Field of Comparative Psychology, The
A multidisciplinary field that examines the similarities and differences in the behavior of organisms with special emphases on the development and evolution of the behaviors.
Modern comparative psychology, one of the interdisciplinary fields in psychology, developed from the convergence of a number of separate disciplines including ethology, behavioral ecology, psychology, systematics, and genetics (Gariépy 1998). Examining questions of functional adaptiveness, development, and evolution of behavior, comparative psychology incorporates all aspects of a living being: anatomy and physiology, genetics, affect, cognition, and sociality. This diverse field explores questions of behavior, behavioral development, cognition, communication, emotion, learning, mating, memory, motivation, perception, social relationships, spatial navigation and orientation, parental behavior, and many other specific topics. Comparative psychology incorporates a specific method of investigation in which multiple species are compared systematically to address various questions about evolution and shared phylogeny.
References in which the history of comparative psychology is described generally point to the publication of Charles Darwin’s (1809–1882) two most influential books, On the Origin of Species (1859) and The Expression of the Emotions in Man and Animals (1872), as the pivotal moments in which animal behavior was brought into mainstream science (e.g., Greenburg and Haraway 1998; Siiter 1999; Slater 1999). Focused on the importance of the similarities in physical, behavioral, and emotional attributes of individuals of common descent, Darwin’s ideas impacted the fields of biology and psychology.
This fledgling field of animal behavior was expanded by George John Romanes (1848–1894), a British naturalist and staunch admirer of Charles Darwin and his ideas. Romanes applied Darwin’s idea of evolution and its mechanism of natural selection to mental processes, including higher-order thinking (e.g., planning, comparing, and contrasting), proposing that intelligence ranged in complexity from the least complex animals to the most complex animals (i.e., humans) (Gariépy 1998; McInnis 1998; Siiter 1999). This gradient approach to the spectrum of mental abilities across species influenced the fields of learning, comparative cognition, and developmental psychology. A proponent of the anecdotal method, Romanes developed his hypotheses from individual pieces of evidence obtained from firsthand experiences, secondhand stories, or descriptions of interesting and clever behavior across many species of animals. Unfortunately, this data collection method is subject to inherent biases as humans often attribute human characteristics to animals (i.e., anthropomorphism), endowing animals with characteristics that may be more than necessary.
C. Lloyd Morgan (1852–1936), a British psychologist, close friend, and critic of Romanes, emphasized the importance of objectivity and empiricism when interpreting animal behavior. While agreeing with the possibility that mental processes also evolved, Morgan reminded early and future comparative psychologists to avoid explaining behavior using higher mental processes when lower-level psychological processes could account for the behavior (Gariépy 1998; Greenberg and Haraway 2002; McInnis 1998; Siiter 1999). This rule is known as Morgan’s Canon as Morgan was the first to apply this idea of parsimony to animal behavior (Siiter 1999).
Following this early venture into comparative psychology and the importance of comparing different animal species using objective, empirical methods, the psychology-based field of behaviorism advanced comparative psychology. Focused on uncovering the general principles of learning and motivation, behaviorists such as Ivan Pavlov (1849–1936), Edward Thorndike (1874–1949), and John B. Watson (1878–1958) continued to utilize characteristics of comparative psychology by emphasizing the specific mechanisms and the development of behavior (Greenberg and Haraway 2002; Siiter 1999). Although the era of behaviorism examined learning and motivation in several species (e.g., rats, Rattus norvegicus; dogs, Canis lupus familiaris; cats, Felis catus), the behaviorists were heavily criticized for their lack of diversity in topics and species (reviewed by Gariépy 1998; Greenberg and Haraway 2002).
While comparative psychology was growing in America, the field of ethology was emerging from biology, led by Konrad Lorenz (1903–1989), Nikolaas “Niko” Tinbergen (1907–1988), and Karl von Frisch (1886–1982), among others. Emphasizing the importance of instinct or innate behaviors, biological explanations, and naturalistic field studies, ethologists focused on the adaptiveness of particular behaviors and the evolution of those behaviors (Greenberg and Haraway 2002; Siiter 1999).
Anthropomorphism is the attribution of human qualities to nonhuman animals. Early studies in comparative literature relied heavily on anecdotal evidence of humanlike behavior in animals. Scholars such a Romanes and Buchner focused on three main areas: complex reasoning, social behavior, and social emotions (such as sympathy, shame, jealousy, and humor). Lloyd Morgan’s Canon (1894) emphasized parsimony, urging scientists to limit their conclusions to the psychologically simplest process consistent with the data. With Morgan’s Canon, anthropomorphic explanations were viewed with more skepticism but still held a place in the field. It was during the 1920s, with the rise of behaviorism and the biological perspectives of ethology, that anthropomorphism started to be viewed as unscientific and even a fallacy of reasoning. Animal behavior research and ethology focused on objectivity and qualitative data. Research on animal emotions, especially social emotions, and complex reasoning was rejected as inherently flawed by anthropomorphic assumptions. Curiously, zoomorphism, the application of animal motivations to explain human behavior, held some popularity from the 1960s to the 1970s.
As behaviorism receded in psychology, comparative research on cognition, problem-solving, and emotions in animals resumed. While anthropomorphism is still widely considered by many to be invalid scientific reasoning, a minority perspective on the values of anthropomorphism is gaining strength. As a well-regarded primatologist, Frans de Waal, PhD writes in his 1997 article, Are We in Anthropodenial?, “As soon as we admit that animals are far more like our relatives than like machines, then anthropodenial becomes impossible and anthropomorphism becomes inevitable – and scientifically acceptable” (de Waal 1997). However, not all anthropomorphism is useful, as also noted by de Waal. Through hours of observation, a primatologist knows that a seemingly grinning chimpanzee may be aggressive, just as many pet dog owners can differentiate a snarl from human smiling. “A careful observer may thus arrive at an informed anthropomorphism that is at odds with extrapolations from human behavior.”
Anthropocentrism is the tendency to interpret the behaviors, emotions, or cognition of other animals using humans as a reference point. Anthropocentric, meaning human centered, perspectives take on four major forms in comparative psychology. First, studies can directly compare animal cognition, emotion, and behavior to humans. Often humanlike outcomes are considered the standard for success. Traditional anthropocentric ideas used the phylogenetic scale to legitimize their perspective. The phylogenetic scale, or scala naturae, is the notion of a linear ladder of evolution from low-level worms, fish, and reptiles to more complex birds, mammals, and primates. Humans were viewed as the pinnacle of evolution. While terminologies like “higher” and “lower” animals remain, modern conceptualizations of phylogeny see evolution along distinct branches, rather than a linear progression.
Second, researchers can latently interpret behavior as more sophisticated or desirable, when it is merely more humanlike. Ecological and adaptation approaches offer alternatives to these aspects of anthropocentrism. For example, early research on memory examined if animals formed abstract categories, similar to humans. Ecological approaches ask different questions, examining how animals use their memory for tasks such as foraging, traveling long distances, or managing complex social hierarchies.
Third, research designs and research questions can neglect to consider the different sensory experience of animals. Jakob von Uexküll (1957) proposed the idea of “umwelt,” taken from the German word for “environment” or “surrounding world,” to remind researchers to consider the “subjective experiences” of all species and individuals within a species even when they are living in the same environment. When the sensory abilities and perceptions of species other than humans are ignored, the behavioral and social repertoires remain incomplete. For example, many insects perceive ultraviolet waves that emanate from potential food sources or from conspecifics. These abilities were untapped initially because researchers limited their measures to the human visual perception range, forgetting that some species have extrasensory abilities. Infrasonic communication between elephants over long distances (Payne et al. 1986) and ultrasonic communication for some dolphins and whales (e.g., Samarra et al. 2010) were only discovered once equipment with the appropriate measuring range was utilized.
Finally, research in comparative psychology can be considered anthropocentric if its expressed goal is to further the understanding of human psychology. Advocates of comparative psychology suggest that animals should be studied for their own sake rather than to advance the understanding of humans.
Ethology and Tinbergen’s Four Questions
The Dutch ethologist and zoologist Nikolaas Tinbergen was one of the most influential figures in the ethological branch of comparative psychology. He believed that an organism’s behavior can be assessed through complementary perspectives expressed as four questions that he proposed to guide ethological research, two assessing the ultimate causes of behavior (e.g., What is the evolutionary function of this behavior?) and two assessing proximate causes of behavior (e.g., What environment or motivation triggers this behavior?) (Tinbergen 1963).
Questions about ultimate causes of behavior center around the evolution across phylogenetic backgrounds and the adaptive function of a behavior. A researcher who is interested in the phylogeny of a targeted behavior may direct the attention toward the understanding of the patterns of that behavior and may be interested in conducting a cross-species comparison to determine whether the behavior of interest is shared and among which animal species it is shared. A researcher who is interested in the adaptive function of a targeted behavior may want to examine how a targeted behavior is adopted by the animal to efficiently use its external environment, to establish social relationships with its conspecifics, and to successfully reproduce. Phylogeny and adaptive function are the two levels that constituted Tinbergen’s theory of ultimate causes of behavior.
Questions about proximate causes encompass biological causal mechanisms and the development of a specific behavior (ontogeny) (Bateson 2014; Papini 2010). Answers to questions that address phylogeny and adaptation of behaviors do not provide information about the emergence of behavioral skills that are necessary to perform a specific behavior. A researcher who is interested in the mechanism that regulates a behavior may investigate the integration of sensory and motor information, the various functions of the brain and the influence of those functions on behavior, and the external factors that determine the occurrence of a behavior. A researcher who is interested in the development of a particular behavior may explore the influence of age, experience, presence of social partners, type of interaction, observational learning, and other factors that could contribute to changes over time of the behavior under study.
Phylogeny Versus Ecology
To the extent that comparative psychology is facilitated by the comparison of psycho-behavioral phenomena across species, the issue of choosing a comparison species or comparable behaviors remains central dilemmas. Traditional comparative psychology seeks to determine how the mechanisms that guide behavior evolved and how it is distributed across the animal kingdom, Tinbergen’s question of phylogeny. In studying behavior across related species, researchers aim to reconstruct the origin of the behavioral mechanisms and perceptual responses in evolutionary history. Behaviors are considered homologous if they share a similar origin or a common ancestry.
The social ethology (sometimes called socio-ecology) perspective shifts the focus from historical ancestry to the modern ecology of species. Social ethologists see shared environmental pressures as more important to understanding behavior and social structure than evolutionary history. Comparisons based on phylogeny as well as shared ecology are prevalent in modern comparative psychology.
Evolutionary-Developmental Framework: Nature Versus Nurture
Comparative psychology searches for the genesis of behavior, evolutionarily as well as through the developmental lifespan of individuals. Particular emphasis has been placed on early development in an effort to discern innate from learned behavior. Scholars of instincts focus on innate behavioral responses present at infancy, such as imprinting in birds. Ethologists emphasized the role of “nature,” meaning innate instinctual responses. Behaviorists focused on “nurture,” studying infancy and early development as a “blank slate” for learning. During this time, the diversity of species studied by comparative psychologists diminished in favor of a model species approach. Learning was theorized as a universal process following general rules that was relatively invariant across species.
Modern comparative psychologists study both the innate and learned influences of behavior, as well as the complex interplay between the two influences. Comparative psychology studies an ever-increasing number of diverse species and behaviors. Rather than focusing on classifying a behavior dichotomously as innate or learned, comparative psychologists use the onset of a behavior during the developmental process to explain behavioral patterns.
Sharing its name with the discipline, this approach incorporates the comparison of behavior and traits between individuals that share a common ancestry or traits that emerged due to convergent evolution (Hailman 1998). A current example is represented by the work of Elisabetta Palagi and colleagues on the presence and nature of play across a number of mammals (Palagi et al. 2015). Their work has indicated that, in primates, egalitarian species display more social play and tolerance along with a greater use of play signals often expressed in facial expressions (e.g., Ciani et al. 2012; Scopa and Palagi 2016). The comparative approach is also used to examine the behavior and traits of extant species to make generalizations about extinct species (Hailman 1998). Using fossils and contextual clues, paleontologists can draw inferences about prey-predator relationships, physical movement, parental care, foraging habits, or degree of sociality of extinct species. When combined with behavioral and physiological information from currently living descendants, scientists can model various processes by which a particular lineage evolved. The comparative approach addresses questions regarding the relationship between genetics and environment, the pressures that led to changes in ancestral species to the current descendants, and evolved differences in sociality and adaptability to different environments. Comparing across species was the primary method used during the infancy of comparative psychology. However, when the behaviorist approach gained momentum, the comparative method was reduced to a narrow set of species that were easily managed and experimentally manipulated in laboratories (Gariépy 1998). The emergence of ethology encouraged scientists to resurrect the comparative method using more naturalistic contexts and methods (Gariépy 1998).
One of psychology’s traditions is to conduct experimental-based research in which an independent variable is manipulated under controlled circumstances to assess the resulting effects on a dependent variable. While this method allows for causal conclusions, it also limits the generalizability of the findings due to the artificial setting created during experimental conditions. The experimental approach was especially popular during the height of the behaviorists when most of our current knowledge of motivation, classical conditioning, operant conditioning, memory, and other learning phenomena was derived from laboratory-based experiments using a narrow range of species, such as albino rats (Rattus sp.; e.g., Watson, Thorndike), zebrafish (Danio rerio; e.g., Bitterman), and pigeons (Columba sp.; e.g., Skinner, Wasserman). Considered a major limitation by more traditional comparative psychologists and ethologists, the experimental approach was criticized for its narrow scope and limited ability to approximate naturalistic conditions especially with semi-domesticated or laboratory-bred species (reviewed by Beach 1960; Gariépy 1998; Haraway and Maples 1998 ). Despite these limitations, experimental studies were and remain critical in understanding the causal mechanisms of behavior. For example, research conducted on the mating preferences of male and female lizards has tested experimentally a number of mechanism and phylogenetic hypotheses by experimentally manipulating different physical attributes for males and females and testing mate preference (e.g., Keren-Rotem et al. 2016; Sacchi et al. 2015; Swierk et al. 2013). These tests have been conducted both in the field and in the laboratory with wild-caught and bred lizards using both natural variation in live animals and experimentally manipulated models.
In response to the artificial contexts of experimental research, ethologists emphasized the importance of examining behavior within naturalistic settings, arguing that the laboratory setting constrained the production of natural behavior (reviewed by Gariépy 1998; Haraway and Maples 1998). Focused on questions about the function, the development, and the evolution of a given trait or behavior, ethologists approached these questions using closely related species in their natural habitats (Gariépy 1998; Haraway and Maples 1998). Early ethologists primarily used observational techniques to study animals in their natural habitat. Looking for similarities between individuals of a species, ethologists mapped species-typical behavior using very detailed observation notes and behavioral checklists called ethograms in completely uncontrolled environments. Jane Goodall’s work with the chimpanzees of Gombe (Goodall and Pusey 2016) and Dian Fossey’s work with the mountain gorillas of Africa (Fossey 1970) are prime examples of the importance of conducting observational research over long periods of time. A consistent presence in the field allowed the animals to acclimate to their presence and provided both researchers with opportunities to experience and observe behaviors that were unparalleled in laboratory or zoological settings (e.g., holding infants, alliance formation, homosexual behavior). Contemporary ethologists incorporate both observational (paper and electronic behavioral ethograms) and experimental techniques (e.g., playbacks, model simulations, cross-fostering) into studies today to investigate traditional topics of species-typical behavior like courtship, parenting, foraging, and locomotion as well as more psychologically oriented topics, such as empathy, problem-solving, memory, play, and cooperation (e.g., de Waal 2008; Osvath et al. 2014; Plotnik and de Waal 2014).
Extensions of comparative psychology and ethology included E.O. Wilson’s (1929–current) sociobiology, which emphasized the biological basis and evolution of social behavior and ultimately developed into behavioral ecology (e.g., Krebs and Davies 1978) and evolutionary psychology (e.g., Cosmides and Tooby 1987). Behavioral ecology is the scientific study of behaviors that evolved due to ecological pressures (Krebs and Davies 1978) while evolutionary psychology focuses on the adaptiveness of psychological and mental processes displayed by humans and our ancestors as influenced by evolution (e.g., Cosmides and Tooby 1987).
Today, all of these disciplines are actively investigating a diverse set of questions with each discipline focused on a particular aspect of behavior, whether it is problem-solving, cooperation, migration, foraging habits, learning, parenting, aggression, communication, sociality, or mating. Comparative psychology exists in many forms, including behavioral neuroscience, animal science, zoology, behavioral ecology, and ethology to name a few. Each field emphasizes different methodologies including laboratory-based experiments, field-based observations, and naturalistic-based experiments. Some fields focus on specific animal models, while others incorporate more diverse species that systematically vary across phylogenetic background. And, within each field, researchers may focus on proximate questions of ontogeny and mechanism or on ultimate questions of phylogenetic evolution and functional adaptation.
Conclusion: The Future of Comparative Psychology
As discussed here, a clear definition of comparative psychology has been challenging to determine, partly due to the fact that this branch of psychology is one of the oldest fields within the study of psychology (Papini 2010). Since the controversies of the mid 1900s between psychologists and biologists interested in the study of animal behaviors, Tinbergen’s approach (1963) has been the most closely related method used to conduct comparative research. Questions that address how the causes of specific behaviors relate to the phylogeny and adaptive significance of behavior, whereas questions that address how individuals come to adopt different behaviors dependent upon the situation relate to the mechanism and the development of behavior (Tinbergen 1963). Comparative psychology is the discipline which integrates these aspects of behaviors and examines the related questions utilizing the knowledge of psychological theories and the understanding of behavioral neuroscience, developmental biology, behavioral ecology, and evolutionary principles (Papini 2010). The interdisciplinary nature and integrative perspective that distinguish this branch of psychology may be the fundamental reason for recent concerns about the future of comparative psychology as addressed by Abramson (2015). The majority of undergraduate psychology programs in the United States do not include comparative psychology in their academic core classes, and very few of these programs offer an academic course identified as comparative psychology (Abramson 2015). Within the field of psychology, the comparative method has been adopted by the majority of the subfields, such as developmental psychology, cognition, social psychology, and psychology of learning. For both human and nonhuman animal studies, comparative psychology is utilized to compare behaviors across various stages of development, to investigate interspecies differences and commonalities in cognitive abilities, to examine the influence of culture and social environment on an individual’s behaviors, to study behavioral variations dependent upon different life experience. This research approach has extended to various biological sciences, including developmental biology, comparative physiology, comparative anatomy, neuroscience, comparative neurobiology, and animal science, which use the comparative method to approach their questions. Despite the concerns exposed by Abramson (2015), the majority of comparative psychologists, who responded to Abramson’s commentary, agreed that comparative psychology, today, must be seen as a perspective rather than a discipline on its own (Chiandetti and Gerbino 2015; McMillan and Sturdy 2015; Osvath and Persson 2015; Vasconcelos and Pandeirada 2015). It is an interdisciplinary approach that teaches critical thinking skills through cross-discipline training. It is the bridge that brings biological and social sciences together with the goal of providing a more complete knowledge of principles that govern behaviors and developing novel ideas that advance apparently distant research fields.
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