Toggle Main Menu Toggle Search

Open Access padlockePrints

Free food or earned food? A review and fuzzy model of contrafreeloading

Lookup NU author(s): Dr John Lazarus


Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


Animals will work (e.g. lever press) for 'earned' food even though identical 'free' food can easily be obtained from a nearby dish. This phenomenon, called contrafreeloading, appears to contradict a basic tenet of most learning, motivation and optimal foraging theories; namely that animals strive to maximize the ratio of reward, or benefit, to effort, or cost. This paper reviews the factors that have been found to affect the level of contrafreeloading, to try to explain the behaviour. In experiments involving intensive training, contrafreeloading may be explained on the basis of secondary reinforcement and/or differential exposure to the alternative food sources. However, contrafreeloading also occurs without prior training. Contrafreeloading declines with increasing hunger and with increases in the effort required to obtain the earned food: it also has an inverted-U relationship with the degree of stimulus change associated with the earned food. A fuzzy logic model is developed to predict the outcome of interactions between these factors. The model successfully simulates previous empirical findings and provides novel, testable predictions. It is argued that contrafreeloading does not contradict reinforcement theory, provided that the sensory reinforcement obtained from stimuli associated with the earned food is also taken into account. A functional explanation of why such stimuli are reinforcing, and of contrafreeloading itself, is based upon the advantage of gathering information for animals living in changing environments (i.e. an information primacy model). Animals work for earned food in order to update their estimate of a currently sub-optimal food source because, in the longer term, it may unpredictably become the optimal place to feed. Contrafreeloading is therefore a behaviour that, under natural conditions, is adaptive.

Publication metadata

Author(s): Inglis IR, Forkman B, Lazarus J

Publication type: Article

Publication status: Published

Journal: Animal Behaviour

Year: 1997

Volume: 53

Issue: 6

Pages: 1171-1191

Print publication date: 01/06/1997

ISSN (print): 0003-3472

ISSN (electronic): 1095-8282

Publisher: Elsevier Ltd


DOI: 10.1006/anbe.1996.0320


Altmetrics provided by Altmetric