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CHAPTER Comparative Evolutionary 2 9 : A United Discipline for the Study of Evolved Traits

Jennifer Vonk and Todd K. Shackelford

Abstract Several themes have emerged from the chapters in this volume. Some tensions exist between researchers seeking to answer questions concerning the adaptive purpose of human and nonhuman behaviors and capacities, and researchers seeking to shed light on the evolutionary forces giving rise to such traits. These tensions may be dissipated if several unnecessary dichotomies are avoided and researchers thereby embraced nonmutually exclusive stances to diff erent methodological and theoretical approaches. We suggest that those studying humans and/or nonhumans—whether in the fi eld or in the lab, with large numbers of participants or with few, from a behaviorist or nativist standpoint, asking questions about structure or function, stressing continuity or discontinuity—focus less on absolutes and existing dogma, and more on openness and objectivity. We suggest that, if all researchers with similar goals unite under the single unifying framework of evolutionary theory, many more advances can be made and a more focused fi eld of study will emerge. Key Words: evolutionary framework, dichotomy, unifying, tensions

Psychology has lagged behind the other natural models of the human with the goal of dissect- sciences, which operate under a single unifying ing human with Wundt’s voluntarism theoretical framework. Physicists accept the laws (Schultz & Schultz, 2008). Titchener’s structuralism of quantum fi eld theory and Einstein’s theory of was similarly focused and restrictive, disavowing relativity without much question. Chemists have the study of the mentally ill, human children, and universally adopted the basic table of elements nonhumans. Th e goal was to discover universal laws and atomic theory. Biologists unequivocally accept of human behavior similar to those that applied in evolutionary theory as, rather than a theory, an all- chemistry and physics and other “hard sciences.” encompassing explanation for the physiological and By viewing man as a machine, given life by a great behavioral adaptations of all life on earth. Psycholo- creator, at the time could hope to uncover gists, in contrast, have seen schools of thought come basic rules and operations by reducing man to his and go in the discipline’s relatively short history, simplest elements; thus, they focused on physiology without a single theoretical viewpoint dominating and anatomy in an attempt to understand the mind. for any signifi cant length of time. With the rise of functionalism through the inspi- Psychology divorced itself from philosophy rational work of , Francis Galton, by virtue of its focus on empirical methods, but , and others, appreci- also immediately adopted a focus on mechanistic ated the utility of more diverse methodology and

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topics of study (Schultz & Schultz, 2008). Darwin’s studies that make comparisons between nonhuman emphasis on mental and physical cross-species and human behavior or cognitive processes, or only continuity also reawakened interest in the study those that situate any organism’s evolved capacities of nonhuman behavior. Psychologists could move within the context of its social and physical environ- away from defi ning the elements of behavior and ment? We have opted for the latter focus. In what consciousness to attempting to explain the purpose follows, we identify some challenges and goals that, and function of behavior. Watson’s when met, will allow current and future scholars to provided the objectivity that was needed to study break new ground in unprecedented directions and other organisms while adhering to rigorous scien- provide the impetus for forging new collaborations tifi c methods by eschewing reference to internal that should produce further insights into the evolu- mental states that could only be inferred. Although tion of not only human psychology and behavior, behaviorism held sway for decades in the United but also the psychology and behavior of our closest States, other movements such as the gestalt move- and more distantly related animal relatives. ment, which retained an emphasis on conscious- First, the divisions that have existed on a number ness, maintained prominence in Europe during of fronts need to be disassembled. Some of these the same time period (Schultz & Schultz, 2008). divisions exist between: (1) researchers who work Watson’s (1914) and Th orndike’s (1911) reduction- primarily with humans and those who work pri- ist approaches to the study of animal mental life marily with nonhumans, (2) fi eld and laboratory have been critiqued for disavowing the principles researchers, (3) behaviorists and nativists or cogni- of (Tolman, 1987). Although evolution- tivists, (4) the idiographic or “small-n” and the nor- ary psychology has continued to exist as a discipline mative approach, and still (5) at some level between within psychology, evolution by natural selection the functionalist and the structuralist approach, but has not achieved the status of an overarching frame- perhaps most critically, (6) anthropocentric and work with which we study all human mental life, “holy-grail” type pursuits and other more objective in the same manner that it exists within biology approaches. for the study of animal behavior and morphology Traditionally, comparative psychologists have (Barkow, Cosmides & Tooby, 1992). Various other focused on nonhuman species in an attempt to shed paradigms have continued to infl uence the method- light on human evolution, but relatively fewer stud- ology, topics of study, and theoretical frameworks ied how human participants performed in analo- of psychology. Although an evolutionary framework gous tests. However, this selectivity is dissipating, may never reach an all-encompassing status within with more comparative psychologists including psychology as a whole, this may be more likely human participants in their experiments (see chap- within the study of animal behavior, or within the ters 6, 14, 15, 20–25 of this volume). Sometimes subfi eld now known as comparative psychology. presenting human participants with the same tests In the introductory chapter to this volume, we that have been presented to our animal counterparts indicated that comparative psychology has some- has provided startling results. For instance, Silva and times lost its focus. Although it is the case that most colleagues (Silva, Page, & Silva, 2005) discovered comparative psychologists accept the principles of that humans fall prey to several of the same irra- evolutionary theory, they remain divided on a num- tional perseverative strategies in the trap-tube prob- ber of other key fronts, some of which are clear when lem as did the chimpanzee subjects in the Povinelli reading the chapters in this volume. We believe that (2003) studies. In the original trap-tube problem, merging the fi elds of comparative psychology and monkeys had to insert one tool into a narrow tube can provide that focus and to push out a food reward, but there was a trap in move the new discipline of comparative evolution- the middle of the tube that caught the food if the ary psychology forward (see also Lockard, 1971). It animals attempted to push the food past the trap was a diffi cult task simply coming up with an appro- (Visalberghi & Limongelli, 1994). If they inserted priate title for this chapter. What should we label the tool from the far side of the tube, over the trap the study area of this new combined discipline? We and out the other end, they could succeed in obtain- could not restrict the focus of study to animal behav- ing the reward. However, if the trap is on top of the ior; would that restrict us from focusing on cogni- tube, it is causally irrelevant. Povinelli’s chimpanzees tive processes or the study of animal ? And we learned to use a rule, “Always insert the tool in the would not want to imply that humans should not be end of the tube farthest away from the trap,” which included within our focus. Should the focus be on they continued to use even when the trap was not

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functional and was at the top of the tube, instead of to use as a guide to develop hypotheses and meth- at the bottom of the tube, indicating that they did ods and strategies for testing those hypotheses. not understand the causal function of the trap. Silva Only when evidence has supported or dispelled and colleagues discovered that humans, surprisingly, these hypotheses can we begin to assume to write often used the same strategy, even though it served or speak with any certainty on whatever issue comes no causal purpose. Humans also avoided the side of to bear. Experimental results and interpretations a table with an ineff ective trap in a trap table version of such should also be questioned until alternative of the problem. In a diff erent paradigm, Horner and explanations for results have been exhaustively ruled Whiten (2005) discovered that children are more out and replications have been conducted. An alter- likely to copy causally irrelevant actions, compared native viewpoint is that basic assumptions should be to chimpanzees, who are more likely to emulate accepted as facts until such time as they are proven rather than imitate. Inoue and Matsuzawa (2007) to be otherwise—but then where is the motive or found that chimpanzees sometimes performed more impetus to test or challenge widely accepted notions, quickly and accurately in a memory task for sequen- some of which become dogma and halt the progress tial order of diff erent numerosities compared to col- of science? For instance, it was a long-held belief, lege students. As Lyn reviews (chapter 19), the well in part due to Darwin’s variability hypothesis, that known bonobo, Kanzi, outperformed human chil- men were intellectually superior to women. Had dren on certain measures of language (understand- Th ompson-Woolley (Th ompson, 1903) and Stetter- ing of embedded clauses) in one of tests (Savage Hollingworth (Hollingworth, 1914), among oth- Rumbaugh et al., 1993). Herbranson & Shroeder ers, not challenged and empirically tested such (2010) found that, even after extensive training, beliefs, other women, like themselves, may not be humans still failed to maximize choices in the well- contributing to the sciences today because they known Monty Hall dilemma, whereas pigeons would not have been provided such opportunities. learned to adjust shift-and-stay strategies to maxi- One need only look at the list of contributors to this mize their rewards, leading the authors to ponder if volume to consider the losses to our own discipline pigeons were “smarter than mathematicians.” In the if women were restricted from contributing to aca- current volume, researchers have explored whether demic pursuits because such a notion was accepted human children are indeed prosocial (chapter 20), without challenge. although interestingly, humans have not been It was also long thought that evolution took place tested in paradigms equivalent to those presented to very slowly, over hundreds of thousands of years. A their nonhuman counterparts. Results with study based on the work of Peter and Rosemary human children have been somewhat mixed, with Grant and their assistants (Weiner, 1994) with the children not always exhibiting prosocial tendencies famous fi nches on the Galapagos Islands, indicat- as expected (Brownell, Svetlova & Nichols, 2009; ing that patterns of drought and rainstorm over a chapter 20). In some cases, human children may, few generations could alter the survival rates and in fact, behave more spitefully than chimpanzees selection pressures on beak size and strength, altered (chapter 20; Jensen, Hare, Call & Tomasello, 2006), that belief. As a more recent example, Subiaul has although one might have predicted the opposite challenged long-held models of , both by prior to having conducted the tests. In addition, showing that monkeys, not just apes, can imitate, more distantly related are more likely to and that imitation may be diff erentiated by type: give food in food-sharing tests of prosocial behav- motor, cognitive, spatial, and so on (chapter 25). ior, compared to our closest living relatives (chapter Science marches forward when investigators move 20). Th us, testing nonhumans, both closely and dis- against the current and have the courage to chal- tantly related species, and humans in conceptually lenge ideas currently “in vogue.” Th eories stagnate identical tasks is far more illuminating than making when they are no longer pitted against new ideas. assumptions about how humans and other species Th erefore, we should not accept ideas that have not would perform in yet untested paradigms. been subjected to careful and rigorous testing, even Th is point returns us to a point raised in the if these are the most popular ideas at the time. opening chapter about where the burden of proof Popular ideas become particularly diffi cult to dis- should lie. Assumptions should always be tested pel because they are more prevalent; the more you before they are accepted as truths; to do otherwise see something the more credible it becomes. Th e is to fail to adhere to the principles of the scientifi c more articles are published that express a particular method. No theory is truth; it is only a framework viewpoint, the more diffi cult it becomes to publish

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an opposing view, because it may be considered too on the other hand in Animal Behaviour (Dorey, Udell far in opposition to the prevailing corpus of data. & Wynne, 2010; Hare et al., 2010; Udell, Dorey & Scientists build careers based on compiling data Wynne, 2008; Wynne, Udell & Lord; 2008), regard- that supports theories they have developed. Th ey ing the role of ontogeny versus in may be reluctant to publish fi ndings that dispute domestic dogs’ response to human pointing their own theories and have now gained signifi cant gestures (Hare, Brown, Williamson & Tomasello, authority and power to suppress others who ques- 2002). (See Miklosi and Topal, chapter 11, for an tion their own views and fi ndings. Results that are extensive exposition of these issues). Other examples in line with the currently “popular” point of view abound in the literature on great ape causal under- is easier to publish, making it increasingly diffi cult standing and theory of mind (Tomasello, Call, & to publish data that challenges such notions, even Hare, 2003a, b; Povinelli & Vonk, 2003, 2004). For if the studies have been conducted with appropri- instance, Povinelli, Nelson, and Boysen (1992) fi rst ate rigor. Although the scientifi c process is objective published results that they interpreted as suggestive and fair over the long run, one need only think back that chimpanzees understood the intentions of oth- to the monopoly that behaviorism held over psy- ers because they quickly learned to switch roles in chology with John Watson as the editor of Journal of a task in which they were allowed to observe and during the early twentieth then both roles. However, after a commentary century to recognize that the scientifi c process can by Heyes (1993), and a re-analysis of the results, it be unfair in the short run. One can see the chang- was suggested that the chimpanzees did not demon- ing trends in the types of articles that are published strate understanding on the fi rst trial of the original depending on the theoretical preference of the most reversal, but instead learned rapidly once the roles successful researchers in the fi eld. A review of ape had been reversed, demonstrating not evidence for language research is one powerful example of chang- “empathy,” as the original article suggested, but ing views in our fi eld (Lyn, chapter 19; see also instead evidence of rapid (Heyes, 1994; Cartmill & Maestripieri, chapter 10). Not so long Povinelli, 1994). A similar argument can be made ago, it was diffi cult to publish articles suggesting that for recent results reported by Manrique, Gross, and even nonhuman primates had elements of theory of Call (2010) who report that great apes select tools mind. It was next to impossible to publish articles on the basis of an understanding of rigidity, a physi- suggesting that more distantly removed animals cal property of objects that might play a causal role might share some components of the human theory in performing certain tasks. However, when exam- of mind system. During the time when behaviorism ining the results of a critical third experiment, one held sway, topics such as theory of mind and meta- can interpret the results as indicating that the apes cognition would not have been extensively studied, have simply learned to choose rigid tools in earlier much less found their way into the fi eld’s top jour- experiments because they are more familiar and nals. Today, fi nding evidence for mental state attri- have been associated with success, and initially do bution in other species seems to be “in vogue” and it not reverse their choices to more pliable tools when is “unpopular” to challenge such notions (de Waal, it becomes causally important to do so, based on 2009; Tomasello, Call & Hare, 2003b). It should a causal understanding of what works in diff erent go without saying that we should maintain objec- situations. Interestingly, while Manrique and col- tivity in our tests. Bias can be a problem in research leagues (2010) generally present a balanced discus- in all areas. It is particularly problematic in com- sion and openly admit that most of the tools readily parative research, somewhat ironically, because we available to their apes are of rigid construction, must infer what the behaviors of our subjects tell us thus potentially biasing them to choose such tools about their mental states. Furthermore, perhaps due in their experiments, they still conclude that chim- to conservation issues and the prevailing notion that panzees “spontaneously” select tools on the basis animals are of more value if they are more similar to of rigidity after “gathering minimal observational humans, some researchers seem invested in specifi c information” (from abstract). Even more revealing, patterns of results—those that support ideas of con- investigators from the same laboratory, also follow- tinuity between humans and other animals. ing a series of tool-related studies with great apes, It is relatively easy to interpret the same pattern conclude that: of results in diff erent ways. Just one example can be seen in the recent exchange between Hare and col- Although our results show that apes succeeded leagues on the one hand and Wynne and colleagues in some problems spontaneously, their group

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performance never exceeded 70% in the initial processes such as metacognition and planning for six trials. It is true that with additional trials the future. Barrett (chapter 2) points out that label- performance increased, but it still remained quite low ing the behavior (i.e., as planning) does nothing in most conditions. One possible explanation for this with regard to explaining it. Perhaps such diff er- outcome is that their performance is not based on ences of opinion cannot easily be resolved. What is causal knowledge about the task. Another possibility important is that both explanations are considered is that they possess some causal knowledge, but equally in all accounts. Equal consideration is most that certain task features make it hard to express it likely to happen when researchers are open to view- consistently. points from those approaching fi ndings from alter- (Herrmann, Wobber, & Call, 2008, p. 229) native perspectives and approaches. However, this openness does not always occur. In other words, the performance of the apes was Such biases lead us to the discrepancy between not consistent with the authors’ preferred explana- the “Holy Grail” approach and what we suggest tion, but they have chosen to maintain that pref- are more objective approaches to the study of both erence anyway. Although researchers are burdened human and nonhuman psychology and behavior. As with the task of acknowledging alternative interpre- was pointed out earlier, sometimes assumptions are tations of our fi ndings, we cannot stop there. We made about how humans will perform in various must also choose to support the conclusion that tasks that are not upheld when the requisite experi- is most consistent with the results, or continue to ments are conducted. We should not be willing test the hypotheses that result. Otherwise we are to ascribe abilities to humans without the appro- doing the scientifi c process a disservice. Th is pro- priate tests to confi rm such ascriptions any more cess is particularly important in a fi eld in which than we should ascribe or fail to ascribe abilities to behaviors are observed but internal processes must nonhumans without the appropriate objective tests be inferred. Smith and colleagues (chapter 15) pres- and interpretations of those data. We should also ent a rigorous review of the research on metacogni- consider that nonhumans may have evolved dif- tion, discussing how fi ndings have been interpreted ferent capacities from those of humans for solving as resulting from learned associations rather than similar problems. Raby and Clayton (chapter 12) from “higher order” cognitive processes such as take pains to defi ne episodic memory and discuss metamemory or conscious planning, and the various whether there might be precursors in nonhumans, ways in which researchers have ingeniously tried to even if the fully developed autonoetic conscious tease apart these explanations, controlling for meth- component that exists in humans is not fully pres- odological confounds and implementing ever more ent in nonhumans who maintain some aspects of creative and sophisticated experimental designs. episodic-like memory. Th ese authors also refl ect on Shettleworth also cautions us to consider how learn- why only some aspects would evolve in these spe- ing, rather than insight or inference, can account for cies, and why a fully developed episodic memory similar patterns of results, sometimes highly touted would emerge in humans. As Feeney and Roberts as evidence for traits previously deemed only within point out (chapter 13), we may fail to fi nd evidence the reach of humans (chapter 28). How researchers for “mental time travel” in nonhumans if we are interpret their results may say more about biases in seeking evidence for only human traits when non- terms of whether they are seeking evidence for con- humans may have evolved their own mechanisms tinuity or discontinuity, rather than whether such for keeping track of past events—mechanisms that continuity or discontinuity exists. are best suited for the ecological niches in which A few of the authors in this volume cite the they have evolved. Shettleworth (chapter 28) makes example given by Osvath (2009) of a chimpanzee a similar point when she argues that it is unlikely in Furuvik Zoo in Sweden, who stashes stones in that nonhumans would have evolved episodic his enclosure for use later as weapons with which to memory to refl ect back on their conscious experi- hurl at zoo visitors. Osvath used the example as evi- ences to tell stories and reminisce, but instead may dence of planning. Feeney and Roberts (chapter 13) have evolved such an ability to make predictions and Raby and Clayton (chapter 12) fi nd this anec- about future events, such as the likelihood of fi nd- dote compelling evidence of such, but Shettleworth ing food or mates. Smith et al. (chapter 15) caution (chapter 28) remains unconvinced and believes the us against treating capacities such as metacognition anecdote can be explained by an associative learn- as all-or-none capacities. Th is tendency might result ing account, without an appeal to higher order in excluding a priori certain taxonomic groups from

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further study. For example, in light of research fi nd- description does not require that the dog infers your ings such as the null results in Gallup’s self-recogni- thoughts, or even his own desires, but rather simply tion tests for monkeys, making the assumption that the causal relationship between your behaviors and monkeys lacking self-recognition would also lack the dog’s behaviors. Th e fi rst explanation may seem metacognition, would have precluded the possibil- more parsimonious, or “simpler,” but it requires an ity of ever fi nding intriguing suggestive evidence additional cognitive step: the dog must infer men- for uncertainty monitoring in old world monkeys. tal states based on behaviors at a causal level, even We must consider that cognitive abilities, such as if these can be skipped over at the level of verbal metacognition, theory of mind, and many others, explanation (see Povinelli & Vonk, 2004). Th us, the might emerge in a manner more akin to a mosaic, former explanation, while linguistically more parsi- rather than as modules. We certainly should not monious, is cognitively more sophisticated. Barrett restrict our studies on the basis of a priori untested presents another example (chapter 2) in which the assumptions. Although we cannot prevent ourselves authors confuse an argument that is easier for their from entering our tests with certain hypotheses, we intended audience to understand with an argument should be willing and open to all possible outcomes that is simpler from the standpoint of parsimony. and ensure that we are interpreting the data in light Morgan himself cautioned that “…surely the sim- of all readings of the data, not just the reading that plicity of an explanation is no criterion of its truth” is most consistent with our preferred outlook, or (Morgan, 1894, p. 54). our own anthropocentric points of view. As scien- Th us, it is easy to see how the rule of parsimony tists, we should not have “preferred” hypotheses. or Occam’s razor can be confused with Morgan’s Our only preference should be for the hypothesis canon. Morgan’s canon posits that, “In no case is that is most consistent with the pattern of data. an animal activity to be interpreted in terms of Researchers have often cited Morgan’s canon higher psychological processes, if it can be fairly (Morgan, 1894) in such discussions, or the rule of interpreted in terms of processes which stand lower parsimony, which have often been confused with in the scale of psychological evolution and develop- each other (see also chapter 2 of this volume). ment” (Morgan, 1903, p. 59). So here the distinc- Whereas the rule of parsimony is often expressed tion is clear; Morgan’s canon refers to the level of as the idea that the simplest explanation is often explanation. Simplicity here refers to the degree of the correct one, and often treated as synonymous cognitive sophistication of the process required to with Occam’s (or Ockam’s) razor (Karin-D’Arcy, explain the organism’s behavior, not the number of 2005; Montminy, 2005; Newbury, 1954), there steps required to explain it. Th at is, we should be has been much philosophical discussion about the cautious to exhaust all possible explanations for a of each and how they should be applied to behavior that may appear to provide evidence for scientifi c research (Fitzpatrick, 2008; Karin-D’Arcy, a “higher-order” process, but may in fact be due to 2005; Montminy, 2005; Sober, 1998). One level a “lower-level” process. Th is means that we should of misunderstanding applies in thinking that the also guard against arguments by analogy, in which simplest explanation generally refers to what can we are liable to accept any behavior that appears be explained the most simply linguistically or prag- similar to human behavior to have arisen by the matically, rather than referring to what is the sim- same mechanism by which it appears in humans. plest explanatory mechanism for the phenomenon Although it should be noted that Morgan himself in question. Th is “simplest” mechanism in practice did not intend for his canon to be applied against may not be the one that is easiest to explain. For arguments by analogy or (see instance, it may be simpler to explain that your dog Costall, 1993; Fitzpatrick, 2008; Th omas, 1998, was barking at the back door because he wanted you 2001). However, likewise, we should not simply to know that he wanted to go outside. It requires accept a “lower-level” explanation for behavior in a longer explanation to describe the history of lieu of examining whether the behavior may have learning in which the dog has been reinforced for arisen as a result of a “higher-order” process. A simi- standing at the door and barking and has then been lar point is made by Fitzpatrick (2008), who sug- let out into the back yard, and has also failed to gests that Morgan’s canon be abandoned altogether. be reinforced for not standing at the door or not He points to the fact that authors have sometimes barking, and thus has had to learn to connect the preferred “lower-level” explanations for animals’ positive consequences to the combination of both behavior over “higher level” explanations when, behaviors, while also explaining why this level of in fact, there is no objective criteria for doing so,

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simply because of Morgan’s canon (see also chap- critical of why a “negative” or “null” result has been ter 2, this volume). Barrett (chapter 2) reveals how obtained. Is it due to some methodological diffi culty mistakenly confl ating Morgan’s canon with the rule in the study or some experimental artifact, a failure of parsimony allows researchers to justify preferring of proper statistical analysis, and so on? We must be both mentalistic and associationistic accounts of the sure to apply our critical skills to all kinds of results; same behaviors or phenomena on no other (objec- not just the results that we fi nd harder to accept or tive) basis. To be objective, we must apply our prin- those that challenge our expectations more strongly. ciples in all directions. Just as we should not accept We should also be skeptical of results that are in line “higher-order” explanations without considering all with our expectations. Just because the results con- other possible explanations, we should not accept fi rm our hypotheses does not mean that they were “lower-order” explanations without being equally arrived at correctly or that they refl ect reality or a critical. Indeed, it is sometimes the case that we are lack of bias. Indeed, again, the very language that too liberal in assuming that humans make use of we use, describing results as “negative” or “null” and higher-order processes when they are, in fact, using describing processes as “lower” versus “higher” level what we deem lower-order processes to solve prob- or order, indicates a problem with our objectivity lems. Much of what humans do makes use of the as scientists—a problem we must be hypervigilant same association-based learning that we attempt to against. reduce higher-order explanations to, when we feel Researchers have also questioned the validity of researchers have “over ascribed” traits in other spe- results based on the representativeness of the sam- cies. Th e that can be used as animal mod- ples studied. Again here, though, we must be care- els for basic learning processes in humans is because ful not to lodge this criticism, specifi cally when the many of the processes are, in fact, the same, or at studies yield results that contradict our “preferred” least similar (see chapters 12 and 14, this volume). hypotheses and not when they are in line with those Indeed Sheskin and Santos note that researchers same hypotheses or theoretical viewpoints. For may want to reevaluate the work on “fairness” in instance, researchers who work predominantly with primates, when considering that much of what wild animals sometimes call into question results we consider to be morality-based considerations from captive animals, citing a lack of external valid- of equity in humans may also be due to the same ity and cognitive deprivation as a major explana- kinds of frustration eff ects we have attributed to tion for why captive apes may fail to “pass” certain nonhumans (chapter 23 of this volume). Likewise, experimental tasks. For instance in chapter 26 of Warneken and Melis (chapter 21of this volume) dis- this volume, Boesch calls into question results from cuss the diffi culties in attributing altruistic motives Povinelli’s laboratory with seven peer-raised chim- to apparent altruistic behaviors in our closest liv- panzees, citing their lack of “typical” chimpanzee ing relatives, yet the same critiques could easily be socialization and natural environment. He points applied to apparently altruistic behaviors in humans. to the fact that Povinelli’s chimpanzees have often For instance, humans who act kindly to assist others “failed” tasks that other chimpanzees “succeed” at. in need might be motivated to gain friendships or However, this is a commonly stated misinterpre- alliances that might later benefi t themselves, or sim- tation of the results from Povinelli and colleague’s ply enhance their own self image. Lyn (chapter 19 work, even if off the record, and ignores that fact of this volume) pointedly reminds us that critiques that these chimpanzees have often been among the against the ape language research centered on accu- fi rst to demonstrate evidence of natural chimpanzee sations of operantly conditioned responses on the behavior such as gaze following (Povinelli & Eddy, part of ape subjects might apply equally to much of 1997), joint attention (Povinelli & Eddy, 1996b,c), the human language acquisition process. discrimination between those with diff ering inten- Th e same argument should be made in terms of tions (Povinelli, Perilloux, Reaux, & Bierschwale, accepting “null” versus “positive” results. If we are 1998), successful use of tools (Povinelli, 2003), and to be exceedingly critical in accepting evidence for other so-called “positive” fi ndings. However, what the existence of some trait or some behavior with- diff ers between Povinelli’s work and that of many out exhaustively examining other possible explana- others is in the interpretation of the results, not the tions for how the behavior may have emerged by results themselves. For instance, with regard to the accident, by trial and error, or some other manner fi ndings that chimpanzees sometimes discriminated that does not attribute some ability in question to between those who intentionally versus accidentally the organism of study, then we should be equally spilled juice that they off ered to the chimpanzees,

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Povinelli and colleagues (1998) were more likely understanding of which item the dominant animal to interpret the chimpanzees as reading the behav- could see. Of course, they were more likely to ulti- iors rather than the mental states underlying those mately obtain the item that the dominant could behaviors, whereas similar results in analogous para- not see (see also Karin-D’Arcy & Povinelli, 2002; digms were more likely to be interpreted in a man- Povinelli & Vonk, 2003, 2004). Th us, we must be ner more consistent with “higher-order” processes, cautious when concluding that the results diff er such as recognizing the underlying intentions of between laboratories, when, in fact, it may be the the experimenters (e.g., Call, Hare, Carpenter & interpretations and conclusions that diff er, not the Tomasello, 2004; Call & Tomasello, 1998), even performance of the animals. though a behavior-reading account leads to the Th is is not to say that the question of rearing his- same pattern of results (see Povinelli & Vonk, 2003, tory is not an important issue. Certainly, animals 2004). Likewise, results from the “see/not-see” deprived of the need to search for food and mates paradigm (Povinelli & Eddy, 1996a) demonstrated and the opportunity to socialize with their peers that chimpanzees are astute from the fi rst trial at and perhaps parents from birth may be stripped of diff erentiating between human experimenters who the chance to develop normal social behaviors. We were facing them versus those who were facing know this from the early work of Harlow (Harlow, away, and they could learn to discriminate between 1958). Th ese results dovetail with what was learned experimenters in other experimental conditions. about human children growing up in Romanian Th us, Povinelli and colleagues (Reaux, Th eall & orphanages during World War I (Blum, 2002; Povinelli, 1999), following a series of careful con- Nelson et al., 2007), and related work has revealed trol tests, concluded that the chimpanzees learned profound implications for children growing up a series of behavioral rules and were not reasoning under various circumstances of abuse and neglect. about underlying mental states. Th e results of others Children deprived of normal social contact and (Bulloch, Boysen, & Furlong, 2008; Kaminski, Call aff ection display diffi culty demonstrating aff ection & Tomasello, 2004) are consistent with these inter- and maintaining social and romantic relationships pretations but have been interpreted diff erently. A and attachments later in life (Cacioppo & Hawkley, widely cited series of studies arguably responsible 2003). Close physical contact in infancy can also for turning the tide toward accepting continuity in improve later physical health (Cacioppo & Hawkley, mental-state attribution between humans and other 2003; Feldman & Eidelman, 1998). Various depri- apes showed that chimpanzees took competitors’ vation studies with animals and opportunistic stud- line of sight into account when competing for pieces ies of tragic human cases of neglect have revealed of food that dominant animals could or couldn’t see the disparate trajectories taken by those with abnor- (Hare, Call, Agnetta & Tomasello, 2000, Hare, Call mal histories. Although Sell (chapter 4 of this vol- & Tomasello, 2001). Hare and colleagues (Hare et ume) makes a compelling case for why we should al, 2000, 2001) argued that chimpanzees should never treat nature/nurture as a dichotomy, and he is be expected to demonstrate their understanding right—it is a false dichotomy—of course, all devel- of others’ mental states in competitive paradigms, opment is an interaction between the infl uences of not cooperative paradigms, because these are the heredity and the environment, it is still of interest situations in which such abilities would have been to examine the relative contribution of each and most likely to evolve in their natural environments the manner in which certain traits are plastic rather (Hare, 2001). Notwithstanding, the inherent diffi - than canalized. culties with such an argument, which ignores the Th e relatively recent focus on enculturation in very reason that theory of mind might have evolved apes (Bering, 2004; Tomasello & Call, 2004) and to begin with—to allow an organism fl exibility in domestication in canines (Dorey, et al., 2010; Hare, predicting the behaviors of others in a multitude of 2007; Hare et al., 2002, 2010; Udell, et al., 2008; contexts and scenarios—the point we wish to raise Wynne, et al., 2008) emphasizes the importance of at this juncture is as follows: a critical decision was the role of plasticity in evolution. How much are we made regarding the dependent measure in the Hare constrained by the biology of our species, and how et al. studies. Th ese researchers chose to measure much can our cognition be molded by the environ- which food item the subordinate individual man- ment in which we are raised? Can this sculpting be aged to obtain on a given trial, not which food altered within our own ontogeny, or does the shap- item they fi rst attempted to obtain, which would ing take place over generations (Dorey et al., 2010; have been the critical measure to determine their Udell et al., 2008; Wynne et al, 2008)? Miklosi and

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Topal (chapter 11) point out that interspecifi c com- acquired more readily than that in others (Dellarosa parisons of extant canid species have not been con- Cummins & Cummins, 1999; Garcia & Koelling, ducted to date, although these could be informative 1966), and this will likely depend on environmen- in terms of genome/environment interactions. Th ese tal input. Th ey also understand that prior experi- are hot topics in comparative evolutionary psychol- ence will aff ect the manner in which stimuli and ogy today and ones that will be critical to defi ning events are interpreted and processed. We are not questions about the role of genes and environment blank slates, but neither are we immune to the in shaping behavioral and cognitive traits. environment. Miklosi and Topal (chapter 11) place Although few today identify themselves as strict the discussion in context via an interesting contrast behaviorists, many still operate under the same between the eff ects of human socialization on the basic principles that it is not useful to refer to cog- domestic dog—a species selected for sharing the nitive processes operating within the minds of the human social environment—and the “encultur- organism. Th ese same individuals fi nd it a detrac- ated” ape—a species not selectively evolved for such tion from the goals of science to study such topics as an environment, and who may indeed be viewed consciousness, metamemory (chapters 12–15), the- as socially deprived when not raised in the wild ory of mind, (chapters 3 and 27), morality (chapter (Suddendorf & Whiten, 2001). Barrett provides a 23), and so on, because they believe these topics will lengthy exposition in her chapter (chapter 2) of the never be subject to the objective methods that are pitfalls one might encounter in attempting to resur- necessary to provide clarity to the subject matter. rect a strong divide between behaviorist and nativist However, this seems to be a defeatist perspective. positions, particularly under the umbrella of current Titchener once believed that it was not possible comparative and evolutionary research. Indeed, her to study human children or nonhumans or the thoughtful discussion may cause the reader to won- mentally ill because they could not properly intro- der if such a divide ever really existed in any practi- spect (Schultz & Schultz, 2008). However, with cal sense. the advance of methods other than , To study the eff ects of the environment and the psychology became much broader and psycholo- role of genetics on behavior, both idiographic and gists have made progress in the study of human normative approaches can be illuminating. Again, development and disorders, as well as in compara- it is not useful to adopt one approach completely tive psychology. Th ose who hold steadfast to the at the expense of the other. Typically, comparative old behaviorist mantra may fi nd themselves falling psychologists have been restricted to small-n stud- out of favor with the current trend toward cogni- ies because of limited access to the special popula- tive topics in the study of animal behavior (see also tions they work with, or the expense of maintaining chapter 2 of this volume). populations of their animals. Even Skinner, who An extreme nativist position is no more useful worked with more accessible animals, such as rats than an extreme behaviorist position. Ignoring the and pigeons, was the most famous proponent of the contribution of the environment and experience or small-n approach, believing that one should study the interaction between heredity and the environ- small numbers of subjects in exquisite detail to fully ment is akin to assuming an alcoholic is destined appreciate their behaviors, rather than capturing to develop this disorder regardless of whether he small pieces of a problem in a large group of sub- ever takes a drink. In general, extreme positions jects, potentially losing the nuances of the larger have fallen out of favor because they succeed only picture. Issues of access may be less of a problem in ignoring the contribution of other factors to the for evolutionary psychologists who primarily study dependent variables in question. human populations and may study large numbers Th e cognitive movement has taken over much of in various cultures. Even for evolutionary psycholo- psychology, and it is consistent with an evolutionary gists, however, it is important to recognize how the framework (see chapters 2 and 4 of this volume, and individual is aff ected by the larger group, and how Pinker, 1997). Cognitive psychologists tend to be, the group is aff ected by the larger cultural context in part, both nativists and behaviorists. Th at is, they (see Mesoudi & Jensen, chapter 22). Dunbar and embrace both top-down and bottom-up processing Sutcliff e (chapter 6) note that a signifi cant focus in accounts. Th ey understand that all organisms may evolutionary research has neglected to account for be biologically prepared to learn in certain ways the fact that individuals of many species make the about certain types of information and not oth- most important decisions in their lives as part of a ers, and that information in some domains may be social group. Both individual diff erences and the

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larger group context, and the interactions between studies with juvenile chimpanzees indicated that the two factors, must be considered. these chimpanzees were willing and motivated to Evolutionary comparative psychologists must cooperate with human experimenters (Warneken, move away from the study of few select species, such Hare, Melis, Hanus, & Tomsello, 2007; Warneken as the white , the pigeon, the rhesus macaque, & Tomasello; 2006; Warnken & Melis, chapter 21). and the chimpanzee. Th e last decade has witnessed Although it has been noted that these young chim- an explosion of research with various fascinating panzees had been raised and “enculturated” by the species, some demonstrating surprising abilities human experimenters, and thus may have behaved in that they appear to resemble human capacities diff erently than other chimpanzees in diff erent con- despite divergent evolutionary trajectories. Emery texts, a follow up study showed similar results when compares the abilities of apes and corvids (chapter chimpanzees interacted with less familiar humans 5) and discusses the possibility of convergent evolu- (Warneken et al, 2007). Chimpanzees do not share tion as the driving mechanism giving rise to simi- food in studies of prosocial behavior (Jensen et al., lar social cognitive skills. Others reveal surprising 2006; Silk et al., 2005; Vonk et al., 2008), but may capacities for advanced cognitive skills in species as do so when paired with off spring or individuals who distant from humans as insects (Cocroft & Sullivan- display a particular need, such as individuals in poor Beckers, chapter 18), cephalopods (Mather, chapter health or who are food deprived. Studies that can 7), and reptiles (Wilkinson & Huber, chapter 8). track whether reciprocal exchanges take place may As Jaakola (chapter 9) acknowledges, despite recent provide more insight into the and his- attempts to focus our eff orts on these many inter- tories of such individuals (see also Boesch, chapter esting and diverse species, we have barely scratched 26; Silk & House, chapter 20). Such studies with the tip of the iceberg. As she reviews, although few individuals may lead to conclusions that say cetaceans have received a fair bit of interest, only more about individuals and their unique histories bottlenose have been extensively studied, than about species’ tendencies or traits as a whole. and even the data on this species is patchy, at best. Miklosi and Topal also point out that: Th us, for comparative psychologists, drawing con- Th e hunt for the “cleverest” species or a species that clusions about a species’ capacities based on the per- “outperforms” another one makes the fi eld more formance of one, or few members, of that species similar to a horse race than a scientifi c enterprise. can lead to misleading assumptions. One would not Scientists should be aware of the problems of want to draw conclusions about the mental capaci- comparing a few individuals of any species who may ties of the human race based on an Einstein or a diff er not only in their genetic constitution but with severely mentally disabled individual, any more respect to many other factors. One key example for than one would want to conclude that orangutans this is the naïve comparison of dog breeds, in which were mentally inferior to gorillas when comparing a any diff erence is rapidly attributed to the specifi c single unmotivated socially isolated and cognitively “genes” disregarding nonspecifi c genetic eff ects (e.g., deprived orangutan to a single socially enriched and diff erences in size) or an array of environmental well-trained, motivated young gorilla. Individual infl uence that may aff ect the two dog populations in diff erences have not received wide attention in com- diff erent ways parative studies, despite their profound implications (chapter 11, pXXX-XXX.00). for the fi eld (see also Vonk & Povinelli, 2011). For instance, much of what was known about parrots We cannot ignore individual diff erences and fac- was based on the work of a single individual with a tors other than species diff erences when working single African grey parrot (Pepperberg, chapter with small-n samples, and we cannot succumb to 16). Alex’s cognitive feats lead many to deem parrots “Holy Grail” pursuits. the “intelligent” birds. Only recently have corvids Th ese issues we raise are not independent of each been deemed the “other intelligent” birds despite other. Whether individuals are studied in the wild being the central fi gures in myths and folklore for or in the laboratory, have natural rearing histories, centuries (Emery, chapter 5). However, many other or have been aff ected by “alternative” rearing or bird species are relatively untested, and only fairly testing environments, can have signifi cant eff ects on recently have other members of these families been the outcomes of our studies, and the conclusions tested in a variety of experimental paradigms. we draw from them. No single approach will be Here it is also important to consider notewor- perfect and will protect against all threats to inter- thy examples of recent research. Warneken et al’s nal or external validity. Both fi eld and laboratory

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approaches contribute diff erent elements to our an evolutionary perspective, but, again, a dichoto- understanding of a species’ behavior and cognition. mous take is not the most productive here. First, Laboratory approaches sometimes have an advan- we must identify what dispositions are within the tage when they can control confounding variables repertoires of species and only then can we ask why and examine possible causes and motivations for this would be so. Each type of question is the com- individual subjects’ behaviors or choices in a single plement of the other; neither exists in isolation or experimental task (see also Silk & House, chapter operates in a vacuum. Barrett makes a cogent argu- 20). Of course, researchers studying a species in ment about why an organism’s structure or physiol- the wild can utilize experimental methods to rule ogy is often as vital as their brain for determining out many confounding variables, an approach that the manner in which they represent and process has been demonstrated brilliantly by Cheney and stimuli and events in their environments (chapter Seyfarth over the years (chapter 27) and is exem- 2). Th at is, an organism’s physiology, particularly plifi ed in the work of their protégée (Zuberbühler, with regard to its sensory systems, must also be chapter 17). However, it is never as possible to be sculpted for taking in information from the envi- aware of the subjects’ life histories and exposure to ronment, sometimes in a manner that reduces the objects, events, and other individuals when they need for extensive cognitive processing and yet still have been raised outside of the laboratory, making leads to adaptive responding (see chapter 2 for a it more diffi cult to rule out explanations of learning more detailed discussion). In any case, the brain, outside the experimental context. However, others albeit an amazing computational device, does not will argue that an ecological approach that places operate in isolation from the other physiological the animal in its natural social and physical envi- adaptations of the organism. Miklosi and Topal ronment is the only appropriate approach for the (chapter 11) point to the emergence of cognitive evolutionary study of mental continuity (chapters , as an attempt to explain functional behav- 3 and 26). Mesoudi and Jensen (chapter 22) reveal iors at the level of their underlying mechanisms. As how topics such as cooperation and punishment they so rationally declare, have been examined in both experimental and fi eld From the functional viewpoint, no matter if dog-wolf settings, in combination, giving a rich picture of the diff erences and dog-human similarities lie in specifi c evolutionary forces giving rise to altruistic behaviors (qualitative) changes in the dogs’ cognitive processing (or the lack thereof) in our own and closely related or far less specifi c (quantitative) changes in the species. Hopper and Whiten (chapter 24) have also attention and memory skills and associative learning taken a combined approach, studying cultural learn- capacities, and so forth, in reviewing parallels ing in both the laboratory and in the fi eld, and they between human and dog behavior, it is better to argue that their two-pronged approach has revealed refrain from premature interpretation of the cognitive that humans are not alone in demonstrating cul- processes that control the observed performance ture—an assumption that was held for the greater (chapter 11, p.xxx). part of the last century. Other topics, such as theory of mind, have simply not been studied extensively Again, one needs to understand wherein diff er- outside the laboratory, making it diffi cult to specu- ences lie before one can speculate about why, or for late about the adaptive function of such a mecha- what purpose, are the target traits or behaviors. nism and its selective pressures, as noted by Cheney And perhaps that is the key message here: research and Seyfarth (chapter 27). should not pivot on false dichotomies or mutu- It is not just the methodology of choice that cre- ally exclusive endpoints that allow for no middle ates tension between researchers. Th e determination ground. Research does not exist in a vacuum, and of what the central questions should be also causes it is least productive when researchers implicitly friction. As in the early , some assume that it does. We have the benefi t today of an researchers have structuralist leanings, believing ever-advancing wealth of technology in which we that the critical goal should be to identify traits, can easily use the Internet to download the latest capacities, and behaviors to describe and under- article from journals or web sites, and we can e-mail stand similarities and diff erences between species; authors or view video of experiments. Th ere is no in other words, to answer questions about what is. excuse for a failure to appreciate what goes on in a Others researchers have functionalist leanings and closely related discipline or to join the two to wed aim to answer questions about what for, and why. their strengths. Evolutionary psychology has taken Th e latter position may seem more consistent with advantage of advances in closely related fi elds such

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as , computational science, and Call, J., Hare, B., Carpenter, M., Tomasello, M. (2004). neuroscience to further understanding of human ‘Unwilling’ versus ‘unable’: Chimpanzees’ understand- and nonhuman cognitive processes. Dunbar and ing of human intentional action. Developmental Science, 7, 488–498. Sutcliff e’s approach to the study of the evolution of Call, J., Tomasello, M. (1998). Distinguishing intentional from the social brain is a good example of the melding accidental actions in orangutans, chimpanzees, and human of neuroscience, , and evolution- children. Journal of Comparative Psychology, 112, 192–206. ary theory (chapter 6). It is time that comparative Costall, A. (1993). How Llyod Morgan’s canon backfi red. Journal psychologists similarly incorporate advances in of the History of the Behavioral Sciences, 29, 113–122. Dellarosa Cummins, D. & Cummins, R. (1999). Biological closely aligned fi elds into their methodologies and preparedness and evolutionary explanation. 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