Previous studies showed that rats preferred and also ran faster for multiple pellets than a single pellet of food. Here, we manipulated the rewarding effects of surface area occupied by food pellets on preference and running speed of rats trained on a T-maze. Twenty-two male adult Sprague-Dawley rats were trained to prefer one T-maze arm containing 30 food pellets scattered and the other arm with 30 pellets clustered. There was a significant preference for clustered food pieces over the scattered ones. The choice of the clustered food pieces may be explained by the optimal foraging theory to maximize energy gain. Therefore, larger surface area occupied by food pieces may be less rewarding when unnecessary energy is expended.

Increasing vegetable consumption among the adult population is a major goal, as the health benefits of vegetables can decrease one's risk of heart disease, cancer, diabetes, and obesity. The current study examined a potential strategy to increase consumption of vegetables by pairing them with a dip and a TV distraction. Based upon results of previous, similar research studies (Blass et al., 2006; Fisher et al., 2012; Johnston et al., 2012; Mittal, Stevenson, Oaten, & Miller, 2011), we hypothesized that eating vegetables with dip or while distracted with a television sitcom would result in increased consumption. We also hypothesized that both dip and a distraction together will synergistically increase vegetable consumption. A total of 126 college students were assigned to one of four conditions: eating vegetables with dip, with dip and a television distractor, with only a television distractor, or without either dip or a television distractor. While television had no significant influence on vegetable consumption, pairing vegetables with a dip significantly increased consumption of vegetables. Pairing vegetables with a dip may prove to be an effective strategy for increasing vegetable intake in the adult population.

Statistics are rising for adults who are overweight and/or obese, putting them at higher risk of developing serious health problems. Eating fewer portions of vegetable than the daily-recommended amounts contributes to this increase with. College students, being more susceptible to weight gain as they are transitioning from childhood to adulthood. Previous studies demonstrated that children ate more vegetables when repeatedly paired with a low-fat dip compared to when served plain. The current study examined whether this effect was also successful in college-aged subjects. A total of 148 (55 males, 91 females) college-aged students from an introductory psychology class at Arizona State University (Tempe, AZ) participated in the study. Subjects were randomly assigned to receive cauliflower or broccoli (raw) either served plain or with low-fat ranch dressing. Subjects showed a greater preference for and consumption of the vegetable plain that was previously given with dip than without dip. These findings suggest that serving vegetables with low-fat ranch dip two times can increase the liking and consumption of vegetables in college students.

Previously we found that subjects ate less from a four-piece bagel than from the same bagel served whole. Here, we determined if subjects differed in their perception of the amount of food based on the number of pieces of food served and measured the effects of these judgments on the amount of food consumed. A total of 213 (140 male, 73 female) undergraduate students with a mean age of 19 years participated in this study. Subjects were shown a whole food and the same food cut into pieces and asked which they perceived to be larger either before or after consuming that food, or not asked at all. We found that subjects ate less from a whole bagel than from a four-piece bagel. Furthermore, significantly more subjects perceived the whole bagel to be more food when asked this question after consumption of the bagel than before. People may be more familiar with the amount of satiation expected from a whole bagel than the four-piece bagel and this perceptual bias may be influenced by recent exposure to food, which ultimately may affect food intake.

There are several visual dimensions of food that can affect food intake, example portion size, color, and variety. This dissertation elucidates the effect of number of pieces of food on preference and amount of food consumed in humans and motivation for food in animals. Chapter 2 Experiment 1 showed that rats preferred and also ran faster for multiple pieces (30, 10 mg pellets) than an equicaloric, single piece of food (300 mg) showing that multiple pieces of food are more rewarding than a single piece. Chapter 2 Experiment 2 showed that rats preferred a 30-pellet food portion clustered together rather than scattered. Preference and motivation for clustered food pieces may be interpreted based on the optimal foraging theory that animals prefer foods that can maximize energy gain and minimize the risk of predation. Chapter 3 Experiment 1 showed that college students preferred and ate less of a multiple-piece than a single-piece portion and also ate less in a test meal following the multiple-piece than single-piece portion. Chapter 3 Experiment 2 replicated the results in Experiment 1 and used a bagel instead of chicken. Chapter 4 showed that college students given a five-piece chicken portion scattered on a plate ate less in a meal and in a subsequent test meal than those given the same portion clustered together. This is consistent with the hypothesis that multiple pieces of food may appear like more food because they take up a larger surface area than a single-piece portion. All together, these studies show that number and surface area occupied by food pieces are important visual cues determining food choice in animals and both food choice and intake in humans.