Progressive ratio (PR) schedules and the sipometer: Do they measure wanting, liking, and/or reward? A tribute to Anthony Sclafani and Karen Ackroff.

This paper honors the contributions made by Anthony (Tony) Sclafani and Karen Ackroff to both the Columbia University Seminar on Appetitive Behavior and to the field of ingestive behavior in general. We review their use of the progressive ratio (PR) licking paradigm, to determine whether the taste of sucrose, independent of its post-ingestive effects, is always positively reinforcing in animals. They demonstrated a monotonic increase in licking as concentration increased, and obtained results identical to those obtained with a lever-pressing paradigm, but licking was easier and more natural than lever pressing. The PR paradigm was translated to evaluate liquid food reward value in humans. An instrument (the sipometer) was devised that initially permitted a few seconds access to small amounts of a sweet beverage as the participants increased the time to obtain it in 3-5-sec increments. The device went through two refinements and currently delivers the reinforcer and measures the pressure exerted to obtain it. The sipometer is compared with other techniques for measuring motivation and reward. The use of the sipometer and the PR method are discussed in relation to the theoretical challenges inherent in measuring motivation and pleasure, from both psychological and behavioral economics perspectives, and why it is or is not important to separate these processes for both theoretical and practical applications.

Kissileff HR ，Herzog M 《-》

A sipometer for measuring motivation to consume and reward value of foods and beverages in humans: Description and proof of principle.

New methods, derived from animal work, for measuring food reward value (i.e. reinforcing value of food), and motivation (i.e. strength of desire) to consume, in humans are described and validated. A sipping device (sipometer) was developed that permits access to a liquid food or beverage on two reward schedules: continuous reinforcement (CR) and progressively increasing time spent exerting pressure on a straw (PR-schedule). In addition, a pictorial scale showing a cup, from which the 'amount wanted' could be marked was used to pre-test potential consumption. Intake, time spent sipping, breakpoint, and pressure exerted were the main dependent variables measured. Three pilot experiments were conducted. In Experiment 1, participants (n=8) consumed yogurt shakes after a 1-h or 21-h food deprivation period on both schedules. In Experiment 2, participants (n=8) sham-consumed (i.e. spit out) sweet and non-sweet beverages, utilizing both schedules. In Experiment 3, sham-consuming sweet and non-sweet beverages on both schedules and working for shake on the PR schedule were repeated, after three nights of either habitual sleep or short sleep duration (n=7) in a crossover design. In Experiment 1, participants sipped longer after 21-h vs. 1-h of food deprivation (13±3.0 vs. 8.0±2.1s; p=0.04), on the PR schedule. In Experiment 2, sham-intake (p=0.01) and sipping time (p=0.04) were greater for sweet than non-sweet beverages on the PR schedule and a similar, though not conventionally significant, effect was observed for exerted pressure (p=0.09). In both Experiment 2 and Experiment 3 after habitual sleep, on the PR schedule, cumulative pressure difference between sweet and non-sweet beverage increased with difference in amount wanted in the taste test. In contrast, after short sleep participants were less willing to work for sweet taste as their wanting increased, suggesting that sleep deprivation raises desire, but lowers behavioral output. Taken together these results demonstrate that the sipometer and associated ratings are reliable and useful measures of motivation to consume and reward value in humans. Participants were more motivated to obtain access to sweet beverages, especially when these were better liked than to obtain access to non-sweet beverages.

Hogenkamp PS ，Shechter A ，St-Onge MP ，Sclafani A ，Kissileff HR ... -  《-》

Is it possible to dissociate 'liking' and 'wanting' for foods in humans? A novel experimental procedure.

Finlayson G ，King N ，Blundell JE 《PHYSIOLOGY & BEHAVIOR》

Reinforcement value of sucrose measured by progressive ratio operant licking in the rat.

Sclafani A ，Ackroff K 《PHYSIOLOGY & BEHAVIOR》

"You Say it's Liking, I Say it's Wanting …". On the difficulty of disentangling food reward in man.

According to the influential theory of Berridge (1996, 2009), food reward comprises two components: food 'liking' and 'wanting', with 'liking' referring to the pleasure derived from eating a given food and 'wanting' referring to appetitive motivation. Animal research shows that these two components have separate neural correlates. In examining reward driven eating in man, researchers have thus begun to develop interest in indicators of 'liking' and 'wanting'. But validating 'liking' and 'wanting' requires the dissociation of these components when theory dictates they should diverge. One such circumstance is neural sensitization as this leads to exaggerated 'wanting' without increased 'liking'. However, there are no data suggesting that such sensitization is the likely result of (over)eating. Without sensitization, one cannot determine whether task performance is indicative of true food 'liking' or 'wanting'. It is concluded that it is important to assess appetite and palatability in the study of reward driven eating, but determining whether these measurements reflect either food 'wanting' or food 'liking' is not.

Havermans RC 《-》