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

Abstract

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.

Intact vagal gut‐brain signalling prevents hyperphagia and excessive weight gain in response to high‐fat high‐sugar diet

“…To determine whether CCK‐SAP‐treated rats are more motivated to consume palatable HFHS diet, we tested the willingness of the animals to work for the taste of fat or sugar. The same lean chow‐fed SAP or CCK‐SAP‐treated rats were trained to lick for equicaloric solutions of 10% fat or 20% sucrose before performing a progressive ratio licking task, 72 in which exponentially increasing numbers of licks were required for either fat or sugar delivery. The breakpoint, the point at which the animals ceased licking the dry sipper to get the reward, presented as the last reward achieved, was used to determine the willingness of the animals to work for fat or sugar.…”

Making Sense of Rodent Models of Anhedonia

“…As previously noted, we tend to infer “liking” from a choice the animal makes or from the willingness to operate to obtain a stimulus, but we do not have a direct measure of it. Similarly, we do not know whether a stimulus does or does not retain hedonic properties for the animal that stops responding in the PR schedule ( Der-Avakian et al, 2016 ; Kissileff and Herzog, 2018 ). Thus, as suggested in the Introduction, the 2 aspects that sustain behavioral responses toward primary rewards are closely intertwined.…”

Significant association of nicotine reinforcement and cue reactivity: a translational study in humans and rats

“…It is difficult to dissociate drug 'wanting' and 'liking' with commonly used laboratory tasks, performance is likely to be determined as a function of both A u t h o r s A c c e p t e d V e r s i o n motivational and hedonic value. However, PR schedules have been considered to be more likely to measure motivational 'wanting' rather than hedonic 'liking' because motivation requires action whereas pleasure is experienced more passively (Kissileff & Herzog, 2018). Similarly, forced-choice tasks have been used to index explicit 'wanting' (Finlayson, King, & Blundell, 2007).…”