verbal) about oneself was divided into distinct statements (e.g., I am creative; I am analytical; I am verbal) (Showers 1992).…”

A Method for Testing Food Preference in Animal Experiments

“…Investigators use the two bottle test [10,16], which includes a working chamber fi tted with food reservoirs located outside the chamber, and tubes in the working sector allowing the animals to access test liquid foods with different taste properties or different concentrations of test food substances (saccharine, fructose, etc.). This apparatus provides for study of food preference based on taste reception of different samples of edible food and/or its calorifi c value, but it does not provide for studies of the role of the primary (sensory) reinforcement associated with the remote actions of natural food stimuli (food type, quantity, size, color) which are used by subjects to assess the attractant properties of the test foods and make the choice before taking and eating.Another method for studying food preference in rodents by presenting the animals with various food samples in solid form is also known [8,15]. In these experiments, selection of the preferred food (food granules and tablets of different sizes and weights) is performed manually by the animals by combined use of the tactile, muscular, and taste analyzers.…”

“…Another method for studying food preference in rodents by presenting the animals with various food samples in solid form is also known [8,15]. In these experiments, selection of the preferred food (food granules and tablets of different sizes and weights) is performed manually by the animals by combined use of the tactile, muscular, and taste analyzers.…”

“…The formation of food preference is known to be tightly connected with the level of motivation, which depends on the status of the blood and the calorifi c value of food entering the stomach [9,12,17], and its taste properties, which are mediated via orosensory stimulation when food enters the mouth, as well as from stimulation signaling the physical properties, time of ingestion, and quantity of food received [1,2,6,7,8,15].…”

“…

The formation of food preference is known to be tightly connected with the level of motivation, which depends on the status of the blood and the calorifi c value of food entering the stomach [9,12,17], and its taste properties, which are mediated via orosensory stimulation when food enters the mouth, as well as from stimulation signaling the physical properties, time of ingestion, and quantity of food received [1,2,6,7,8,15].Studies of food preference and its associated level of food motivation in experiments in different animal species generally involve presenting subjects with a situation in which they can make alternative choices of feeders and foods with different taste properties. Investigators use the two bottle test [10,16], which includes a working chamber fi tted with food reservoirs located outside the chamber, and tubes in the working sector allowing the animals to access test liquid foods with different taste properties or different concentrations of test food substances (saccharine, fructose, etc.).

…”