Papers by Dorothy Fragaszy
The present paper provides an integrative theory of actions and motor programs for skill in tool ... more The present paper provides an integrative theory of actions and motor programs for skill in tool use, construction, and language. We analyze preconditions for action as well as making their effects (postconditions) explicit, emphasizing the "how" of action details as well as the "what" of motor programs, aided by conceptual analysis of several brain modeling efforts. The theory is exemplified by analysis of the subtractive construction involved in percussive tooling by capuchin monkeys and Oldowan and Acheulean stone tool making by protohumans before turning to the additive construction of hafted tools. A complementary analysis focused on the construction of bird nests explores the notion of "image" and "stage" in construction. We offer a brief comparison with birdsong before arguing for a very different relation between communication and construction in humans. Pantomime lifts manipulation from practical to communicative action in protohumans, and we consider the role of pedagogy before offering hypotheses on the emergence of human language that suggest how language may have evolved from manual skills. We note that language provides an open-ended means for devising innovations in tool use and construction, but reiterate the importance of this framework for diverse future studies in ethology and comparative psychology.
Nearly 100 years ago, Wood Jones ( 1920 ) characterized the hand as a specialized sensory organ a... more Nearly 100 years ago, Wood Jones ( 1920 ) characterized the hand as a specialized sensory organ and the use of the hands in exploration as a defi ning characteristic of primates. Thus, from the beginning, researchers have investigated how primates use their hands to touch and handle objects, as well as during locomotion. Understanding how primates use their hands is fundamental to reconstructing and interpreting the evolution of the order to which humans belong to (Napier 1960 , 1961 , 1980 ). Primates were present in the Eocene, feeding and moving predominantly on thin and fl exible terminal branches (Cartmill 1974 ; Sussman 1991 ; Sussman et al. 2013 ; see Chap. 14 ). They used both hands and feet to locomote in this environment and the hands to feed. Prehension of small objects (such as insects or fruits) by one hand is considered a primitive characteristic of primates (Washburn 1951 ; Napier 1961 , 1980 ) and is integral to feeding in all living primates. However, this character...
American Journal of Primatology
Tool use in humans can be optional, that is, the same person can use different tools or no tool t... more Tool use in humans can be optional, that is, the same person can use different tools or no tool to achieve a given goal. Strategies to reach the same goal may differ across individuals and cultures and at the intra‐individual level. This is the first experimental study at the intra‐individual level on the optional use of a tool in wild nonhuman primates. We investigated optional tool use by wild bearded capuchins (Sapajus libidinosus) of Fazenda Boa Vista (FBV; Piauí, Brazil). These monkeys habitually succeed in cracking open the mesocarp of dry cashew nuts (Anacardium spp.) by pounding them with stones and/or by biting. We assessed whether availability of a stone and resistance of the nut affected capuchins' choice to pound or to bite the nuts and their rates of success. Sixteen capuchins (1–16 years) received small and large dry cashew nuts by an anvil together with a stone (Stone condition) or without a stone (No‐Stone condition). In the Stone conditions, subjects used it to crack the nut in 89.1% (large nuts) and 90.1% (small nut) of the trials. Nut size significantly affected the number of strikes used to open it. Availability of the stone significantly increased the average percent of success. In the No‐Stone conditions, monkeys searched for and used other percussors to crack the nuts in 54% of trials. In all conditions, age affects percentage of success and number of strikes to reach success. We argue that exclusive use of stones in other sites may be due to the higher abundance of stones at these sites compared with FBV. Since capuchins opened cashews with a tool 1–2 years earlier than they succeed at cracking more resistant palm nuts, we suggest that success at opening cashew nuts with percussors may support the monkeys' persistent efforts to crack palm nuts.
International Journal of Primatology
Animal traditions are increasingly threatened by human impact on natural habitats, posing a chall... more Animal traditions are increasingly threatened by human impact on natural habitats, posing a challenge to conservation policies. In northeastern Brazil, bearded capuchins (Sapajus libidinosus) inhabiting the Cerrado–Caatinga biome of Fazenda Boa Vista use stone hammers and anvils to crack open palm nuts and other encased foods. The same species inhabiting the mangroves of Morro do Boi ambush crabs and process them using wooden hammers and anvils. These traditions are gradually acquired by young capuchins exposed to the tool using activity of skilled older group members. Changes in land cover have threatened the persistence of this species, where these rare tool-use traditions occur. To assess land cover changes over the past 30 years, we analyzed a time series of remotely sensed imagery and quantified trends in land cover and agriculture across both study sites. We also developed a predictive model to forecast future changes in land cover by 2034. Our results show that agriculture increased by more than 300% in both sites from 1987 to 2017. If current trends continue in Morro do Boi, only 42% of forest (0.15 km2) will remain, which is insufficient to support the resident population of capuchins. In Fazenda Boa Vista, most of the land suitable for agriculture has already been used for that purpose. If private conservation efforts at Fazenda Boa Vista are to be effective through 2034, agricultural use should not be expanded any further. Imminent erosion and loss of natural vegetation will exacerbate the current situation, even if agriculture is not expanded. Our study is an example of the need for conservation to take behavioral traditions into account, as they are not widespread across the species distribution.
American journal of primatology, 2018
Extractive foraging is a skill young capuchin monkeys learn over time. A key unknown is whether u... more Extractive foraging is a skill young capuchin monkeys learn over time. A key unknown is whether unskilled individuals occupy spatial positions that increase their opportunities to learn. We observed the spatial positions of individuals in a group of capuchin monkeys in Northeastern Brazil. To improve our understanding of the relationship between learning by young capuchin monkeys and inter-individual distance, we investigated the associations between the proximity of individuals and their age, activity, and proficiency at extractive foraging. To do this, we used one form of extractive foraging, opening palm nuts, as an index of proficiency at all types of extractive foraging. Our results indicate that, in the subset of the data where dyads consisted of one proficient individual and a partner with any level of proficiency, the distance between individuals was predicted by their foraging activity (i.e., extractive foraging, other foraging, or not foraging). In those dyads, the profici...
Experimental brain research, Jan 14, 2018
Perception of properties of a grasped object via dynamic touch (wielding) contributes to dexterit... more Perception of properties of a grasped object via dynamic touch (wielding) contributes to dexterity in tool use (e.g., using a hammer, screwdriver) and sports (e.g., hockey, tennis). These activities differ from simple object manipulation in that they involve making contact with an intended target. In the present study, we examined whether and how making (percussive) contact with a target influences perception of the length of a grasped object via dynamic touch. Making contact with a target by the tip resulted in a more accurate perception of the length than simple wielding. However, making contact with the target at a point along the length did not influence the accuracy of perception. These findings suggest that the location of a grasped object's effector influences perception of properties of that object via dynamic touch. We discuss these findings in terms of time-varying properties of vibrations generated by the percussive contact of the grasped object and target.
Attention, Perception, & Psychophysics
Rotational inertia-a mechanical quantity that describes the differential resistance of an object ... more Rotational inertia-a mechanical quantity that describes the differential resistance of an object to angular acceleration in different directions-has been shown to support perception of the properties of that object through dynamic touch (wielding). The goal of the present study was to examine if perception of the length of an object through dynamic touch depends on its rotational inertia, independent of the medium in which it is wielded. The participants (n = 14) wielded 12 different objects held in air or completely immersed in water and reported perceived lengths of those objects. Each object consisted of a rod of a particular density with a particular number of stacked steel rings attached at a particular location along its length. Perceived length was invariant across medium. In addition, a singlevalued function of the major eigenvalue, I 1 , and the minor eigenvalue, I 3 , of the rotational inertia, I, of the 12 objects predicted the perceived lengths of those objects in both air and water, and the perceived lengths were invariant across the two media. These results support the hypothesis that the informational support for perception of the length of an object through dynamic touch is invariant across changes in the medium.
Nature Ecology & Evolution
Journal of Comparative Psychology, 2017
Female wild bearded capuchins (Sapajus libidinosus) living at Serra da Capivara National Park (SC... more Female wild bearded capuchins (Sapajus libidinosus) living at Serra da Capivara National Park (SCNP) that use stone and stick tools during foraging occasionally toss or throw stones at the male during courtship. We report similar behaviors in a different population that uses stones as tools in foraging. We video-recorded the sexual behavior of four females (27 days during nine proceptive periods) belonging to a group of wild capuchins living in Fazenda Boa Vista (FBV), 320 km from SCNP. Three females used stones or branches when they solicited the alpha male (79 episodes). The female that did not use objects was the sole female to solicit a subordinate male. The vast majority of episodes (95%) involved pushing or dropping branches, both loose and attached to the tree, toward the male. Females used objects only during the one-way courtship phase, before the male reciprocated the female's solicitations. In 93% of the episodes in which a female used objects, she performed affiliative behaviors immediately before or after using the objects. We conclude that throwing or pounding stones and pushing or dropping branches by females in SCNP and FBV in the sexual context have a clear affiliative meaning (to attract the male's attention). Given the tool-using status of both populations where these behaviors have been reported, it is important to determine whether they appear in populations that do not use tools, or are restricted to populations already primed to use objects in other contexts.
International Journal of Comparative Psychology, Dec 31, 2003
Comparative and developmental psychology have impacted one another for well over 100 years. Resea... more Comparative and developmental psychology have impacted one another for well over 100 years. Researchers have studied developmental processes of humans and nonhumans to formulate evolutionary theories and to determine the contributions of hereditary and experiential factors at ontogenetic and phylogenetic levels. We discuss current directions in comparative and developmental research that attend to micro-developmental processes and ecological contexts as sources of variability in humans and nonhumans. This research has been a segue into studies of behavior that are integrative in scope, such the family of systems theories, which cross disciplinary boundaries. We present findings from our research on instrumental manual activity in human and nonhuman primates from a systems perspective, and argue that integrative systems approaches hold promise for understanding individuals and development of behavior across species.
Developmental Psychobiology, 2016
Hammering with a hand tool appears early in life. Skillful hammering involves accommodating movem... more Hammering with a hand tool appears early in life. Skillful hammering involves accommodating movements to properties of the hammer, orienting the hammer's head to the item to be struck, and maintaining stable posture during forceful action with the arm(s). We aimed to characterize development of these abilities in young children (12, 18, and 24 months old). Children struck at a peg with a hammer held in the hand or a hammer attached to a handle. Children struck more frequently with a hard hammer surface than a soft one, and more frequently (although less accurately) with handled hammers than with non-handled hammers. Developmental differences were evident in accuracy, number of strikes, and kinematic parameters, especially with the handled object. Children's ability to use objects for forceful and accurate percussion changed measurably over the second year, in tandem with improving postural stability and greater motion of the elbow.
American journal of physical anthropology, Sep 2, 2016
Expert tool users are known to adjust their actions skillfully depending on aspects of tool type ... more Expert tool users are known to adjust their actions skillfully depending on aspects of tool type and task. We examined if bearded capuchin monkeys cracking nuts with stones of different mass adjusted the downward velocity and the height of the stone when striking palm nuts. During a field experiment carried out in FBV (Piauí, Brazil), eight adult wild capuchin monkeys (five males) cracked Orbygnia nuts of varied resistance with hammer stones differing in mass. From recorded videos, we identified the highest strike per nut-cracking episode, and for this strike, we calculated the height to which the monkey lifted the stone, the maximum velocity of the stone during the downward phase, the work done on the stone, and the kinetic energy of the strike. We found that individual capuchins achieved average maximum kinetic energy of 8.7-16.1 J when using stones between 0.9 and 1.9 kg, and maximum kinetic energy correlated positively with mass of the stone. Monkeys lifted all the stones to an ...
Primates; journal of primatology, Jan 5, 2016
The ability to carry objects has been considered an important selective pressure favoring the evo... more The ability to carry objects has been considered an important selective pressure favoring the evolution of bipedal locomotion in early hominins. Comparable behaviors by extant primates have been studied very little, as few primates habitually carry objects bipedally. However, wild bearded capuchins living at Fazenda Boa Vista spontaneously and habitually transport stone tools by walking bipedally, allowing us to examine the characteristics of bipedal locomotion during object transport by a generalized primate. In this pilot study, we investigated the mechanical aspects of position and velocity of the center of mass, trunk inclination, and forelimb postures, and the torque of the forces applied on each anatomical segment in wild bearded capuchin monkeys during the transport of objects, with particular attention to the tail and its role in balancing the body. Our results indicate that body mass strongly affects the posture of transport and that capuchins are able to carry heavy loads ...
Animal Cognition, 2015
Communicative competence is one measure of an individual&... more Communicative competence is one measure of an individual's ability to navigate conversations with social partners. The current study explored the possibility of basic communicative competence in a non-mammal speaker, a speech-using African Grey parrot. Spontaneous conversations between one Grey named Cosmo and her caregiver were recorded, from which three corpora (i.e., bodies of text) of Cosmo's vocalizations were developed: (1) Baseline: Vocalizations containing no requests, (2) Ignored Requests: Vocalizations immediately following Cosmo's caregiver ignoring Cosmo's requests, and (3) Denied Requests: Vocalizations immediately following Cosmo's caregiver denying Cosmo's requests. The distributions of social (e.g., "I love you," kiss sounds) and nonsocial (e.g., answering machine beeps, "That's squirrel") vocalizations, as well as speech and nonword vocalizations, were statistically different across the three corpora. Additionally, qualitative analysis of the datasets indicated Cosmo was persistent in repeating vocalizations when denied and ignored, and interrupted her caregiver more often when requests were denied compared to ignored. Neither repetition nor interruption occurred during the Baseline conversations. The data indicate that despite the outcome being the same (i.e., request was unmet), Cosmo treated an ignored request differently than a denied request, modifying her vocalizations in accord with the specific context. Such modification is evidence of basic communicative competence.
American journal of primatology, Jan 5, 2015
Body mass is fundamental for understanding growth, health, and aspects of life history but record... more Body mass is fundamental for understanding growth, health, and aspects of life history but records of body mass are rarely available for wild primates. We documented the body mass of all individuals in a group of wild bearded capuchin monkeys (Sapajus libidinosus) at annual intervals for seven consecutive years. Sexual dimorphism in body mass was more pronounced than reported in the literature for adults in this genus: females in our sample were relatively light (average 2.1 kg), while males had average body mass (3.5 kg). Three other notable differences between males and females were evident. First, males grew more rapidly and for a longer period than females. We estimate that males attained full body mass at 9.8 years of age and females at 7.5 years. Second, males showed greater inter-individual variability than females in growth rates and adult mass. Third, males gained about 20% above their baseline body mass upon becoming alpha, and lost that amount when they lost that status, ...
International Journal of Comparative Psychology, 1995
Behavioral states and their organization in 5-week old squirrel monkeys and 8-week old capuchin m... more Behavioral states and their organization in 5-week old squirrel monkeys and 8-week old capuchin monkeys was evaluated. Infants at these ages are not quite at the threshold, under species-normal rearing conditions, of independent locomotion. Two age-matched infants of each species were observed continuously for a 5-day period while cared for by their mothers in their natal social groups, or while cared for by humans and housed in an incubator on a stationary support. All four infants spent similar proportions of time sleeping, drowsy, nursing, and awake. Hand-reared infants were more frequently awake and active with their hands, cocked their heads more often, and slept in shorter bouts than their mother-reared counterparts. All infants exhibited a positive correlation during the daylight hours between the duration of time in an alert quiet state and the duration of time being moved by a carrier. In addition to providing detailed information about the temporal characteristics of state organization and activity within subjects, the findings suggest the kinds of alterations in activity which can result in these species when artificial (largely stationary) rearing regimes are experienced. Many of the alterations can be interpreted as compensatory self-stimulation. The alterations are apparently different in the species studied here from those described for other species, principally macaques, experiencing similar artificial rearing regimes. The focus of this report is the temporal organization of behavioral states and activity in infant monkeys. One aim is to provide some detailed information for species not well represented in this literature. A second aim is to consider in a preliminary fashion if rearing regime (maternal, species-normal; or by humans, called hand-rearing) affects the temporal organization of behavioral states and activity in young monkeys in the short term. We were particularly interested to see if (a) durations and rhythmicity of states and (b) frequency of activity would be influenced by rearing regimes.
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Papers by Dorothy Fragaszy