Physical Causal Cognition in Parrots Doctoral thesis for obtaining the academic degree Doctor of Natural Sciences submitted by Laurence O’Neill at the Faculty of Sciences Department of Biology Konstanz, 2020 1 Konstanzer Online-Publikations-System (KOPS) URL: http://nbn-resolving.de/urn:nbn:de:bsz:352-2-2r13ubpt9miv6 Date of the oral examination: 07/08/2020 1. Reviewer: Dr. Dina Dechmann 2. Reviewer: Prof. Dr. Manfred Gahr 2 Contents Summary ................................................................................................................................... 5 Zussamenfassung ...................................................................................................................... 7 1 General Introduction ..................................................................................................... 9 1.1 Causal cognition .........................................................................................................11 1.2 Parrots ........................................................................................................................18 1.3 Parrots as a model in comparative cognition and the selection of a study species ......23 1.4 How to test causal cognition .......................................................................................27 1.5 Experimental plan .......................................................................................................37 2 Chapter 1 - Primate Cognition Test Battery in Parrots .................................................39 2.1 Abstract ......................................................................................................................40 2.2 Introduction .................................................................................................................41 2.3 Materials and Methods ................................................................................................45 2.4 Results ........................................................................................................................52 2.5 Discussion ..................................................................................................................58 3 Chapter 2 - Two macaw species can learn to solve an optimised two-trap problem, but without functional causal understanding ....................................................................................72 3.1 Abstract ......................................................................................................................73 3.2 Introduction .................................................................................................................74 3.3 Methods ......................................................................................................................78 3.5 Discussion ..................................................................................................................85 4 Chapter 3 - Causal Understanding of the Stone Dropping Task in Two Species of Macaw .................................................................................................................................... 101 4.1 Abstract .................................................................................................................... 102 4.4 Results ...................................................................................................................... 114 4.5 Discussion ................................................................................................................ 116 5 General Discussion ................................................................................................... 130 5.1 Summary of Primate Cognition Test Battery (PCTB) in Parrots ................................. 130 5.2 Summary of the Trap-table test ................................................................................. 133 5.3 Summary of Stone dropping ..................................................................................... 137 5.4 To what extent do parrots show causal understanding? ............................................ 142 5.5 Psychometrics in causal cognition tests .................................................................... 144 6 Overall Conclusions .................................................................................................. 147 3 7 References ................................................................................................................ 148 8 Author Contributions .................................................................................................. 161 9 Ethical Statement ...................................................................................................... 162 10 Acknowledgments ..................................................................................................... 163 4 Summary The study of comparative cognition aims to elucidate the evolution of different domains of cognition. By comparing and contrasting closely and distantly related species we can identify the selective pressures that may have lead to their specific cognitive traits. Causal cognition is considered a more complex cognitive trait and is defined as how individuals understand cause and effect relationships. Causal relationships can be learned associatively, but there also appears to be some species that have an intuitive understanding of the mechanisms that underlie causal relationships. Parrots represent a relatively understudied and diverse group of birds that display complex cognitive traits. Studying causal cognition in parrots therefore provides information on a broad range of species that are adapted to a varied range of niches, which vastly broadens our perspective of cognitive evolution. I studied whether different species of parrots were capable of using understanding of causal relationships to guide their behaviour, and specifically whether this causal understanding was driven by learned associations or by complex cognitive processes based on underlying mechanisms. I tested four species of parrots from the Psittacidae family: three species from the Arinae subfamily, Ara ambiguus (great green macaws), Ara glaucogularis (blue throated macaws) and Primolius couloni (blue headed macaws), and one species from the Psittacinae subfamily, Psittacus erithacus (African grey parrot). In the first chapter I tested all four species on an established test battery to evaluate a broad range of cognitive factors from both the physical and social domain. I was able to compare the parrots’ results to both apes and monkeys that had previously completed the same test battery. The parrots did poorly, but it was likely due to issues with task design that made the tests especially difficult for the parrots compared to primates. Following this, in the second chapter, I tested the two Ara species on an established causal cognition test: the trap-tube. Although many subjects were relatively successful in the task, the macaws showed a preference to use learned rules to find a solution rather than an understanding based on the underlying mechanism of the apparatus. Finally, in the third chapter, I once again tested the two Ara species in another causal cognition test: the stone- dropping task. There was a division between the two Ara species in their approach to solve the task. It appears that most of the Ara ambiguus were able to solve the task through exploratory behaviour alone whereas the Ara glaucogularis appeared to require information on the underlying mechanism of the apparatus to solve it. 5 The first two chapters entailed choice tasks, where subjects were required to pick between two or three options to find a reward. I discuss how this type of testing is not suitable for exploring aspects of complex cognition as most subjects can solve these tasks using simple learned rules. However, based on results of the second chapter, I discuss how if choice tests must be used then there are ways to improve subjects’ motivation to not use simple learned rules. Based on the results of the third chapter, I was able to discuss in more detail what kind of causal understanding the two Ara species used. I came to the conclusion that although they may have the capacity to use causal understanding based on the underlying mechanisms of apparatuses, they do not appear to have a drive to do so, favouring learned causal associations where possible. Finally, I contextualise these results on what we know about these parrots ecology and suggest that a causal understanding based on functional mechanisms may not be a factor that is especially vital for macaw cognition. 6 Zussamenfassung Das Studium der vergleichenden Kognition zielt darauf ab die Evolution von verschiedenen Domänen der Kognition aufzuklären. Indem wir nah und entfernt verwandte Arten vergleichen und gegenüberstellen, können wir mögliche Selektionsdrucke identifizieren, welche zu artspezifischen kognitiven Anpassungen geführt haben könnten. Kausale Kognition wird als eine komplexe kognitive Fähigkeit eingestuft und definiert sich als ein Verständnis des Zusammenhang zwischen Ursache und Wirkung. Kausale Zusammenhänge können assoziativ erlernt werden, aber es scheint, dass gewisse Arten ein intuitives Verständnis des zugrundeliegenden Mechanismus von kausalen Zusammenhängen haben könnten. Papageien repräsentieren eine nur mäßig untersuchte und diverse taxonomische Gruppierung von Vögeln, die komplexe kognitive Fähigkeiten aufweisen. Das Studium von kausaler Kognition