Comparative cognition

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Comparative cognition is the comparative study of the mechanisms and origins of cognition in various species, and is sometimes seen as more general than, or similar to, comparative psychology. [1] From a biological point of view, work is being done on the brains of fruit flies that should yield techniques precise enough to allow an understanding of the workings of the human brain on a scale appreciative of individual groups of neurons rather than the more regional scale previously used. [2] Similarly, gene activity in the human brain is better understood through examination of the brains of mice by the Seattle-based Allen Institute for Brain Science (see link below), yielding the freely available Allen Brain Atlas. [3] This type of study is related to comparative cognition, but better classified as one of comparative genomics. Increasing emphasis in psychology and ethology on the biological aspects of perception and behavior is bridging the gap between genomics and behavioral analysis.

Contents

In order for scientists to better understand cognitive function across a broad range of species they can systematically compare cognitive abilities between closely and distantly related species [4] Through this process they can determine what kinds of selection pressure has led to different cognitive abilities across a broad range of animals. For example, it has been hypothesized that there is convergent evolution of the higher cognitive functions of corvids and apes, possibly due to both being omnivorous, visual animals that live in social groups. [4] The development of comparative cognition has been ongoing for decades, including contributions from many researchers worldwide. Additionally, there are several key species used as model organisms in the study of comparative cognition.

Methodology

The aspects of animals which can reasonably be compared across species depend on the species of comparison, whether that be human to animal comparisons or comparisons between animals of varying species but near identical anatomies without a common ancestor. This comparison of cognitive trends can be observed in species across vast distances which feature similar biological features. Gross anatomical study as well as natural variation have been long considered aspects of comparative cognition.

Neurobiology

Current biological anthropology suggests that similarities in structures in the brain can, to an extent, be compared with certain aspects of behavior as their roots. However, it is difficult to quantify exactly which neuron connections are required for advanced function as opposed to basic reactionary cognitive operations, as identified in small insects or other small-brained organisms. [5] Regardless, circuitry common to a wide quantity of organisms has been identified, suggesting a convergence at least of the evolution of common neural Behavioral plasticity which allow for common functions and trends of inherited behavior. [6] It is possible that this is due to the size of the brain having direct correlation to the degree of function. However, it has been noted by experiments carried out on insects by Martin Giurfa in 2015, namely observing honey bees and fruit flies, which suggests that structures in the brain, regardless of size, can relate to functions and explain behavioral skills far greater than gross size can: [7]

As in larger brains, two basic neural architectural principles of many invertebrate brains are the existence of specialized brain structures and circuits, which refer to specific sensory domains, and of higher-order integration centres, in which information pertaining to these different domains converges and is integrated, thus allowing cross-talking and information transfer. These characteristics may allow positive transfer from a set of stimulus to novel ones, even if these belong to different sensory modalities. This principle appears crucial for certain tasks such as rule learning.

To this end, recent years have instead dedicated entirely to mapping signals and pathways of the brain in order to compare across species as opposed to using brain size. Further studies in this field are ongoing, especially as the process of tracking and stimulating neuron development changes.

Key contributors

Charles Darwin

Darwin initially suggested that humans and animals have similar psychological abilities in his 1871 publication The Descent of Man and Selection in Relation to Sex, where he stated that animals also present behaviors associated with memory, emotion, and desires. [8] To Darwin, humans and animals shared the same mental cognition to varying degrees based on their place in the evolutionary timeline. This understanding of mental continuity between animals and humans form the basis of comparative cognition. [9]

Conwy Lloyd Morgan

In his 1894 publication An Introduction to Comparative Psychology, Morgan first postulated what would become known as Morgan's Cannon, which states that the behaviors of animals cannot be attributed to complex mechanisms when simpler mechanisms are possible. [10] Morgan's cannon criticized the work of his predecessors for being anecdotal and anthropomorphic, and proposed that certain intellectual animal behavior is more likely to have developed through multiple cycles of trial and error rather than spontaneously through some existing intelligence. [11] Morgan proposed that animals are capable of learning and their observed behavior is not purely the result of instinct or intrinsic mental function.

Edward J. Thorndike

E.J Thorndike measured mental capacity as an organism's ability to form associations between their actions and the consequences of said actions. [10] In his 1898 publication Animal Intelligence: An Experimental Study of Associative Processes in Animals, Thorndike outlined his famous "puzzle box" experiments. Thorndike placed kittens inside a specialized box which contained a lever or button which, when triggered by the cat, would allow the cat to escape. Initially, the cats placed within the box would instinctively attempt to escape by randomly scratching the sides of the box. On some instances the cat would hit the lever, allowing their release. The next time this cat was placed within the box, it was able to conduct this trial and error routine again, however they were able to find the lever and release themselves more rapidly. Over multiple trials, all other behaviors that did not contribute to the cat's release were abandoned, and the cat was able to trigger the lever without error. [12] Thorndike's observations explored the extent to which animal's were capable of forming associations and learning from previous experiences, and he concluded that the animal cognition is homologous to the human cognition. [12] Thorndike's experiment established the field of comparative cognition and an experimental science and not simply a conceptual thought. [11] The progressive decrease in escape time observed by Thorndike's cats lead to his development of the Law of Effect, which states that actions and behaviors conducted by the organism which result in a benefit to the organism are more likely to be repeated. [10]

Graph demonstrating the decreasing of response time observed in Thorndike's "puzzle-box" experiments Puzzle box.jpg
Graph demonstrating the decreasing of response time observed in Thorndike's "puzzle-box" experiments

Ivan Pavlov

During his studies of digestive secretions in dogs, Pavlov recognized that the animals would begin to salivate as if in response to the presence of food, even when food has yet to be presented. He observed that the dogs has begun to associate the presence of the assistant carrying the food bowls with receiving food, and would salivate regardless of whether the food bowls would be given to them for feeding. He observed that the dogs has begun to associate the presence of the assistant carrying the food bowls with receiving food, and would salivate regardless of whether the food bowls would be given to them for feeding. Through this observation, Pavlov postulated that it may be possible to create novel response arcs, in which a previously neutral stimulus can be associated with an unconditioned stimulus, and will then trigger a similar or identical response as the initial response to the unconditioned stimulus. [10] The development of this response to a previously unknown stimuli became known as classical conditioning, and established that animal behavior is affected by the environmental conditions. [13]

Burrhus Frederic Skinner

In his 1938 publication The Behavior of Organisms , B.F. Skinner coined the term operant conditioning to refer to the modification or development of specific voluntary behavior through the use of reinforcement and punishment. Reinforcement describes a stimulus which strengthens the likelihood of a behavior being repeated, while punishment describes a stimulus which weakens the likelihood of a behavior being repeated. Skinner designed his operant conditioning chamber, or "Skinner box", and used it to test the effects of reinforcement and punishment on voluntary behaviors.  B.F. Skinner's observations extended the understanding of the Law of Effect presented by Thorndike to include the conditioning of responses through negative stimuli. Similar to Thorndike's "puzzle-box", Skinner's experiments demonstrated that when a voluntary behavior is met with a benefit, such as food, the behavior is more likely to be repeated. Skinner also demonstrated that when a voluntary behavior is met with a punishments', such as an electric shock, the behavior is less likely to be repeated.

Skinner further expanded his experiments to include negative and positive reinforcements and punishments. Positive reinforcements and punishments' involve the introduction of a positive stimulus or a negative stimulus respectively. Negative reinforcements and punishments involve the removal of negative stimulus or a positive stimulus respectively.

Apparatus of the operant conditioning chamber, or "Skinner box", as designed by B.F. Skinner Skinera kaste.png
Apparatus of the operant conditioning chamber, or "Skinner box", as designed by B.F. Skinner

Wolfgang Kohler

Kohler criticized the work of Thorndike and Pavlov for emphasizing the mechanical approach to behavior while ignoring the cognitive approach. He opposed the suggestion that animals learn by simple trial and error, rather they learned through perception and insight. Kohler argued that Thorndike's puzzle-boxes presented no other method of escape except the method presented by the experiment as "correct", and in doing-so the cognitive problem solving abilities of the animal are rendered useless. He suggested that if the subjects were able to observe the apparatus itself, they would be able to deduce methods of escape by perceiving the situation and the environment. Kohler's views were influenced by the observations he made when studying the behaviors of chimpanzees in Tenerife, Spain. Kohler noted that the primates were capable of insight, utilizing various familiar objects from their environment to solve complex problems, such as utilizing tools to reach out of reach items. [10]

Karl Von Frisch

Bee "waggle dance" indicating direction and distance of nearby food source, as observed by Karl von Frisch Bee dance.svg
Bee "waggle dance" indicating direction and distance of nearby food source, as observed by Karl von Frisch

Karl von Frisch studied the "waggle dances" of bee populations. When foraging bees returned to the hive from a food source, they would perform complex, figure eight patterns. Through these observations, von Frisch established that bees were not only capable of recalling spatial memories, but were also able to communicate these memories to other members of the species symbolically. His research also established that other bees were capable of interpreting the information and apply it to their environment and behaviors. [14]

Allen and Beatrix Gardner

The Gardners are famously known for their raising of Washoe the chimpanzee, and their teaching of American Sign Language to Washoe. Researchers have long questioned whether primates, the evolutionary cousins of humans, could be taught to communicate through human speech. While communication through verbal language is not possible, it was hypothesized that sign language could be utilized. The Gardners designed a specialized method which they referred to as cross-fostering, in which they raised Washoe from infancy in a human cultural and social environment, allowing for a comparative analysis of language acquisition in human children and primates. After 51 months of teaching, the Gardners reported that Washoe has 132 signs. [15] Through the methods of the Gardners, Washoe was able to learn to communicate in American sign language, and demonstrated the ability to create novel signs for new factors introduced to her environment. In one instance, Washoe described a Brazil nut, an object whose name she was not familiar with, by signing "rock" and "berry", and continued to refer to the Brazil nut in this way. Washoe also learned how to communicate new information to her handlers. For example, after being asked what was wrong, Washoe was able to indicate a feeling of sickness by signing "hurt" near her stomach. It was later shown that she had contracted an intestinal flu. [16] In another, Washoe had lost a toy and successfully told her handlers of its location and asked for them to retrieve it for her. [15] The Gardners' studies proved that primates are capable of language acquisition, as well as language development and expression of private information through the use of a language similar to human communication.

Model organisms

Canines

Famously used in Ivan Pavlov's classical conditioning experiments, members of the canine family have long been considered a primary model organism for comparative cognition studies. Many other psychologists have utilized canines in their studies. C.L. Morgan referred to his terrier Tony when developing his Cannon, [10] and Thorndike recreated his puzzle-box experiments with dogs as well. Members of this family have been domesticated for much of human history, and in many instances the behaviors of humans have co-evolved alongside these domesticated dogs. It has been hypothesized that this evolutionary relationship between humans and dogs has contributed to the development of complex cognitive behaviors that can be used to study the unique cognitive abilities of canines. [17]

Felines

As another historical companion to humans, felines have co-evolved along with the human species. Use of felines in the study of comparative cognition is most associated with the work of Thorndike and his puzzle-boxes. [12]

Rodents

Rodents such as various species of rats have been used in the experiments of B.F Skinner, as well as others studying comparative cognition, due to the abundance of cognitive similarity between rodents and humans. It has been shown that rodents, specifically rats, and humans present similar memorization and mnemonic processes, as both humans and rodents display primacy and recency effects when tasked with the recollection of numbered items. There is also evidence to support that both rats and humans share similar attentional processes, as they are both able to demonstrate sustained, selective and divided attention. [18]

Corvids

Tool use observed in New Caledonian crows

Corvids have received a lot of attention from the comparative cognition community in the twenty-first century, specifically the species of corvids known as New Caledonian crows. Several populations of this species, located on islands in the New Caledonian archipelago have demonstrated the ability to create and utilize tools to manipulate their environment for their benefit. These crows were observed to modify the ribs of palm leaves by nibbling the ends to resemble a hook, and proceeded to use these tools to reach prey and food in previously inaccessible areas, such as small cracks within trees. It has also been observed that this technique of creating tools has been passed onto future generations [13]

See also

Related Research Articles

<span class="mw-page-title-main">Cognitive science</span> Interdisciplinary scientific study of cognitive processes

Cognitive science is the interdisciplinary, scientific study of the mind and its processes. It examines the nature, the tasks, and the functions of cognition. Mental faculties of concern to cognitive scientists include language, perception, memory, attention, reasoning, and emotion; to understand these faculties, cognitive scientists borrow from fields such as linguistics, psychology, artificial intelligence, philosophy, neuroscience, and anthropology. The typical analysis of cognitive science spans many levels of organization, from learning and decision to logic and planning; from neural circuitry to modular brain organization. One of the fundamental concepts of cognitive science is that "thinking can best be understood in terms of representational structures in the mind and computational procedures that operate on those structures."

<span class="mw-page-title-main">Edward Thorndike</span> American psychologist (1874–1949)

Edward Lee Thorndike was an American psychologist who spent nearly his entire career at Teachers College, Columbia University. His work on comparative psychology and the learning process led to the theory of connectionism and helped lay the scientific foundation for educational psychology. He also worked on solving industrial problems, such as employee exams and testing.

Operant conditioning, also called instrumental conditioning, is a learning process where voluntary behaviors are modified by association with the addition of reward or aversive stimuli. The frequency or duration of the behavior may increase through reinforcement or decrease through punishment or extinction.

<span class="mw-page-title-main">Operant conditioning chamber</span> Laboratory apparatus used to study animal behavior

An operant conditioning chamber is a laboratory apparatus used to study animal behavior. The operant conditioning chamber was created by B. F. Skinner while he was a graduate student at Harvard University. The chamber can be used to study both operant conditioning and classical conditioning.

The experimental analysis of behavior is a science that studies the behavior of individuals across a variety of species. A key early scientist was B. F. Skinner who discovered operant behavior, reinforcers, secondary reinforcers, contingencies of reinforcement, stimulus control, shaping, intermittent schedules, discrimination, and generalization. A central method was the examination of functional relations between environment and behavior, as opposed to hypothetico-deductive learning theory that had grown up in the comparative psychology of the 1920–1950 period. Skinner's approach was characterized by observation of measurable behavior which could be predicted and controlled. It owed its early success to the effectiveness of Skinner's procedures of operant conditioning, both in the laboratory and in behavior therapy.

Comparative psychology is the scientific study of the behavior and mental processes of non-human animals, especially as these relate to the phylogenetic history, adaptive significance, and development of behavior. The phrase comparative psychology may be employed in a narrow and a broad meaning. In its narrow meaning, it refers to the study of the similarities and differences in the psychology and behavior of different species. In a broader meaning, comparative psychology includes comparisons between different biological and socio-cultural groups, such as species, sexes, developmental stages, ages, and ethnicities. Research in this area addresses many different issues, uses many different methods and explores the behavior of many different species from insects to primates.

<span class="mw-page-title-main">Animal cognition</span> Intelligence of non-human animals

Animal cognition encompasses the mental capacities of non-human animals including insect cognition. The study of animal conditioning and learning used in this field was developed from comparative psychology. It has also been strongly influenced by research in ethology, behavioral ecology, and evolutionary psychology; the alternative name cognitive ethology is sometimes used. Many behaviors associated with the term animal intelligence are also subsumed within animal cognition.

Behaviorism is a systematic approach to understand the behavior of humans and other animals. It assumes that behavior is either a reflex evoked by the pairing of certain antecedent stimuli in the environment, or a consequence of that individual's history, including especially reinforcement and punishment contingencies, together with the individual's current motivational state and controlling stimuli. Although behaviorists generally accept the important role of heredity in determining behavior, they focus primarily on environmental events. The cognitive revolution of the late 20th century largely replaced behaviorism as an explanatory theory with cognitive psychology, which unlike behaviorism examines internal mental states.

Habituation is a form of non-associative learning in which a non-reinforced response to a stimulus decreases after repeated or prolonged presentations of that stimulus. For example, organisms may habituate to repeated sudden loud noises when they learn these have no consequences.

<span class="mw-page-title-main">Great ape language</span> Efforts to teach non-human primates to communicate with humans

Research into great ape language has involved teaching chimpanzees, bonobos, gorillas and orangutans to communicate with humans and each other using sign language, physical tokens, lexigrams, and imitative human speech. Some primatologists argue that the use of these communication methods indicate primate "language" ability, though this depends on one's definition of language. The cognitive tradeoff hypothesis suggests that human language skills evolved at the expense of the short-term and working memory capabilities observed in other hominids.

Dog intelligence or dog cognition is the process in dogs of acquiring information and conceptual skills, and storing them in memory, retrieving, combining and comparing them, and using them in new situations.

The law of effect, or Thorndike's law, is a psychology principle advanced by Edward Thorndike in 1898 on the matter of behavioral conditioning which states that "responses that produce a satisfying effect in a particular situation become more likely to occur again in that situation, and responses that produce a discomforting effect become less likely to occur again in that situation."

<span class="mw-page-title-main">Emotion in animals</span> Research into similarities between non-human and human emotions

Emotion is defined as any mental experience with high intensity and high hedonic content. The existence and nature of emotions in non-human animals are believed to be correlated with those of humans and to have evolved from the same mechanisms. Charles Darwin was one of the first scientists to write about the subject, and his observational approach has since developed into a more robust, hypothesis-driven, scientific approach. Cognitive bias tests and learned helplessness models have shown feelings of optimism and pessimism in a wide range of species, including rats, dogs, cats, rhesus macaques, sheep, chicks, starlings, pigs, and honeybees. Jaak Panksepp played a large role in the study of animal emotion, basing his research on the neurological aspect. Mentioning seven core emotional feelings reflected through a variety of neuro-dynamic limbic emotional action systems, including seeking, fear, rage, lust, care, panic and play. Through brain stimulation and pharmacological challenges, such emotional responses can be effectively monitored.

Cat intelligence is the capacity of the domesticated cat to solve problems and adapt to its environment. Research has shown that feline intelligence includes the ability to acquire new behavior that applies knowledge to new situations, communicating needs and desires within a social group and responding to training cues.

<span class="mw-page-title-main">Elephant cognition</span> Intelligence and awareness in elephants

Elephant cognition is animal cognition as present in elephants. Most contemporary ethologists view the elephant as one of the world's most intelligent animals. With a mass of just over 5 kg (11 lb), an elephant's brain has more mass than that of any other land animal, and although the largest whales have body masses twenty times those of a typical elephant, a whale's brain is barely twice the mass of an elephant's brain. In addition, elephants have around 257 billion neurons. Elephant brains are similar to those of humans and many other mammals in terms of general connectivity and functional areas, with several unique structural differences. Although initially estimated to have as many neurons as a human brain, the elephant's brain has about three times the amount of neurons as a human brain. However, the elephant's cerebral cortex has about one-third of the number of neurons as a human's cerebral cortex.

<span class="mw-page-title-main">Animal consciousness</span> Quality or state of self-awareness within an animal

Animal consciousness, or animal awareness, is the quality or state of self-awareness within an animal, or of being aware of an external object or something within itself. In humans, consciousness has been defined as: sentience, awareness, subjectivity, qualia, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind. Despite the difficulty in definition, many philosophers believe there is a broadly shared underlying intuition about what consciousness is.

Discrimination learning is defined in psychology as the ability to respond differently to different stimuli. This type of learning is used in studies regarding operant and classical conditioning. Operant conditioning involves the modification of a behavior by means of reinforcement or punishment. In this way, a discriminative stimulus will act as an indicator to when a behavior will persist and when it will not. Classical conditioning involves learning through association when two stimuli are paired together repeatedly. This conditioning demonstrates discrimination through specific micro-instances of reinforcement and non-reinforcement. This phenomenon is considered to be more advanced than learning styles such as generalization and yet simultaneously acts as a basic unit to learning as a whole. The complex and fundamental nature of discrimination learning allows for psychologists and researchers to perform more in-depth research that supports psychological advancements. Research on the basic principles underlying this learning style has their roots in neuropsychology sub-processes.

Psychological behaviorism is a form of behaviorism—a major theory within psychology which holds that generally human behaviors are learned—proposed by Arthur W. Staats. The theory is constructed to advance from basic animal learning principles to deal with all types of human behavior, including personality, culture, and human evolution. Behaviorism was first developed by John B. Watson (1912), who coined the term "behaviorism", and then B. F. Skinner who developed what is known as "radical behaviorism". Watson and Skinner rejected the idea that psychological data could be obtained through introspection or by an attempt to describe consciousness; all psychological data, in their view, was to be derived from the observation of outward behavior. The strategy of these behaviorists was that the animal learning principles should then be used to explain human behavior. Thus, their behaviorisms were based upon research with animals.

The evolution of cognition is the process by which life on Earth has gone from organisms with little to no cognitive function to a greatly varying display of cognitive function that we see in organisms today. Animal cognition is largely studied by observing behavior, which makes studying extinct species difficult. The definition of cognition varies by discipline; psychologists tend define cognition by human behaviors, while ethologists have widely varying definitions. Ethological definitions of cognition range from only considering cognition in animals to be behaviors exhibited in humans, while others consider anything action involving a nervous system to be cognitive.


Human contingency learning (HCL) is the observation that people tend to acquire knowledge based on whichever outcome has the highest probability of occurring from particular stimuli. In other words, individuals gather associations between a certain behaviour and a specific consequence. It is a form of learning for many organisms.

References

  1. ↑ Beran, Michael J.; Parrish, Audrey E.; Perdue, Bonnie M.; Washburn, David A. (2014-01-01). "Comparative Cognition: Past, Present, and Future". International Journal of Comparative Psychology. 27 (1): 3–30. doi:10.46867/ijcp.2014.27.01.07. ISSN   0889-3667. PMC   4239033 . PMID   25419047.
  2. ↑ Greenspan, Ralph J.; van Swinderen, Bruno (December 2004). "Cognitive consonance: complex brain functions in the fruit fly and its relatives". Trends in Neurosciences. 27 (12): 707–711. doi:10.1016/j.tins.2004.10.002. ISSN   0166-2236. PMID   15541510. S2CID   15780859.
  3. ↑ "Brain Map - brain-map.org". portal.brain-map.org. Retrieved 2021-09-24.
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  5. ↑ Chittka, Lars; Niven, Jeremy (2009-11-17). "Are bigger brains better?". Current Biology. 19 (21): R995–R1008. Bibcode:2009CBio...19.R995C. doi: 10.1016/j.cub.2009.08.023 . ISSN   1879-0445. PMID   19922859. S2CID   7247082.
  6. ↑ Chittka, Lars; Rossiter, Stephen J.; Skorupski, Peter; Fernando, Chrisantha (2012). "What is comparable in comparative cognition?". Philosophical Transactions: Biological Sciences. 367 (1603): 2677–2685. doi:10.1098/rstb.2012.0215. ISSN   0962-8436. JSTOR   41739990. PMC   3427551 . PMID   22927566.
  7. ↑ Giurfa, Martin (2015-03-21). "Learning and cognition in insects". Wiley Interdisciplinary Reviews: Cognitive Science. 6 (4): 383–395. doi:10.1002/wcs.1348. ISSN   1939-5078. PMID   26263427.
  8. ↑ Shettleworth, S.J. (529–546). Darwin, Tinbergen, and the evolution of comparative cognition. New York, NY: Oxford University Press.
  9. ↑ Wasserman, E.A. (1993). "Comparative Cognition: Beginning the second century of the study of animal intellegence". Psychology Bulletin. 113 (2): 211–228. doi:10.1037/0033-2909.113.2.211.
  10. 1 2 3 4 5 6 Roitblat, Herbert L. (1987). Introduction to Comparative Cognition. New York, NY: W.H. Freeman and Company.
  11. 1 2 Olmstead; Kuhlmier, Mary; Valerie (2015). Comparative Cognition. Cambridge, U.K.: Cambridge University Press.{{cite book}}: CS1 maint: multiple names: authors list (link)
  12. 1 2 3 Thorndike, Edward J. (1898). "Animal Intelligence: An experimental study of associative processes in animals". The Psychological Review: Series of Monograph Supplements. 2 (4).
  13. 1 2 Shuttleworth, Sara J. Fundamentals of Comparative Cognition. New York, N.Y.: Oxford University Press.
  14. ↑ Menzel, R. (2019). "The Waggle Dance as an Intended Flight: A Cognitive Perspective". Insects. 10 (12): 424. doi: 10.3390/insects10120424 . PMC   6955924 . PMID   31775270.
  15. 1 2 White Miles, H.L. (1991). "Book Review: Teaching Sign Language to Chimpanzees". International Journal of Primatology. 12 (3): 303–307. doi:10.1007/BF02547591. S2CID   37680550.
  16. ↑ Fouts, Roger S., Mellgren, Roger R. (1976). "Language, signs, and cognition in the chimpanzee". Sign Language Studies. 13: 319–346. doi:10.1353/sls.1976.0004. S2CID   144586199.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  17. ↑ Feuerbacher, Erica N., Wynne, C.D.L. (2011). "A History of Dogs as Subjects in North American Experimental Psychological Research". Comparative Cognition & Behavior Reviews. 6: 46–71. doi: 10.3819/ccbr.2011.60001 . hdl: 10919/81791 .{{cite journal}}: CS1 maint: multiple names: authors list (link)
  18. ↑ Steckler, T., Muir, J.L. (1995). "Measurement of cognitive function: relating rodent performance with human minds". Cognitive Brain Research. 3 (3–4): 299–308. doi:10.1016/0926-6410(96)00015-8. PMID   8806031.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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