Learning & Behavior - A special issue honoring Ken Cheng: navigating animal minds
Ken Cheng, Comparative Cognition Society Research Award Recipient, performing ‘Sunrise, Sunset in Science’ at the 2023 Comparative Cognition conference, Melbourne, Florida, USA (photo: C.A.F.)
It has been our great pleasure to edit this Special Issue honoring the many outstanding contributions of Dr. Ken Cheng to the field of comparative cognition and beyond. Ken was selected by the Comparative Cognition Society to receive the 2023 research award, which honors scientists who have made outstanding contributions to our understanding of animal cognition. He was invited to present the master lecture at the 2023 Conference of the Comparative Cognition Society, where he not only provided intellectual stimulation that stretched our minds, but also provided entertainment in the form of a song he wrote about young minds and the passage of time in academia, wonderfully performed by Ken and several of his brave colleagues. The conference also included a symposium featuring work from his colleagues and former students, and a banquet in his honor, where there was more singing and a lot of fun.
Ken started his career with a wide-ranging education, obtaining a BSc in Psychology from the University of Toronto (1978), followed by a Master’s in Education from Harvard (1980). He returned to psychology, obtaining a PhD from the University of Pennsylvania (1984), where he worked with Prof. C. Randy Gallistel. He held postdoctoral and research fellowship positions at Sussex University (where he studied navigation in bees with Prof. Collett), the University of Western Ontario (where he studied timing behaviour and spatial learning in collaboration with Profs. William Roberts and David Sherry), and then held a research associate position at the University of Toronto (where he studied spatial learning and memory in collaboration with Prof. Shettleworth). He then moved to Australia where he is currently a Professor at Macquarie University, becoming fascinated with the navigational abilities of the red honey ant (Cheng et al., 2009) and later navigation in low light in the nocturnal bull ants on the Macquarie campus (Freas et al. 2018; Freas & Cheng, 2019; Islam et al., 2020; Lionetti et al., 2023, this issue), both of which he works with to this day.
The geometric module
Ken’s impact on comparative cognition began early in his career with his dissertation work conducted in the lab of his supervisor Dr. Gallistel. Ken’s most well-known work began inauspiciously, with initial failure and frustration. Attempting to characterise the effect of changes to a rectangular arena on the rats’ spatial performance, the test rats were inexplicably equally confused in both the experimental and control conditions. Yet, the answer proved most interesting indeed, with Ken discovering the rats were performing poorly in the control due to systematic errors, with individuals searching the diagonally opposite location of the target site. This epiphany led to Ken’s most well-known paper (Cheng, 1986) where he demonstrated, with creative experiments, that rats process the shape of an enclosed environment (i.e., relative wall lengths and the relationship between them) for navigation back to a desired location. Most interesting was his finding that rats would fail to use other features within the environment to disambiguate geometrically equivalent locations in a rectangular arena. This led him to propose that rats may possess an encapsulated geometric module that processes the shape of the environment independently of other features within the environment.
Ken’s dissertation research, and his proposal of a geometric module, inspired extensive research in comparative spatial cognition, with subsequent studies showing that geometric shape is encoded for spatial navigation by countless other organisms including invertebrates (Wystrach & Beugnon, 2009), fish (Sovrano et al., 2002), birds (Kelly et al., 1998), nonhuman primates (Gouteax et al., 2001), and humans (Hermer & Spelke, 1996; see review by Cheng et al., 2013). As nicely discussed in the review paper by Newcombe (2023, this issue), his ideas not only expanded the field of comparative spatial cognition, but also led to lively debate in other fields, including developmental psychology. Moreover, the importance of geometric shape in place finding has impacted research in neuroscience, as discussed by Jeffery (2023, this issue). Yet this contribution did come at a price. Unfortunately for Ken, this marked the end of his work with rats as he became dreadfully allergic and has avoided working with them since.
Ant navigation
Ken first laid eyes upon the ant that would become his main study species for the next 20 years in the visitor’s centre parking lot of Simpson’s Gap, a reserve in the West McDonnells mountains just to the west of Alice Springs. Ken was on a reconnaissance trip to Australia’s red centre with Rüdiger and Sybille Wehner, to find the most thermophilic ant in Australia, the red honeypot ant (Melophorus bagoti). This quick, solitarily foraging ant has since become the focus of much of Ken’s research on visual navigation in insects.
The contributions that Ken has made to our understanding of how these tiny navigators both find food sites and then return to the nest could fill a book, so here we will briefly mention some impactful examples. Much of the work in M. bagoti revolves around their habitat, a semi-arid desert with plentiful visual cues in the form of grass, bushes, trees, and even distant mountains. As illustrated by some clever work in Ken’s lab, it is the skyline, where these terrestrial cues meet the sky, which is a critical component for how ants navigate via views (Graham & Cheng, 2009; Schultheiss et al., 2016). The use of visual landmarks that comprise panorama- or view-based guidance in ants is a critical aspect of Ken’s work with the Australian red honeypot ant, as the presence of these cues within the ant’s habitat leads to a drastic change in how ant navigators’ weight different information streams in comparison to ants that forage in featureless environments (Cheng et al., 2009). This work has greatly expanded our understanding of panorama guidance, route following (Wystrach et al., 2012), search behaviour (Schultheiss & Cheng, 2011), navigational learning in ants (Freas and Cheng, 2018; Freas et al., 2017, 2019; Wystrach et al., 2020), and how navigation can be accomplished with a toolkit of servomechanisms (Freas & Cheng, 2022b; Cheng, 2022b, 2023b)
Current interests: Cognition and oscillations across life
Ken’s breadth of interests spans a huge range of organisms and topics in comparative cognition. He has published extensive research on a wide range of animals, including rodents, humans, and several species of birds and insects. His recent interests have expanded beyond traditionally studied species to the wealth of cognition that occurs beyond the brain, including both embodied or situated cognition (Cheng, 2018) and copious evidence of learning occurring in ‘brainless’ animals, including Cnidaria (Cheng, 2023a), Echinodermata (Freas & Cheng, 2022a), memory in slime molds (Cheng, 2022a), and spanning all forms of life from microbes (Lyon & Cheng, 2023) to artificial agents (Cheng, 2019). Within this broad range of interests, Ken has lately become fascinated by how widespread oscillations are across all lifeforms, and integrating these units of action into navigational movement (Cheng, 2022b, 2023b; Freas & Cheng, 2022b).
Although most of Ken’s work has focussed on various aspects of spatial learning and navigation, he has also made important contributions to the understanding of many other cognitive and behavioural processes, including timing behaviour (e.g., Cheng & Roberts, 1991; Cheng et al., 1993; Cheng et al., 1996), perception (Cheng & Spetch, 2002; Evans et al., 2000) and education (Jalava et al., 2023), to name just a few. Many of his ideas, such as the notion that information from different sources may be integrated in a Bayesian fashion (Cheng et al., 2007), continue to impact research and theory not only in comparative cognition but also in human spatial cognition (e.g., Newman et al., 2023). Perhaps even more important than the breadth of his contributions to the field, is his dedication to integrating ideas across fields such as (but not limited to) behavioural ecology, comparative cognition, neuroethology and neuroscience (see Bingman & Cheng, 2005; Cheng, 2006, Cheng et al., 2009; Cheng & Jeffery, 2017; Deeti et al., 2023; Perry et al., 2013). Right from his early days when he brought ideas from mathematics and neuroscience into his research on rats, he brings ideas from other disciplines into the study of comparative cognition, and he also exports knowledge from psychology to other domains such as education, artificial intelligence and neuroscience.
This issue
This collection of articles includes work by those who have had the pleasure of working with Ken, as students, post-doctoral fellows, and a long list of collaborators. We have all been inspired by his ideas, his approach to understanding behaviour and the mind, and by his enthusiasm for science. The issue is thematically divided, with the first portion focusing on Ken’s contributions during his early work with the geometric module, mammalian and avian spatial cognition, and time intervals. We begin with a tribute to Ken’s geometric module ideas and their influence in developmental psychology by Nora Newcombe (Newcombe, 2023, this issue). Next is an article by Kate Jeffery, which reviews current ideas and neuroscience research on the structure of the mammalian cognitive map and illustrates Ken’s influence on neuroscience (Jeffery, 2023, this issue). Her article concludes that the cognitive map functions to support adaptive behaviour and is tailored to species and environments, much in keeping with Ken’s approach to cognition. This is followed by two papers by early collaborators of Ken. Jonathon Crystal explores the temporal fundamentals of episodic memory (Crystal, 2023, this issue), with a central role given to biological oscillators, a process also given much importance in Ken’s recent work (Cheng, 2022b, 2023b). William Roberts’ article fits within the tradition of careful and creative experimentation exemplified by Ken’s work, here concerning rat spatial memory (Roberts et al., 2023, this issue). This section concludes with a piece by Bingman and Gagliardo which highlights Ken’s promotion to study spatial cognition and navigation in the field under natural conditions (Bingman & Gagliardo, 2023, this issue).
The second group of articles primarily highlights Ken’s work on ant navigation and its implications for animal cognition, with articles focusing on many of his primary contributions to the field. We begin with an article by Sebastian Schwarz, Antoine Wystrach, Ken Cheng and Debbie Kelly, exploring the use of landmark beacons and panoramic views as navigational cues in pigeons (Schwarz et al., 2024, this issue). Next, Patrick Schultheiss presents a continuation of his work characterising search behaviour in the presence of unbalanced visual cues (Schultheiss, 2023, this issue), expanding an aspect of search he spearheaded while a student of Ken’s. We follow this with an article from Ken’s lab by his most recently completed PhD student, Dr. Vito Lionetti, who explores navigation in three dimensions in the nocturnal bull ant, M. midas, characterising the accumulation of the path integrator and aversive view memories while ants are positioned vertically when ascending their foraging tree (Lionetti et al., 2023, this issue). The next article by Barrie et al. (2023, this issue), characterises the formation of visually guided route formation in the presence of social cues (chemical trail information), suggesting that individual-based visual cues are the dominant cue for route following. We conclude with our own article, which showcases Ken’s influence on the field of ant navigation, exemplifying the importance of exploring comparative cognition across species. Here, we show that the trail following Western thatching ant (Formica obscuripes) relies on both individual and social cues in combination to navigate, with the pheromone acting as a non-directional verification cue. This work (Freas & Spetch, 2023 this issue) aligns with Ken’s assertions (Cheng et al., 2014) that each ant species’ navigational toolkit is tuned to its habitat and foraging ecology.
Conclusion
We hope this collection of articles provides a glimpse into the truly monumental impact that Ken has had on the field of comparative and spatial cognition. Ken’s research over the years has provided a wealth of discoveries concerning how animals move through and learn spatial cues, and has been foundational to how we currently understand spatial cognition. Furthermore, his training and mentorship of a new generation of scientists ensures that his impact will continue well into the future.
Data Availability
No new data were created/analysed for this manuscript.
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Funding
Funding was provided by the Canadian Natural Sciences and Engineering Research Council to MLS and CAF (#2020-03933) and a Macquarie University Research Fellowship to CAF (MQRF0001094).
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Authors and Affiliations
School of Natural Sciences, Macquarie University, Sydney, NSW, Australia
Cody A. Freas
Department of Psychology, University of Alberta, Edmonton, Alberta, Canada
Marcia L Spetch
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Correspondence to Cody A. Freas (this opens in a new tab).
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