In the behavior and training industry, we use the concept of contrafreeloading a lot, especially with mental stimulation and management. Contrafreeloading is often implemented in enrichment strategies we use for animals we care for. These strategies can help to provide exercise, to promote normal behavior, and allow animals to engage with their environment.


The concept of contrafreeloading was first studied in the 60s with rats. It was found that rats would choose to press a bar for food even when they had free access to the same food nearby (Jensen, 1963). From this, and other research, the term contrafreeloading was developed, technically meaning against getting something without giving anything in return. While we don’t fully understand the mechanisms behind it, there is an innate need or desire to work for food in many species.

Contrafreeloading was initially really surprising as it goes against an ecology theory called the optimal foraging theory. The theory predicts how animals behave when looking for food. In simple terms, it predicts that an animal will always try to maximize fitness, either by expending the least amount of energy to get food, or by trying to get foods that provide the most energy, or both. Working for food, or expending energy to get food, when the same food is freely available, goes against this model.

There have been many speculations for why animals might contrafreeload. Some examples are boredom, different rates of reinforcement, helping animals feel better in an uncertain environment or when they feel uncertain, gathering information about the environment, and attention seeking.

The environment the animal is in can also influence contrafreeloading. As animasl become more hungry and as the effort to get the food increases, they’re less likely to show contrafreeloading (Inglis et al., 1997).


Many studies have looked at a combination of enrichment strategies (including food puzzles or toys) in shelter and kenneled dogs and found improvements in their behavior. For example, one study in shelter dogs found that a combination of frozen Kongs and reinforcement-based training jumped less and were quieter and calmer when meeting potential adopters (Herron et al., 2014). However, the design of those studies does not allow the benefits of the individual types of enrichment to be examined separately. Interestingly, a couple different studies have found that adoptability increased in dogs that have food toys in their kennels, so it seems that people do like to see these offered to dogs.

A small study in kenneled dogs found positive effects with the use of Kongs with treats inside (Schipper et al., 2008). Compared to dogs that did not received Kongs, the dogs had more appetitive behaviors (due to interacting and eating from the toy), increased activity, as well as less barking than their baseline amount.

Not only do dogs seem to like working for their food, it seems like they also experience positive emotions with problem solving opportunities. A study looked at dog behavior as well as heart rate when they were solving different types of puzzles (McGowan et al., 2014). The dogs were trained with puzzles that included things like pressing levers or buttons, or pushing objects, as well as others. In the test phase, some dogs were rewarded with a treat when they correctly solved a new puzzle, where other dogs were given a treat at some point, but it was not in relation to their success with the puzzle. Those that solved the puzzle and received a reward wagged their tails with greater frequency and were more active, and were more excited. Those that randomly received a reward showed signs of frustration in the form of chewing the device.


In a recent study, researchers surveyed cat owners to see how many were using food puzzles (Delgado et al., 2020). They found that 30% of cat owners used puzzles, and another 18% had tried them but were no longer using them. Those that had tried them but weren’t using them were more likely to categorize their cat as ‘lazy’ or ‘dumb’ than those that hadn’t ever tried food puzzles. They concluded that cats failing to interact with toys might affect their owner’s attitude about their intelligence or enrichment interest in a negative way.

There have been numerous benefits shown with the use of food puzzles in case studies in cats, however these have not been shown in research studies as of yet. These include reduced aggression with people and other cats, weight loss, less attention-seeking behaviors, help with litter box avoidance, and decreased anxiety and fear.

While contrafreeloading has been found in many species, including rats, parrots, bears, baboons, and pigs; cats do not readily show this behavior. When given access to a food puzzle as well as a tray containing the same food, indoor cats ate more food from the freely accessible tray. Most cats did eat some food from the food puzzle.

When we apply the use of contrafreeloading to food puzzles or balls, part of the goal is to increase the amount of physical activity they get, in addition to the mental stimulation. However, one study found that this was not the case in cats (Naik et al., 2018). The study cats were fitted with an accelerometer, which measures the amount of activity throughout the day. Cats were fed with a food bowl for a couple weeks and with a food ball for a couple weeks, and their activity was measured. There was no difference in overall daily or weekly activity when the cats were fed with each method. Another study had found that a variety of enrichment opportunities did help with feline weight loss, so it’s an area that still needs to be investigated further.

What does this mean for those working with dogs and cats?

We really don’t have much research in household dogs in terms of contrafreeloading and providing puzzle toys, balls, and other methods of getting food. Due to some of the research in sheltered and kenneled dogs, as well as anecdotal evidence, many do recommend these strategies. Many people with dogs in their home report benefits to these strategies, and it’s really an area where we need more research to find the best strategies for the use of these toys.

In cats, we have less evidence for contrafreeloading, however it’s possible that the motivation, training methods, and other factors are involved.

For animals that we keep in our homes, I still highly recommend the use of puzzle toys, balls, and other methods of feeding, however I don’t recommend making animals work for their entire food allocation for the day.

If you’d like a less technical version of this to share with clients, one can be found at the Landmark Behaviour Blog that is written for pet owners.


Delgado, M., Bain, M.J., Buffington, C.A.T. 2020. A survey of feeding practices and use of food puzzles in owners of domestic cats. Journal of Feline Medicine and Surgery, 22:193–198.

Herron, M.E., Kirby-Madden, T.M., Lord, L.K. 2014. Effects of environmental enrichment on the behavior of shelter dogs. Journal of the American Veterinary Medical Association, 244: 687–692.

Jensen, E. D. 1963. Preference for bar pressing over free-loading as a function of number of unrewarded presses. Journal of Experimental Psychology, 65:451–454.

McGowan, R.T.S., Rehn, T., Norling, Y., Keeling, L.J. 2014. Positive affect and learning: exploring the ‘‘Eureka Effect’’ in dogs. Animal Cognition, 17:577-587.

Naik, R., Witzel, A., Albright, J.D., Siegfried, K., Gruen, M.E., Thomson, A., Price, J., B., Lascelles, B.D.X. 2018. Pilot study evaluating the effect of feeding method on overall activity of neutered indoor pet cats. Journal of Veterinary Behavior. 25:9-13.

Schipper, L.L., Vinke, C.M., Schilder, M.B.N., Spruijt, B.M. 2008. The effect of feeding enrichment toys on the behaviour of kennelled dogs (Canis familiaris). Applied Animal Behaviour Science 114:182–195.