This Special Issue of Learning & Behavior, entitled Functional and Ecological Perspectives on Conditioning, commemorates the impressive contributions that Michael Domjan has made to the field of animal learning. It has been our pleasure to work with those who contributed papers, and we are grateful to Editor-in-Chief Jonathon Crystal for his support and guidance. We also would like to acknowledge the early—and especially supportive—efforts of Chana Akins and Robert Bowers to initiate this Special Issue in Learning & Behavior, a journal in which Mike published frequently.

In this Special Issue we examine the impact of Mike Domjan’s research on the influence of a species’ ecology on learning, and, following Tinbergen, how functional questions can be addressed using rigorous experimental methods. The papers in this Special Issue reveal Domjan’s immediate influence on the thinking and problems tackled by investigators, and also a more general trend toward examining the ecological and functional relevance of learning.

Domjan obtained his PhD at McMaster University during a pivotal time in the study of animal learning. The impact of Garcia and Koelling’s landmark paper in 1966 reporting selective associations and long-delay taste-aversion learning were in evidence at McMaster. Domjan was encouraged to explore the implications of these findings by his mentors, including his dissertation chair Shepard Siegel, as well as Herbert Jenkins and Bennet (“Jeff”) Galef. Shepard Siegel’s essay in the Special Issue offers an insightful and personal context to Domjan’s early career.

Domjan’s influential experiments on conditioned taste aversion (CTA) relied on a unique feature of that paradigm. He observed that in CTA the animal initiates contact with the conditioned stimulus (CS), rather than its presentation being fully controlled by the experimenter. This difference between CTA and other examples of Pavlovian conditioning has a significant effect on learning. Domjan developed techniques for presenting taste stimuli while preventing rats from approaching and ingesting food and demonstrated that, when approach and ingestion is bypassed, conditioning is attenuated. Together with other pioneers, like Rozin, Kalat, and Seligman, Domjan’s experiments added to the increased recognition that learning can be understood in terms of its functional and adaptive significance. We see Domjan’s enduring influence on CTA research in Bouton and Michaud’s paper examining partial reinforcement effects on acquisition and extinction.

In 1973, Domjan accepted a tenure-track position at the University of Texas at Austin, where he later developed a unique research program examining Pavlovian conditioning of sexual responses in Japanese quail (Coturnix japonica). He and his collaborators published many papers examining the influence of ecologically relevant conditioned stimuli on conditioned responding. Results from these studies demonstrated how conditioning to an ecologically relevant CS, specifically one with which the subject can physically interact, contradicts predictions stemming from general process learning theories. Several papers in this Special Issue expand on Domjan’s work on sexual conditioning: Arbaiza-Bayona, Arteaga-Avendaño, Puentes-Escamilla and Gutiérrez look at the effect of early social experience on sexual behavior. Akins reviews results from experiments demonstrating unique effects of an ecologically relevant CS on CS and unconditioned stimulus (US) timing parameters in sexual conditioning. Burns-Cusato and Cusato expand findings with quail in their work on reproductive behavior in ring neck doves (Streptopelia risoria), and have reviewed this research in their contribution. Domjan also inspired colleagues to examine some of the clinical implications of conditioning: Dural, Gür, and Çetinkaya explore the persistence of conditioned fear responses and systematically evaluate the role of post-retrieval extinction in the expression of those responses.

With regard to learning, Domjan identified two main perspectives that have guided functional approaches. One, CSs have pre-existing relationships with USs. In nature, CSs are not likely to be completely arbitrary or “neutral,” but instead have some kind of pre-existing relationship to the US. Two, a functional perspective focuses on how learning influences the ways in which the organism interacts with the US, which is biologically most relevant, and less so with the CS. These observations align with the behavior systems approach to learning first identified by Timberlake, and we see the influence of this behavior systems thinking in contributions from Hoffman, Trott, Makridis, and Fanselow, as well as in the articles by Bowers, and Papini. Abts and Dunlap show that rates of forgetting track reliability and value of information in the foraging behavior of bees, with results consistent with a biological preparedness account.

Those who have had the pleasure of getting to know Mike Domjan can attest to the broad ethological scope of his thinking and his passionate pursuit of Tinbergen’s four questions. In honor of this approach, our task as co-editors was to invite contributors who could write about functional and ecological approaches to learning, broadly conceived. Blaisdell and Schroeder offer a functional account to feature binding using a sequence learning procedure in pigeons. Zentall presents intriguing results about how pigeons perceive loss or gain when outcomes are actually the same. This and related work from Zentall’s laboratory offer modern perspectives on classic optimal foraging models. Hollis and Nowbahari reveal how all four of Tinbergen’s aims have furthered our understanding of the rescue behavior of ants. This ethological orientation is also found in Lambert, Sahu, Sturdy, and Guillette, who examine individual variation of cognition in zebra finches.

When we were given the opportunity to edit this Special Issue, we immediately thought of the impressive body of work amassed by Julie Morand-Ferron and her students and collaborators. The goal of this research program has been to combine both field and laboratory experiments in an attempt to understand how a species’ ecology shapes its ability to learn and make decisions. To our delight, Julie accepted the invitation that culminated in the article by Kozlovsky, Poirier, Bertram, and Morand-Ferron. Despite Julie’s tragic death on 13 February 2022, her co-authors persisted; their paper has significance beyond what we would have envisioned from the outset.

Nicolle Matthews-Carr, one of Mike’s doctoral students who published groundbreaking work on the role of conditioning in fertility and sperm competition, offered a wonderfully fitting summarization: “…Domjan’s influence still plays like soft background music in each lecture I give.” Her metaphor is especially apt as Mike’s freedom from the demands of running a research laboratory gave him space to pursue his original passion for music, both performing viola with the orchestra in Austin, TX, and teaching courses about learning and music. This concluding act is a much-deserved delectation after hearing the final, shrill crowing of the last quail to inhabit his laboratory.

We gather that most people who have known and worked with Mike Domjan would not describe him as a “wild man,” so our title requires a bit of explanation. It derives from MK’s fond memory of Mike that took place about 20 years ago. At a lab meeting, participants were discussing a review of Mike’s quail research that he had published in 1998. He entitled it “Going wild in the laboratory: Learning about species typical cues.” As he stared at his copy of the paper, a summary of many years of dedication and hard work, he chuckled, looked up, and softly said “Going wild…I like that title…we’ve gone wild.” Two years ago, a large group of Mike’s former graduate students and post-docs living in many locations worldwide gathered via video conference to hold a reunion “lab meeting.” We surprised Mike with news that we would be assembling this Special Issue to honor him and his research. His immediate and heartfelt response was to deflect all of the credit back to us. It would be impolite to argue with the honoree, but clearly Mike Domjan’s influence on the field of animal learning is extensive and fully deserving of this occasion.