Clicker training in laboratory rodents

Animals have been trained by humans for more than 10,000 years for a variety of purposes. Training based on conditioned reinforcement, which includes clicker training, has recently gained popularity. The use of a clicker in combination with food to confirm desired behavior has been proven especially in dog training as well as in horse riding.¹

Classical conditioning, the basis of any clicker training, was first described in the 19th century by its founder, learning theorist Ivan Pavlov. He recognized in his behavioral experiments on dogs that a neutral stimulus, supplemented by a conditioned reflex, can become a conditioned stimulus. Pavlov referred to the dogs' salivation upon perception of food - an unconditioned stimulus - as a reflex or unconditioned/or innate response. The bell sounding in connection with feeding (neutral stimulus) was linked by the dogs to eating in a learning process and then led to increased salivation, conditioned response, even in the absence of food stimulation. Thus, the bell is to be understood as a conditioned (learned) stimulus. Clicker training, in which food is associated with a clicking sound, is based on the principles of Pavlov's learning theories.²

The founder of operant conditioning, B. F. Skinner, continued Pavlov's research in the 20th century. Using his clicker experiments with rats, he was able to prove that behavior can be reinforced by positive reinforcement and is thus more likely to occur. For this purpose, a learned, i.e., conditioned, reinforcer is used.²

Leidinger et al. prove in their study that the use of a clicker for positive reinforcement can be of great benefit in training on mice. As cognitive enrichment, clicker training contributes to the improvement of the animals' well-being and thus partly fulfills the goal of refinement, which, along with replacement and reduction, is a central element in the EU Directive applicable to animal experiments (RL 2010/63/EU). Furthermore, training the mice leads to habituation of the animals to the experimenter, which reduces stress. Leidinger et al. in their publication entitled "Introducing Clicker Training as a Cognitive Enrichment for Laboratory Mice" present a protocol for implementing training using a clicker on mice. She said it is important to use preference tests to find out which food provides the greatest stimulus for the animals before beginning the training sessions. Treats such as nuts, fruit, jam, gummy bears or chocolate are good rewards. Already within the first training sessions, the mice are conditioned to the clicker by linking the click with a treat. In the last sessions of clicker training, they should be gradually habituated to the experimenter's hand.³

After completion of all training sessions, the mice were compared with untrained control animals with regard to their anxiety or stress behavior. Indeed, clicker training graduates exhibited behaviors such as urinary and/or fecal dropping or vocalization to a lesser extent during handling. In the Morris Water Maze test, the animals were likewise less stressed, as indicated by a significantly lower frequency of squealing as well as a lower tendency to drift. Thus, their study demonstrated the positive influence of clicker training on human-animal interaction.⁴

Dickmann et al. used the same clicker training protocol in their behavioral study of mice. Based on the performance of the trained compared to the untrained animals in the Cat Walk, Open Field, and Elevated Plus Maze tests, a measurable difference can be seen. For example, the speed and distance traveled in the test systems used showed clear differences between the two test groups, but especially among the female test animals.⁵

In another study by Leidinger et al. the research group deals with clicker training in rats. Their goal is to avoid handling during transfer in order to reduce stress levels in the animals and the potential hygiene risk from direct human-animal contact. Stress is known to have a negative impact on the well-being of laboratory animals and likewise affects reproducibility and consequently the quality of research. Leidinger et al. present their training protocol to teach rats to change cages independently and voluntarily using a clicker. Since rats are naturally curious and inquisitive animals, clicker training is not a major hurdle. In their experiment, a part of the group that was not included in the training even learned the desired behavior purely by observing the procedure.⁶

Clicker training benefits both the animals and the research and involves only a small and manageable amount of additional time. Likewise, the training strengthens the human-animal relationship. Thus, the implementation of clicker training can be considered useful from many points of view and should therefore be strived for by animal testing facilities in the future in terms of refinement.

1) Pfaller-Sadovsky N, Hurtado-Parrado C, Cardillo D, Medina LG, Friedman SG. What's in a Click? The Efficacy of Conditioned Reinforcement in Applied Animal Training: A Systematic Review and Meta-Analysis. Animals (Basel). 2020 Sep 28;10(10):1757. doi: 10.3390/ani10101757. PMID: 32998242; PMCID: PMC7600771. Diamond J. Evolution, consequences, and future of plant and animal domestication. Nature 2002, 418, 700–707.
2) https://zuugs.hfh.ch/verhalten/chapter/klassische-lerntheorien/ (Zugriff am 26.04.2023) Skinner B F. How to Teach Animals. Sci. Am. 1951, 185, 26–29. Available online: https://psycnet.apa.org/ record/1952-04212-001 (accessed on 8 July 2020).
3) Leidinger C, Herrmann F, Thöne-Reineke C, Baumgart N, Baumgart J. Introducing Clicker Training as a Cognitive Enrichment for Laboratory Mice. J Vis Exp. 2017 Mar 6;(121):55415. doi: 10.3791/55415. PMID: 28287586; PMCID: PMC5408971. RL 2010/63/EU Balcombe J P, Barnard N D, Sandusky C. Laboratory routines cause animal stress. Contemporary topics in laboratory animal science / American Association for Laboratory Animal Science. 43 (6), 42-51 (2004).
4) Leidinger C, Herrmann F, Thöne-Reineke C, Baumgart N, Baumgart J. Introducing Clicker Training as a Cognitive Enrichment for Laboratory Mice. J Vis Exp. 2017 Mar 6;(121):55415. doi: 10.3791/55415. PMID: 28287586; PMCID: PMC5408971.
5) Dickmann J, Gonzalez-Uarquin F, Reichel S, Pichl D, Radyushkin K, Baumgart J, Baumgart N. Clicker Training Mice for Improved Compliance in the Catwalk Test. Animals. 2022; 12(24):3545. https://doi.org/10.3390/ani12243545
6) Leidinger C S, Kaiser N, Baumgart N, Baumgart J. Using Clicker Training and Social Observation to Teach Rats to Voluntarily Change Cages. J. Vis. Exp. (140), e58511, doi:10.3791/58511 (2018).