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“Conservations” with a chimpanzee
Abstract
Two chimpanzees (Pan tryglodytes), Fanny and Jane, were presented with liquid and number conservation problems. One chimpanzee, Jane, was successful in solving both sets of problems in that she was not distracted by irrelevant transformations, being influenced only by changes in quantity. Her success appeared to be based on the ability to make inferences rather than on simple perceptual judgement of the final comparison. The results are compared and contrasted with those of Premack, in G. Woodruff, D. Premack, and K. Kennel [(1978). Conservation of liquid and solid quantity by the chimpanzee. Science, 202:99–994] and J. Mehler and T. G. Bever [(1967). Cognitive capacity of very young children. Science, 158:141–142; (1968). Quantification, conservation and nativism. Science, 162:979–981], and it is suggested that there may be a similarity of conservation development between chimpanzees and man.
... However, birds that had experience with visible transformations were not deceived by subsequent invisible transformations and again chose randomly. The birds showed statistically significant contrast between data on visible and invisible transformations but, like Sarah, could not justify their choices, and some critics argue that such random choice results are difficult to interpret (Muncer, 1983). ...
... All other studies, on great apes (chimpanzees, Beran, 2010;Muncer, 1983;Suda & Call, 2004;orangutans, Pongo pygmaeus, Call & Rochat, 1996Suda & Call, 2004; bonobos, Pan paniscus, Suda & Call, 2004), used what is known as "overconservation" (Mehler & Bever, 1967). Overconservation relies on a subject always choosing the larger amount of a desirable liquid; thus, researchers begin with two different amounts, usually in equivalent containers, and then perform various visible and invisible transformations to track the effect of these changes on their subjects' choices. ...
... Overconservation relies on a subject always choosing the larger amount of a desirable liquid; thus, researchers begin with two different amounts, usually in equivalent containers, and then perform various visible and invisible transformations to track the effect of these changes on their subjects' choices. Muncer (1983), for example, used screens to hide the lower half of differently sized destination containers so the resulting quantities would look equivalent. One of his two apes, Jane, understood conservation at some level, failing when she did not view the transformation (i.e., choosing randomly) and succeeding when she did (choosing what was still the larger amount). ...
... However, birds that had experience with visible transformations were not deceived by subsequent invisible transformations and again chose randomly. The birds showed statistically significant contrast between data on visible and invisible transformations but, like Sarah, could not justify their choices, and some critics argue that such random choice results are difficult to interpret (Muncer, 1983). ...
... All other studies, on great apes (chimpanzees, Beran, 2010;Muncer, 1983;Suda & Call, 2004;orangutans, Pongo pygmaeus, Call & Rochat, 1996Suda & Call, 2004; bonobos, Pan paniscus, Suda & Call, 2004), used what is known as "overconservation" (Mehler & Bever, 1967). Overconservation relies on a subject always choosing the larger amount of a desirable liquid; thus, researchers begin with two different amounts, usually in equivalent containers, and then perform various visible and invisible transformations to track the effect of these changes on their subjects' choices. ...
... Overconservation relies on a subject always choosing the larger amount of a desirable liquid; thus, researchers begin with two different amounts, usually in equivalent containers, and then perform various visible and invisible transformations to track the effect of these changes on their subjects' choices. Muncer (1983), for example, used screens to hide the lower half of differently sized destination containers so the resulting quantities would look equivalent. One of his two apes, Jane, understood conservation at some level, failing when she did not view the transformation (i.e., choosing randomly) and succeeding when she did (choosing what was still the larger amount). ...
Piagetian liquid overconservation was investigated in four grey parrots (Psittacus erithacus). Birds tracked the larger of two quantities that had undergone various manipulations. Experiment 1 involved controls to ensure birds could track movement of the quantities, including direct and diagonal cross-transfers. All birds succeeded. In Experiment 2, different amounts in the same transparent or opaque containers were transferred into containers rigged such that amounts then looked equal. All birds chose the larger amounts after transformation when initial cups were transparent, but were random or had consistent side preferences when initial cups were opaque (thus obscuring quantity differences), showing that they used inferential, not perceptual, information, and that no extraneous cues existed. In Experiment 3, two birds saw different amounts from same-sized transparent or opaque containers transferred to containers of different sizes, rigged such that resultant amounts appeared to fill both cups and in which lesser amounts appeared greater on some trials. The older bird demonstrated full use of inferential abilities; he succeeded in all tasks when initial cups were transparent but, again, had consistent side preferences with initially opaque cups. The younger succeeded in the direct transfers with transparent initial cups but was random or showed a side preference on diagonal-transfer tasks and on all the tasks with opaque initial cups. However, she had no preference for the cup that appeared fuller, suggesting she did not use perceptual cues. Overall, grey parrots appear to understand the constancy of liquids undergoing physical transformation. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
... The new presentation style may present the quantity in a manner that makes it appear to be a different amount because of the size and shape of the new container that holds it. Several great ape species including chimpanzees are successful in these paradigms, accurately selecting the larger quantity even after its spatial transformation (e.g., Call and Rochat, 1996; Muncer, 1983; Suda and Call, 2004, 2005; Woodruff et al., 1978). In Experiment 2, we adopted this general approach by first presenting the chimpanzees with sets that were completely intact in their original form. ...
... This differed from Experiment 1 in which the items were broken out of the chimpanzees' view. In previous studies examining the conservation of quantities, great apes have successfully conserved a food set's quantity across manipulations of the set's presentation style, accurately selecting the larger of two quantities even after the set had been spatially transformed (Call and Rochat, 1996; Muncer, 1983; Suda and Call, 2004, 2005; Woodruff et al., 1978). Thus, perhaps the chimpanzees could overcome their current biases against larger quantities of food that consisted of broken items if those sets were first presented in their original state as whole foods. ...
... If the chimpanzees were able to conserve the set's quantitative value following the breaking procedure, they always should have selected the larger of two sets regardless of whether this set was then broken (completely or partially). Despite chimpanzees' proficiency in classic conservation tasks (Muncer, 1983; Suda and Call, 2004, 2005; Woodruff et al., 1978), their current biases against broken items persisted in Experiment 2. We interpret these results as being indicative of a qualitative bias against broken items that were originally whole rather than a failure to discriminate quantities. The chimpanzees were proficient in discriminating the larger of two sets when both sets contained whole items or both sets contained broken items in baseline trials. ...
... The new presentation style may present the quantity in a manner that makes it appear to be a different amount because of the size and shape of the new container that holds it. Several great ape species including chimpanzees are successful in these paradigms, accurately selecting the larger quantity even after its spatial transformation (e.g., Call and Rochat, 1996;Muncer, 1983;Call, 2004, 2005;Woodruff et al., 1978). In Experiment 2, we adopted this general approach by first presenting the chimpanzees with sets that were completely intact in their original form. ...
... This differed from Experiment 1 in which the items were broken out of the chimpanzees' view. In previous studies examining the conservation of quantities, great apes have successfully conserved a food set's quantity across manipulations of the set's presentation style, accurately selecting the larger of two quantities even after the set had been spatially transformed (Call and Rochat, 1996;Muncer, 1983;Call, 2004, 2005;Woodruff et al., 1978). Thus, perhaps the chimpanzees could overcome their current biases against larger quantities of food that consisted of broken items if those sets were first presented in their original state as whole foods. ...
... If the chimpanzees were able to conserve the set's quantitative value following the breaking procedure, they always should have selected the larger of two sets regardless of whether this set was then broken (completely or partially). Despite chimpanzees' proficiency in classic conservation tasks (Muncer, 1983;Call, 2004, 2005;Woodruff et al., 1978), their current biases against broken items persisted in Experiment 2. We interpret these results as being indicative of a qualitative bias against broken items that were originally whole rather than a failure to discriminate quantities. The chimpanzees were proficient in discriminating the larger of two sets when both sets contained whole items or both sets contained broken items in baseline trials. ...
Decision-making largely is influenced by the relative value of choice options, and the value of such options can be determined by a combination of different factors (e.g., the quantity, size, or quality of a stimulus). In this study, we examined the competing influences of quantity (i.e., the number of food items in a set) and quality (i.e., the original state of a food item) of choice items on chimpanzees’ food preferences in a two-option natural choice paradigm. In Experiment 1, chimpanzees chose between sets of food items that were either entirely whole or included items that were broken into pieces before being shown to the chimpanzees. Chimpanzees exhibited a bias for whole food items even when such choice options consisted of a smaller overall quantity of food than the sets containing broken items. In Experiment 2, chimpanzees chose between sets of entirely whole food items and sets of initially whole items that were subsequently broken in view of the chimpanzees just before choice time. Chimpanzees continued to exhibit a bias for sets of whole items. In Experiment 3, chimpanzees chose between sets of new food items that were initially discrete but were subsequently transformed into a larger cohesive unit. Here, chimpanzees were biased to choose the discrete sets that retained their original qualitative state rather than toward the cohesive or clumped sets. These results demonstrate that beyond a food set's quantity (i.e., the value dimension that accounts for maximization in terms of caloric intake), other seemingly non-relevant features (i.e., quality in terms of a set's original state) affect how chimpanzees assign value to their choice options.
... Five studies of conservation in primates have been published. Two (Czerny & Thomas, 1975;Pasnak, 1979) were concerned with the prerequisite skills for conservation, and the three others (Muncer, 1983;Thomas & Peay, 1976;Woodruff, Premack, & Kennel, 1978) directly tested the presence of this operation. Some of these studies have already been reviewed (Dumas & Dore, 1986;Thomas & Walden, 1985); therefore, we summarize their main conclusions. ...
... In the case of this chimpanzee, the exact nature of the inferences remains unknown. Muncer (1983) administered conservation tests with liquid quantity and number to two female chimpanzees and used a method that does not require sameness-difference judgment. On the basis of the idea that a chimpanzee will always pick more food of a favored substance if he or she can discriminate between quantities, Muncer transformed the larger quantity so that it appeared to be the same size as or smaller than the original comparison standard quantity. ...
... Success could not have been achieved by perceptual judgment, and it, thus, seems that the successful subject understood the invariance principle. Muncer (1983) identified, however, two important caveats for his study. First, the overconservation technique may be conceptually easier than the normal conservation paradigm, because it requires only the conservation of the relation of more or less (which is a preoperational skill) rather than the conservation of the relation of equality. ...
During the last 15 years, Piaget's theory and methods have been used to investigate the cognitive capacities and development of nonhuman primates as well as of a few avian and mammalian species. Most studies have focused on formal testing of object permanence, but data are also available on sensory-motor intelligence, on the concepts of space and causality, and on imitation. Some primate studies have tested concrete-operational prerequisites and skills (conservation, classification, and seriation). Methodological flaws and conceptual ambiguities prevent any firm conclusion on the cognitive capacities of some species studied. Reliable data are available on such mammalian carnivores as cats, dogs, and wolves, and various studies confirm the close similarity between ape and human sensory-motor development. There are also indications that great-ape intelligence develops beyond this point, and chimpanzees display basic elements of symbolic representation. The heuristic value and the limits of the Piagetian approach are assessed in terms of its contribution to the analysis of animal cognitive development and to comparative psychology. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
... Finally, Muncer (1983) tested two juvenile chimpanzees on liquid and number conservation. Only 1 subject manifested liquid and number conservation by choosing above chance the largest of two volumes regardless of their perceptual appearance. ...
... The idea of conservation was initially developed in children, yet no direct comparison between human and nonhuman animals (i.e., using the same materials and pro-cedure) has been attempted. Second, although both Woodruff et al. (1978) and Muncer (1983) suggested that inference rather than perceptual estimation was responsible for their subjects' conservation responses, it is not clear whether the inferential strategies used by their subjects entailed the logical necessity described by Piaget and Inhelder (1941). Third, the extent to which this reasoning generalizes across different liquid conservation tasks and across different individuals of the same species is also an open question given that previous studies have used a single task with 1 or 2 subjects only. ...
... Such an interview is obviously not possible with nonhuman primates. The pointing technique used in the present research dictates the use of unequal quantities in the context of "overconservation" tasks (Bryant, 1972;Muncer, 1983). ...
Four orangutans (1 juvenile, 2 subadults, and 1 adult) and ten 6-8-year-old children were tested in 4 liquid conservation tasks of increasing levels of difficulty. Task difficulty depended on the type of transformation (continuous vs. discontinuous quantities) and the relative contrast between the shapes of the containers. Results indicate that orangutans did not display conservation in the strict sense; instead they showed "partial" conservation (intermediate reactions according to J. Piaget & B. Inhelder, 1941). In contrast, some of the children provided evidence of conservation in all 4 tasks, showing "true" or logically necessary conservation in the original sense proposed by J. Piaget and B. Inhelder (1941). Although orangutans did not show conservation in the strict sense, as J. Piaget (1955) and others have generally agreed it should be defined, orangutans behaved as individual and creative problem solvers, adopting different perceptual strategies depending on the task.
... As for the conservation of liquid quantities, chimpanzees, orangutans, and bonobos have been tested in this ability. All of these liquid conservation studies except one applied an "overconservation" procedure in which subjects had to track a larger quantity of juice/syrup (versus a smaller quantity) as it was transformed by being poured into different shaped containers (Call andRochat 1996, 1997;Muncer 1983;Suda and Call 2004). In the remaining study, a languagetrained chimpanzee, Sarah, who had acquired the use of two tokens representing "same" and "different", respectively, judged whether a pair of liquid (or solid) quantities remained equal after one of them had underwent visual transformation (Woodruff et al. 1978). ...
... Overall results of these studies suggested that apes understood to some degree the invariance of liquid quantities because perceptual strategies such as visual estimation alone could not explain their performance. There were three lines of evidence supporting this: (1) apes were moderately successful at making a conservation judgment even when quantities were transferred into opaque containers and thus visual estimation was impossible (orangutans, Call and Rochat 1997;bonobos, chimpanzees, and orangutans, Suda and Call 2004); (2) some individuals needed to see pre-transformation states of quantities in order to make a correct judgment (one chimpanzee, Muncer 1983; one bonobo, one chimpanzee, and three orangutans, Suda and Call 2004; one chimpanzee, Woodruff et al. 1978); (3) two chimpanzees were able to distinguish mere visual transformation from addition and subtraction (Muncer 1983;Woodruff et al. 1978). In contrast, it was also found that apes were not totally free from sometimes misleading perceptual information such as container shape (orangutans, Call andRochat 1996, 1997; bonobos, chimpanzees, and orangutans, Suda and Call 2004). ...
... Overall results of these studies suggested that apes understood to some degree the invariance of liquid quantities because perceptual strategies such as visual estimation alone could not explain their performance. There were three lines of evidence supporting this: (1) apes were moderately successful at making a conservation judgment even when quantities were transferred into opaque containers and thus visual estimation was impossible (orangutans, Call and Rochat 1997;bonobos, chimpanzees, and orangutans, Suda and Call 2004); (2) some individuals needed to see pre-transformation states of quantities in order to make a correct judgment (one chimpanzee, Muncer 1983; one bonobo, one chimpanzee, and three orangutans, Suda and Call 2004; one chimpanzee, Woodruff et al. 1978); (3) two chimpanzees were able to distinguish mere visual transformation from addition and subtraction (Muncer 1983;Woodruff et al. 1978). In contrast, it was also found that apes were not totally free from sometimes misleading perceptual information such as container shape (orangutans, Call andRochat 1996, 1997; bonobos, chimpanzees, and orangutans, Suda and Call 2004). ...
This study investigated whether physical discreteness helps apes to understand the concept of Piagetian conservation (i.e. the invariance of quantities). Subjects were four bonobos, three chimpanzees, and five orangutans. Apes were tested on their ability to conserve discrete/continuous quantities in an over-conservation procedure in which two unequal quantities of edible rewards underwent various transformations in front of subjects. Subjects were examined to determine whether they could track the larger quantity of reward after the transformation. Comparison between the two types of conservation revealed that tests with bonobos supported the discreteness hypothesis. Bonobos, but neither chimpanzees nor orangutans, performed significantly better with discrete quantities than with continuous ones. The results suggest that at least bonobos could benefit from the discreteness of stimuli in their acquisition of conservation skills.
... More recent studies have confirmed and contributed to these findings; chimpanzees are proficient in choosing the larger amount of food across a range of conditions (e.g., Beran 2001Beran , 2004Beran , 2012Beran and Beran, 2004;Boysen and Berntson, 1995;Dooley and Gill, 1977;Hanus and Call, 2007;Rumbaugh et al., 1987). Furthermore, chimpanzees and other great apes also are proficient in conservation tasks (Piaget, 1965) in which they accurately judge quantities when they are spatially transformed into new arrangements (e.g., when liquids are poured into new container shapes and sizes, Muncer, 1983;Call, 2004, 2005;Woodruff et al., 1978). Thus, chimpanzees should easily navigate a task in which two food quantities are presented without any contextual effects that might bias how those quantities are perceived. ...
... It is important to note that the relative fullness of the small cup impacted judgments such that fuller small cups (i.e., those that were completely full or overflowing) led to more choice biases than less-full small cups. Thus, despite high proficiency in relative quantity judgments (e.g., Beran, 2001Beran, , 2004, and evidence of conservation of quantity (e.g., Muncer, 1983;Woodruff et al., 1978), some chimpanzees experienced a 'less-is-better' effect in which smaller 429 or equal quantities were preferred to larger quantities in contexts in which they appeared more full or overflowing. ...
The context in which food is presented can alter quantity judgments leading to sub-optimal choice behavior. Humans often over-estimate food quantity on the basis of how food is presented. Food appears larger if plated on smaller dishes than larger dishes and liquid volumes appear larger in taller cups than shorter cups. Moreover, smaller but fuller containers are preferred in comparison to larger, but less full containers with a truly larger quantity. Here, we assessed whether similar phenomena occur in chimpanzees. Four chimpanzees chose between two amounts of food presented in different sized containers, a large (2 oz.) and small (1 oz.) cup. When different quantities were presented in the same-sized cups or when the small cup contained the larger quantity, chimpanzees were highly accurate in choosing the larger food amount. However, when different-sized cups contained the same amount of food or the smaller cup contained the smaller amount of food (but looked relatively fuller), the chimpanzees often showed a bias to select the smaller but fuller cup. These findings contribute to our understanding of how quantity estimation and portion judgment is impacted by the surrounding context in which it is presented.
... With a different approach, Muncer (1983) attempted to clarify the ability to conserve liquid quantities in chimpanzees. The applied procedure involves unequal quantities instead of equivalent quantities and is called an over-conservation task as opposed to the standard Piagetian conservation task. ...
... Although subjects of the three tested species showed the conflict between an appreciation of the liquid's identity and the reliance on visual information, the orangutans tended to outperform the bonobos and chimpanzees across the experiments, showing a higher tolerance for potentially misleading visual stimuli. This orangutan's superiority is noteworthy because previous studies seemed to indicate that chimpanzees perform better than orangutans (Call & Rochat, 1996;Muncer, 1983;Woodruff et al., 1978). The findings in the OD condition deserve special attention in this regard. ...
An understanding of Piagetian liquid conservation was investigated in 4 bonobos (Pan paniscus), 5 chimpanzees (Pan troglodytes), and 5 orangutans (Pongo pygmaeus). The apes were tested in the ability to track the larger of 2 quantities of juice that had undergone various kinds of transformations. The accuracy of the apes' judgment depended on the shape or number of containers into which the larger quantity was transferred. The apes made their choice mainly on the basis of visual estimation but showed modest success when the quantities were occluded. The results suggest that the apes rely to a greater extent on visual information, although they might have some appreciation of the constancy of liquid quantities.
... In Piaget's classic liquid conservation task originally developed for children (Piaget & Inhelder, 1974), the child watches while liquid is poured from one clear container into another one with a different shape, and the child must state whether the amount of liquid is now the same as before or different. Some apes have passed nonverbal adaptations of such tests (Call & Rochat, 1996, 1997Muncer, 1983;Suda & Call, 2004;Woodruff et al., 1978). In addition, some apes have passed nonverbal appearance-reality tests in which the apparent properties of an object are at odds with its true properties. ...
Psychological essentialism is the ability to recognize that the class or kind to which an object belongs remains unaltered despite changes to its superficial perceptual features. It is unclear whether humans are unique in possessing this ability or whether it is present in nonhuman primates. A recent study with three great ape species found suggestive evidence of psychological essentialism, but further research is needed to rule out the alternative explanation that the apes used locational information to pass the test. We tested a bonobo (Pan paniscus) with specialized symbolic skills, Kanzi, using a modified procedure that avoided this alternative explanation. Kanzi passed the test, which required him to indicate which of two superficially identical but essentially different kinds of items was actually the item requested by the experimenter (e.g., successfully indicating the banana when both items looked like carrots). A control test indicated that he had not passed the essentialism test simply by detecting differences in the superficial appearance of the items. Our findings support the conclusion that great apes are capable of psychological essentialism; however, Kanzi is unique in that he is able to comprehend some simple spoken English and use lexigram symbols to communicate with humans. The extent to which these skills contributed to his essentialism is unknown. Further research designed to specify the limits of essentialism in bonobos, and other great apes, that are not symbol-proficient can inform debates about the phylogenetics of essentialism and the role of language in its development and expression.
... Sarah had previously been trained, via a communication system involving plastic chips, on how to label similarity and difference between two items, and thus could label the sets of liquid as "same" or "different" both before and after various transformations (Woodruff et al., 1978). Muncer (1983) used an overconservation task, a slightly different approach (see Mehler & Bever, 1967;Piaget, 1968), in his studies with two chimpanzees. In an overconservation task, quantities are always different and the subject is expected always to choose the greater amount whatever the transformation. ...
An understanding of Piagetian liquid conservation was investigated in four Grey parrots (Psittacus erithacus), their ages ranging from initially less than 1 year old to 18 years old. They were tested in several conditions: on the ability to choose between (a) identical containers filled with a greater or lesser quantity of a desirable liquid to see if they would reliably take the larger amount and (b) equal quantities of liquid that were visibly or invisibly transferred from identical to different-sized containers to examine their abilities with respect to conservation. Invisible transfers examined the extent to which birds chose based on perceptual evaluations of quantity and the effects of task order on their decisions. Adult birds succeeded on all or most aspects of the tests. As a chick (∼6 months), 1 bird was unable or unwilling to choose between the smaller and larger quantities in the first stage of testing, but upon reaching juvenile status succeeded in all aspects of the tests. Grey parrots thus demonstrate some understanding of liquid conservation. (PsycINFO Database Record
... W. Menzel & Davenport, 1962). In addition, like adult humans, they and other great apes appear to understand conservation of quantity (e.g., Call & Rochat, 1996;Muncer, 1983;Suda & Call, 2004Woodruff, Premack, & Kennel, 1978). However, they also sometimes show biases that are suboptimal to the goal of obtaining the most food. ...
Human cognition affords our species an excellent toolbox for solving problems. Many nonhuman animal species appear to share with humans some of these tools. However, human cognition also is fallible. Susceptibility to perceptual illusions, misrepresentation of probabilities, cognitive biases, faulty memory, and heuristics all present sources of error from which behavior is suboptimal in the pursuit of goals. Some nonhuman species share these perceptual and cognitive biases with humans. Examples of this are described for nonhuman primates, ranging from perceptual illusions to humanlike failures on games of probability such as the Monty Hall Problem. Sometimes the performances of nonhuman primates mirror those of humans, but there are exceptions. Given that other species do experience things erroneously and make errors in judgment, it is an exciting question of whether they also might generate any strategies to offset their fallibility. Two examples to suggest that they do are provided from research with chimpanzees. One is of strategic self-distraction in the face of tempting rewards in a delay of gratification task. The other is of information-seeking behaviors in different contexts where chimpanzees have different types of information. This research, and that of many other groups, shows the value of examining perceptual and cognitive errors across species, and how different individuals and different species may be equipped psychologically to deal with the possibility of these errors occurring.
... Chimpanzees have also been found to be capable of using a scale model of their enclosure as a source of information about where food is hidden in the enclosure, an ability which arguably involves a form of dual representation (Kuhlmeier, Boysen, & Mukobi, 1999). A number of chimpanzees (and other great apes) have also succeeded in Piagetian-style conservation tasks in which, for example, a fixed amount of liquid may appear to increase or decrease when it is transferred into another container (Muncer, 1983;Suda & Call, 2004;Woodruff, Premack, & Kennel, 1978). That these apes were not fooled by the transformation suggested they could be capable of AR discrimination. ...
... Chimpanzees also can discriminate very small differences between quantities of food items (e.g., Menzel 1961;Menzel and Davenport 1962), sometimes even matching or exceeding the performance of human adults in these judgments (e.g., Menzel 1960). And, chimpanzees and other great apes accommodate the effect (or non-effect) of spatially transformed quantities that are moved to new arrangements or poured into different sized containers, thereby showing evidence of quantity conservation (e.g., Call and Rochat 1996;Muncer 1983;Call 2004, 2005;Woodruff et al. 1978). But, they also may experience illusory percepts that constrain accurate representation of quantities and therefore disrupt optimal choice behavior that maximizes intake. ...
We investigated whether chimpanzees (Pan troglodytes) misperceived food portion sizes depending upon the context in which they were presented, something that often affects how much humans serve themselves and subsequently consume. Chimpanzees judged same-sized and smaller food portions to be larger in amount when presented on a small plate compared to an equal or larger food portion presented on a large plate and did so despite clearly being able to tell the difference in portions when plate size was identical. These results are consistent with data from the human literature in which people misperceive food portion sizes as a function of plate size. This misperception is attributed to the Delboeuf illusion which occurs when the size of a central item is misperceived on the basis of its surrounding context. These results demonstrate a cross-species shared visual misperception of portion size that affects choice behavior, here in a nonhuman species for which there is little experience with tests that involve choosing between food amounts on dinnerware. The biases resulting in this form of misperception of food portions appear to have a deep-rooted evolutionary history which we share with, at minimum, our closest living nonhuman relative, the chimpanzee.
... Liquid-conservation tasks, for example, test participants' appreciation of the fact that the quantity of a liquid is unchanged when it is poured from one container into another with different proportions. Apes have enjoyed some success in conservation tasks (Call & Rochat, 1996, 1997Muncer, 1983;Suda & Call, 2004;Woodruff, Premack, & Kennel, 1978), although it is not clear to what extent they used strategies that did not rely upon appearance-reality understanding, such as tracking the larger amount of liquid through the transfer or estimating quantities by visual inspection after the transfer. Thus, investigations aimed more directly at testing apes' appearance-reality understanding are needed. ...
A milestone in human development is coming to recognize that how something looks is not necessarily how it is. We tested appearance-reality understanding in chimpanzees (Pan troglodytes) with a task requiring them to choose between a small grape and a big grape. The apparent relative size of the grapes was reversed using magnifying and minimizing lenses so that the truly bigger grape appeared to be the smaller one. Our Lens test involved a basic component adapted from standard procedures for children, as well as several components designed to rule out alternative explanations. There were large individual differences in performance, with some chimpanzees' responses suggesting they appreciated the appearance-reality distinction. In contrast, all chimpanzees failed a Reverse Contingency control test, indicating that those who passed the Lens test did not do so by learning a simple reverse contingency rule. Four-year-old children given an adapted version of the Lens test failed it while 4.5-year-olds passed. Our study constitutes the first direct investigation of appearance-reality understanding in chimpanzees and the first cross-species comparison of this capacity.
... This species is a New World primate and is valuable to comparative studies because it shares an older common ancestor with humans than do Old World primates such as rhesus macaques and chimpanzees. To date, researchers have shown that capuchins exhibit a similar degree of competency to rhesus macaques and chimpanzees with regard to ordinal judgments of computerized item arrays (Brannon and Terrace 2000; Judge et al. 2005), ordinal judgments of Arabic numerals and tokens (Addessi et al. 2007; Beran et al. 2008a; Tomonaga and Matsuzawa 2000; Washburn and Rumbaugh 1991), and discrete quantity conservation of digital dot arrays (Beran 2007aBeran , 2008 Muncer 1983; Suda and Call 2005). Researchers also have investigated this species' ability to compare discrete quantities of naturally relevant objects and arrays. ...
Recent assessments have shown that capuchin monkeys, like chimpanzees and other Old World primate species, are sensitive to quantitative differences between sets of visible stimuli. In the present study, we examined capuchins' performance in a more sophisticated quantity judgment task that required the ability to form representations of food quantities while viewing the quantities only one piece at a time. In three experiments, we presented monkeys with the choice between two sets of discrete homogeneous food items and allowed the monkeys to consume the set of their choice. In Experiments 1 and 2, monkeys compared an entirely visible food set to a second set, presented item-by-item into an opaque container. All monkeys exhibited high accuracy in choosing the larger set, even when the entirely visible set was presented last, preventing the use of one-to-one item correspondence to compare quantities. In Experiment 3, monkeys compared two sets that were each presented item-by-item into opaque containers, but at different rates to control for temporal cues. Some monkeys performed well in this experiment, though others exhibited near-chance performance, suggesting that this species' ability to form representations of food quantities may be limited compared to previously tested species such as chimpanzees. Overall, these findings support the analog magnitude model of quantity representation as an explanation for capuchin monkeys' quantification of sequentially presented food items.
... ation between the two quantifies (same vs. different) if some of the initial quantifies were added or subtracted. However, the use of same-dn'f" erent tokens did not allow for a specification of which quantity was perceived as the larger and hence did not provide any information regarding the perceptual cues on which the animal based her judgments. Muncer (1983) reported that one of two juvenile chimpanzees demonstrated liquid and number conservation by selecting the larger of two quantities following physical transformations. This chimpanzee persisted in differentiating the larger of two quantities despite changes in perceptual appearance. In a series of experiments, Call and Rochat (1996) rec ...
The perceptual strategies used by 4 orangutans (2 subadults, 2 adults) when choosing the larger of 2 volumes in a Piagetian conservation task were investigated. Three possible perceptual strategies were investigated: (a) direct perceptual estimation of the container's content independent of its shape, (b) use of the spatial and temporal cues provided by the pouring of liquid from one container to another, and (c) ability to initially identify the larger volume and track it across transformations disregarding misleading perceptual cues. Results indicated that the direct perceptual estimation strategy was the best candidate to explain the orangutan's systematic choice of the larger of 2 quantities.
... This procedure arguably induces potential conflict between a notion of identity (i.e. the liquid is the same and hence its quantity should remain unchanged) and appearance (i.e. the liquid looks different after the transformation) (Cantor, 1983). A modified nonverbal version of liquid conservation task, "over-conservation", has been used to test nonhuman great apes (Call & Rochat, 1996, 1997Muncer, 1983;Suda & Call, 2004). The task begins by presenting apes with a pair of identical clear containers filled with different amounts of juice, the larger of which they likely select. ...
The study investigates what an intermediate success rate means in bonobos, chimpanzees, and orangutans. Apes participated in liquid conservation experiments where they had to track the larger of two different quantities of juice after various kinds of transformations [Suda, C., & Call, J. (2004). Piagetian liquid conservation in the great apes (Pan paniscus, Pan troglodytes, and Pongo pygmaeus). Journal of Comparative Psychology, 118, 265-279). When making a decision, apes sometimes demonstrated hesitant behavior, concurrently pointing to both alternatives or successively changing their choice. Moderately successful apes showed more hesitation than highly successful or unsuccessful apes. The results are consistent with the cognitive conflict model: The experiments created a higher degree of cognitive conflict on moderately successful apes than on very successful or unsuccessful apes. This indicates that an intermediate performance reflects the joint operation and potential conflict between two different cognitive strategies (identity and appearance) inherent to the Piagetian conservation task.
The perceptual strategies used by 4 orangutans (2 subadults, 2 adults) when choosing the larger of 2 volumes in a Piagetian conservation task were investigated. Three possible perceptual strategies were investigated: (a) direct perceptual estimation of the container's content independent of its shape, (b) use of the spatial and temporal cues provided by the pouring of liquid from one container to another, and (c) ability to initially identify the larger volume and track it across transformations disregarding misleading perceptual cues. Results indicated that the direct perceptual estimation strategy was the best candidate to explain the orangutan's systematic choice of the larger of 2 quantities.
This chapter reviews recent scientific evidence legitimizing animal mathematics. In particular, numerous cognitive and neurological studies suggest that animals mathematize like humans. Such findings trouble the common belief by many in mathematics education that mathematics is a uniquely human enterprise. I conclude by suggesting possible benefits animal-mathematics studies may hold for the work of mathematics education.
We made an observational study of spontaneous imitation in orangutans (Pongo pygmaeus). Previous studies may have underestimated great apes' imitative capacities by studying subjects under inhibiting conditions- We used subjects living in enriched environments, namely, rehabilitation. We collected a sample of spontaneous imitations and analyzed the most complex incidents for the likelihood that true imitation, learning new actions by observing rather than by doing, was involved in their acquisition. From 395 hr of observation and other reports on 26 orangutans, we identified 354 incidents of imitation. Of these, 54 complex incidents were difficult to explain by forms of imitation based on associative processes grounded in experiential learning alone; they were, however, congruent with acquisition processes that include true imitation. These findings suggest that orangutans may be capable of true imitation and point to critical eliciting factors.
Major directions of studies on the complex behavioral forms in anthropoid apes are presented, such as tool-using activity, language learning with the aid of gestures and signs symbolizing words, comparison and generalization of signals by relative and identical features, discrimination of quantitative features of the signals, social behavior, etc. It follows from the review of literature that the interest in the problem of evolution of the intellect as well as of the zoosocial intragroup relations in anthropoids does not decrease. Meanwhile, this problem remains not only actual but also one of the most complicated ones. The most interesting and the least studied seems to be the investigation of various forms of social behavior and formation of intellectual capabilities in ontogenesis of chimpanzees.
We made an observational study of spontaneous imitation in orangutans (Pongo pygmaeus). Previous studies may have underestimated great apes' imitative capacities by studying subjects under inhibiting conditions. We used subjects living in enriched environments, namely, rehabilitation. We collected a sample of spontaneous imitations and analyzed the most complex incidents for the likelihood that true imitation, learning new actions by observing rather than by doing, was involved in their acquisition. From 395 hr of observation and other reports on 26 orangutans, we identified 354 incidents of imitation. Of these, 54 complex incidents were difficult to explain by forms of imitation based on associative processes grounded in experiential learning alone; they were, however, congruent with acquisition processes that include true imitation. These findings suggest that orangutans may be capable of true imitation and point to critical eliciting factors.
Although many studies have shown that nonhuman animals can choose the larger of two discrete quantities of items, less emphasis has been given to discrimination of continuous quantity. These studies are necessary to discern the similarities and differences in discrimination performance as a function of the type of quantities that are compared. Chimpanzees made judgments between continuous quantities (liquids) in a series of three experiments. In the first experiment, chimpanzees first chose between two clear containers holding differing amounts of juice. Next, they watched as two liquid quantities were dispensed from opaque syringes held above opaque containers. In the second experiment, one liquid amount was presented by pouring it into an opaque container from an opaque syringe, whereas the other quantity was visible the entire time in a clear container. In the third experiment, the heights at which the opaque syringes were held above opaque containers differed for each set, so that sometimes sets with smaller amounts of juice were dropped from a greater height, providing a possible visual illusion as to the total amount. Chimpanzees succeeded in all tasks and showed many similarities in their continuous quantity estimation to how they performed previously in similar tasks with discrete quantities (for example, performance was constrained by the ratio between sets). Chimpanzees could compare visible sets to nonvisible sets, and they were not distracted by perceptual illusions created through various presentation styles that were not relevant to the actual amount of juice dispensed. This performance demonstrated a similarity in the quantitative discrimination skills of chimpanzees for continuous quantities that matches that previously shown for discrete quantities.
A review of selected aspects of cognitive performance in apes and in monkeys suggests that only rarely can we at this time demonstrate greater cognitive competence in the ape than in the monkey. Instead it seems that the ape's cognitive style differs qualitatively from that of the monkey: not in the direction of greater capacity (using this term as a measure of continuously increasing ability), but in the way that the ape applies itself to a novel situation. From this it would follow that the greater discontinuity lies between man and apes, not between apes and monkeys.
We made an observational study of spontaneous imitation in orangutans (Pongo pygmaeus). Previous studies may have underestimated great apes' imitative capacities by studying subjects under inhibiting conditions. We used subjects living in enriched environments, namely, rehabilitation. We collected a sample of spontaneous imitations and analyzed the most complex incidents for the likelihood that true imitation, learning new actions by observing rather than by doing, was involved in their acquisition. From 395 hr of observation and other reports on 26 orangutans, we identified 354 incidents of imitation. Of these, 54 complex incidents were difficult to explain by forms of imitation based on associative processes grounded in experimental learning alone; they were, however, congruent with acquisition processes that include true imitation. These findings suggest that orangutans may be capable of true imitation and point to critical eliciting factors.
The relationship between age, relative numerousness judgment, and summation was investigated in 11 Western lowland gorillas (Gorilla gorilla gorilla). Experiments 1 and 2 evaluated the gorillas' ability to select the larger of 2 food quantities before and with training. The majority of gorillas did not reliably select the larger quantity in Experiment 1 until receiving training to do so in Experiment 2. Experiment 3 evaluated their ability to select the larger of 2 pairs of quantities. All gorillas selected the larger pair more often than chance, and the old were less accurate and slower than were the young. For most gorillas, performance in relative numerousness judgment with training and summation was comparable with previous reports in chimpanzees and orangutans.
Conservation of quantity occurs through recognition that changes in the physical arrangement of a set of items do not change the quantity of items in that set. Rhesus monkeys (Macaca mulatta) were presented with a computerized quantity judgment task. Monkeys were rewarded for selecting the greater quantity of items in one of two horizontal arrays of items on the screen. On some trials, after a correct selection, no reward was given but one of the arrays was manipulated. In some cases, this manipulation involved moving items closer together or farther apart to change the physical arrangement of the array without changing the quantity of items in the array. In other cases, additional items were added to the initially smaller array so that it became quantitatively larger. Monkeys then made another selection from the two rows of items. Monkeys were sensitive to these manipulations, changing their selections when the number of items in the rows changed but not when the arrangement only was changed. Therefore, monkeys responded on the basis of the quantity of items, and they were not distracted by non-quantitative manipulations of the sets.
The ability to select the larger of two quantities ranging from 1 to 5 (relative numerousness judgment [RNJ[) and the ability to select the larger of two pairs of quantities with each pair ranging from 1 to 8 (summation) were evaluated in young, middle-aged, and older adult orangutans (7 Pongo pygmaeus abelii and 2 Pongo pygmaeus pygmaeus). Summation accuracy and RNJ were similar to those of previous reports in apes; however, the pattern of age-related differences with regard to these tasks was different from that previously reported in gorillas. Older orangutans were less accurate than the young and middle-aged for RNJ, and summation accuracy was equivalent among age groups. Evidence was found to suggest that the young and middle-aged based their selection of the largest quantity pair on both quantities within each pair during the summation task. These results show a relationship between subject age and the quantitative abilities of adult orangutans.
Nonhuman animals demonstrate a number of impressive quantitative skills such as counting sets of items, comparing sets on the basis of the number of items or amount of material, and even responding to simple arithmetic manipulations. In this experiment, capuchin monkeys were presented with a computerized task designed to assess conservation of discrete quantity. Monkeys first were trained to select from two horizontal arrays of stimuli the one with the larger number of items. On some trials, after a correct selection there was no feedback but instead an additional manipulation of one of those arrays. In some cases, this manipulation involved moving items closer together or farther apart to change the physical arrangement of the array but not the quantity of items in the array. In other cases, additional items were added to the initially smaller array so that it became quantitatively larger. Monkeys then made a second selection from the two arrays of items. Previous research had shown that rhesus monkeys (Macaca mulatta) succeeded with this task. However, there was no condition in that study in which items were added to the smaller array without increasing its quantity to a point where it became the new larger array. This new condition was added in the present experiment. Capuchin monkeys were sensitive to all of these manipulations, changing their selections when the manipulations changed which array contained the larger number of items but not when the manipulations changed the physical arrangement of items or increased the quantity in one array without also reversing which of the two arrays had more items. Therefore, capuchin monkeys responded on the basis of the quantity of items, and they were not distracted by non-quantitative manipulations of the arrays. The data indicate that capuchins are sensitive to simply arithmetic manipulations that involve addition of items to arrays and also that they can conserve quantity.
Reviews studies which attempt to reduce linguistic or other performance demands in the assessment of Piagetian concepts. It is argued that a precise diagnosis of cognitive skills is important for several reasons: for testing claims concerning the sequencing or concurrence of cognitive acquisitions, for assessing the effects of training or educational interventions, and for evaluating models of underlying process. In many of the studies reviewed, performance on the revised test proved no better than on standard Piagetian tests, and in many others a high level of performance was rendered suspect by methodological problems. Some studies, however, provided suggestive (although seldom conclusive) evidence that an understanding of concepts such as conservation and transitivity might emerge earlier than Piaget indicated. The point is stressed that nonverbal assessment is not inherently opposed to Piagetian theory. It is suggested that the effect of nonverbal studies may be to provide a firmer basis for the claim of nonlinguistic operational structures. (85 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Conducted 3 conservation experiments with a total of 164 3-6 yr. olds to determine whether young children understand the invariance of quantity. Results show that (a) even 3-yr-olds were able to transfer a quantity judgment over a perceptual transformation very well, (b) Ss only failed to make this kind of transfer when the judgments normally produced by the pre- and post-transformation displays were in direct conflict, and (c) training that some cues provide a more reliable basis for quantity judgments than others enabled Ss to transfer quantity judgments over perceptual transformations much more effectively than they had previously. It is concluded that very young children have a basic understanding of invariance, and that their real difficulty in quantity tasks is in distinguishing between a correct and an incorrect basis for quantity judgments. (French summary) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
The rationale was to apply Piaget’s theory and methods to the study of the phylogenetic development of cognitive abilities.
It was asked whether squirrel monkeys have the prerequisite skills for conservation of quantity, and, specifically, whether
they might respond differentially to equivalent and unequivalent volumetric cues. All monkeys responded significantly and
differentially to pairs of identical objects or pairs of objects similar only in volume vs. pairs of objects which differed
in volume. It was concluded that squirrel monkeys have the prerequisite skills for the conservation of quantity. Discussion
included methodological problems associated with demonstrating conservation in nonhumans as well as the potential usefulness
of Piaget’s theory for phylogenetic studies of intelligence.
New studies support the hypothesis that young children have basic cognitive capacities but utilize them inefficiently; older
children aid these capacities with generally valid cognitive heuristics which produce poor performance on critical problems.
Children between 2 years, 6 months old and 3 years, 2 months old correctly discriminate the relative number of objects in
two rows; between 3 years, 2 months and 4 years, 6 months they indicate a longer row with fewer objects to have "more"; after
4 years, 6 months they again discriminate correctly. The discriminative ability of the younger children shows that the logical
capacity for cognitive operations exists earlier than previously acknowledged.
8 Chimpanzees, 4 orangutans, 4 gibbons and 4 rhesus were given a choice between a standard invisible size of banana (i.e., covered by an opaque plaque) and a variable visible size of banana. All groups showed an approximate 2% "bird-in-hand" constant error, preferring the visible, but groups differed in accuracy of food size selection (difference threshold SDs). Chimpanzees interchangeably used visible foods or differentially colored plaques as cues to the larger of 2 rewards, used any 2 visible foods or signs of foods, as a cue to a 3rd (invisible) food size, and "rank ordered" 5 plaques by brightness, etc., for the sole reward of securing 5 hidden foods in order by size.
Approaching intelligence as a biological phenomenon, the author has developed some unique and perhaps controversial, theories about the nature of intelligence, based on the evolution of the 400 million year record of the brain cavities of vertebrate fossils. The book presents the full scope of the organic evolution of the vertebrate brain, beginning with the earliest endocasts from late Silurian and early Devonian times, up to the evolution of the hominids and, most recently, modern man about 250,000 yr ago. The author examines such things as the trend towards an increase in relative brain size and its relevancy to intelligence as an evolving behavioral capacity; the evolution of cognitive capacities for representing reality, which is treated as a necessary consequence of neural organization; and the selection pressures associated with the major evolutionary transitions (from water to land, to the air, to nocturnal and fossorial niches, and finally to the elaborate social worlds,) delineating their significance to the brain's development.
Every aspect of an organism’s behavior bears the indelible imprint of the biological operating principles of its own species. Whatever a cat does, it does in a feline fashion; whatever man does, he does in a human fashion. This may be taken as an axiom (or truism, for that matter, for how could it be otherwise?). An animal cannot change its constitution between behaviors; every movement, every sensation, every insight, every motive is mediated, coordinated, regulated, transformed, integrated, etc., by one and the same nervous system, the same skeleton, the same irritable tissues. Despite the infinite variability in individual acts or skills (many of them dependent upon environmental circumstances), there remain limits to the behavioral variations, and there are physiological constants that are common to literally everything a given animal does. I would like to propose, as a general guidline for research in animal behavior, that one can gain important insights into the biological nature of a species by attempting to discover the physiological constants—by searching for the common denominators underlying the different sorts of behavior in an animal’s repertoire.
During the first 18 months of life, gorilla and human infants follow much the same course of psychological development, but the nonhumans embark on this sooner, and generally finish sooner. Exceptions to this arise in areas of reciprocal and constructive play with objects, for here, the human subjects excelled and the gorillas appeared to be uninterested.
An effort is made to show that every conservation problem assesses 2 forms of conservation-identity and equivalence-and that Piaget's theory of conservation is a theory of the conservation of identity and not of equivalence. Misunderstandings of Piaget's position on conservation are attributed to his failure to make clear the distinction between the 2 forms of conservation, and his tendency to interpret conservation problems as assessments of the conservation of identity when, in fact, equivalence is the only form of conservation directly assessed by the standard conservation task.
A summary of the growth of logical operational thinking in the child, with emphasis on the concrete operations of class inclusion and serialization. Harvard Book List (edited) 1971 #605 (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Reviews a study of cognitive capacities of young children, 21/2 yr. and older, made by J. Mehler and T. G. Bever (see record
1968-00570-001). Additional experimental data were obtained as part of an evaluation of conclusions reached concerning the development of quantitative concepts. 29 2.3-3.1 yr. olds were interviewed with Mehler and Bever's displays of "2 rows of 4 or 6 elements in optical correspondence." It is concluded that the Mehler and Bever argument for an "innate structure" is superfluous and not justified, and that "innate functioning is sufficient." (PsycINFO Database Record (c) 2012 APA, all rights reserved)
The experiment was conducted in two sessions over two successive days on 90 children with a mean age of 5-1. All Ss were given pretests and posttests of conservation of number, length, and substance. Half were given pretraining on the verbal discrimination of length and number, and half were not. One-third of the Ss in each of the pretraining groups were given direct training on number conservation, one-third were exposed to situations designed to produce "internal cognitive conflict," and one-third received no training on number conservation. Subjects in the conflict-plus-verbal pretraining group outperformed Ss in the control group without verbal pretraining. There was very little transfer of training from number conservation to other kinds of conservation.
A chimpanzee used word order correctly when assessed for production and comprehension of unfamiliar sequences of three signs expressing actual relationships based on the prepositions “behind” and “in”. She also learnt to comprehend “and”, “or” and “not”, but failed to perform according to usage in human languages when “and” and “or” were negated.RésuméUn chimpanzé femelle utilisait correctement l'ordre des mots dans la production et la compréhension de séquences non familiéres de 3 signes experimant des relations réelles fondées sur les prépositions “derrière” et “dans”. Elle apprit aussi à comprendre “et”, “ou” et “pas” mais elle échouait lorsque l'ordre comportait la négation de “et” ou de “pas”.ZusammenfassungEin Schimpanse war imstande, die Wortordnung korrekt anzuwenden, ween sie für die Produktion und das Verständnis unbekannter Folgen von drei Zeichen geprüft wurde, die aktuelle Beziehungen ausdrücken, basierend auf den Präpositionen “hinter” und “in”. Der Affe lernte auch “und”, “oder” und “nicht” zu verstehen, aber war nicht in der Lage, sich entsprechend dem Gebrauch der menschlichen Sprache zu verhalten, wenn “und” und “oder” verneint wurden.
Sarah, an adult "language"-trained chimpanzee, made accurate same-different judgments on quantities of liquid and solid matter and conserved both types of quantity despite a transformation in an irrelevant property (shape). Control tests showed that she judged on the basis of inference rather than perceptual evaluation of the quantities. She failed to make accurate same-different judgments on the basis of number, and she was not tested for conservation of this type of quantity.
The sensorimotor period in monkeys. Colloquium presented at Columbia Uni- What children do in spite of what they know
- M Antonucci
- T G Bever
- J Mehler
- J Epstein
Antonucci, M. (1980). The sensorimotor period in monkeys. Colloquium presented at Columbia Uni-Bever, T. G., Mehler, J., and Epstein, J. (1968). What children do in spite of what they know. Science, Piaget, J. (1968).
The sensorimotor period in monkeys. Colloquium presented at Columbia University
- M Antonucci
Progress in Ape Research
- G. B. Dooley
- T. V. Gill
Behaviour of Non-Human Primates
- K. J. Hayes
- C. J. Nissen
Psychology and the Handicapped Child
- E. H. Lenneberg
- B. S. Long
- Elkind
- Gruen
Quantification, conservation and nativism
- Mehler J.
Piaget's sensorimotor series in an infant macaque; The organization of non-stereotyped behavior
- S Parker