A Comparative Study of the Use of Visual Communicative Signals in Interactions Between Dogs (Canis familiaris) and Humans and Cats (Felis catus) and Humans.

Dogs' (Canis familiaris) and cats' (Felis catus) interspecific communicative behavior toward humans was investigated. In Experiment 1, the ability of dogs and cats to use human pointing gestures in an object-choice task was compared using 4 types of pointing cues differing in distance between the signaled object and the end of the fingertip and in visibility duration of the given signal. Using these gestures, both dogs and cats were able to find the hidden food; there was no significant difference in their performance. In Experiment 2, the hidden food was made inaccessible to the subjects to determine whether they could indicate the place of the hidden food to a naive owner. Cats lacked some components of attention-getting behavior compared with dogs. The results suggest that individual familiarization with pointing gestures ensures high-level performance in the presence of such gestures; however, species-specific differences could cause differences in signaling toward the human. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Molecular heterogeneity of Vicia villosa-recognized perineuronal nets surrounding pyramidal and nonpyramidal neurons in the guinea pig cerebral cortex

This study examined the influence of trunk recruitment on the kinematic characteristics of pointing movements. The distribution of final positions of the hand, the extent and direction of the hand trajectory was basically preserved when trunk movement was combined with arm pointing. These effects were observed during pointing not only with but also without vision. The results imply that two functionally independent units of coordination are used in pointing regardless of visual feedback-one producing arm movement to the target (the reaching synergy) and the other coordinating trunk and arm movements diminishing the influence of the trunk on the arm endpoint trajectory (the compensatory synergy).     

Nonenculturated Orangutans' (Pongo pygmaeus) Use of Experimenter-Given Manual and Facial Cues in an Object-Choice Task.

Several experiments have been performed, to examine whether nonhuman primates are able to make use of experimenter-given manual and facial (visual) cues to direct their attention to a baited object. Contrary to the performance of prosimians and monkeys, great apes repeatedly have shown task efficiency in experiments such as these. However, many great ape subjects used have been "enculturated" individuals. In the present study, 3 nonenculturated orangutans (Pongo pygmaeus) were tested for their ability to use experimenter-given pointing, gazing, and glancing cues in an object-choice task. All subjects readily made use of the pointing gesture. However, when subjects were left with only gazing or glancing cues, their performance deteriorated markedly, and they were not able to complete the task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pointing to kinesthetic targets in space

An experiment investigated in human adults the sensorimotor transformation involved in pointing to a spatial target identified previously by kinesthetic cues. In the "locating phase," a computer-controlled mechanical arm guided the left [condition LR (left-right)] or right [condition RR (right-right)] finger of the blindfolded participant to one of 27 target positions. In the subsequent "pointing phase," the participant tried to reach the same position with the right finger. The final finger position and the posture of the arm were measured in both conditions. Constant errors were large but consistent and remarkably similar across conditions, suggesting that, whatever the locating hand, target position is coded in an extrinsic frame of reference (target position hypothesis). The main difference between the same-hand (RR) and different-hand (LR) conditions was a symmetric shift of the pattern of endpoints with respect to the midsagittal plane. This effect was modeled accurately by assuming a systematic bias in the perception of the postural angles of the locating arm. The analysis of the variable errors indicated that target position is represented internally in a spherical coordinate system centered on the shoulder of the pointing arm and that the main source of variability is within the planning stage of the pointing movement. Locating and pointing postures depended systematically on target position. We tested qualitatively the hypothesis that the selection of both postures (inverse kinematic problem) is constrained by a minimum-distance principle. In condition RR, pointing posture depended also on the locating posture, implying the presence of a memory trace of the previous movement. A scheme is suggested to accommodate the results within an extended version of the target position hypothesis.     

Making inferences about the location of hidden food: Social dog, causal ape.

Domestic dogs (Canis familiaris) and great apes from the genus Pan were tested on a series of object choice tasks. In each task, the location of hidden food was indicated for subjects by some kind of communicative, behavioral, or physical cue. On the basis of differences in the ecologies of these 2 genera, as well as on previous research, the authors hypothesized that dogs should be especially skillful in using human communicative cues such as the pointing gesture, whereas apes should be especially skillful in using physical, causal cues such as food in a cup making noise when it is shaken. The overall pattern of performance by the 2 genera strongly supported this social-dog, causal-ape hypothesis. This result is discussed in terms of apes' adaptations for complex, extractive foraging and dogs' adaptations, during the domestication process, for cooperative communication with humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dolphins (Tursiops truncatus) comprehend the referential character of the human pointing gesture.

The authors tested a dolphin's (Tursiops truncatus) understanding of human manual pointing gestures to 3 distal objects located to the left of, to the right of, or behind the dolphin. The human referred to an object through a direct point (Pd), a cross-body point (Px), or a familiar symbolic gesture (S). In Experiment 1, the dolphin responded correctly to 80% of Pds toward laterally placed objects but to only 40% of Pds to the object behind. Responding to objects behind improved to 88% in Experiment 2 after exaggerated pointing was briefly instituted. Spontaneous comprehension of Pxs also was demonstrated. In Experiment 3, the human produced a sequence of 2 Pds, 2 Pxs, 2 Ss, or all 2-way combinations of these 3 to direct the dolphin to take the object referenced second to the object referenced first. Accuracy ranged from 68% to 77% correct (chance?=?17%). These results established that the dolphin understood the referential character of the human manual pointing gesture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pivots for pointing: Visually-monitored pointing has higher arm elevations than pointing blindfolded.

Observers pointing to a target viewed directly may elevate their fingertip close to the line of sight. However, pointing blindfolded, after viewing the target, they may pivot lower, from the shoulder, aligning the arm with the target as if reaching to the target. Indeed, in Experiment 1 participants elevated their arms more in visually monitored than blindfolded pointing. In Experiment 2, pointing to a visible target they elevated a short pointer more than a long one, raising its tip to the line of sight. In Experiment 3, the Experimenter aligned the participant's arm with the target. Participants judged they were pointing below a visually monitored target. In Experiment 4, participants viewing another person pointing, eyes-open or eyes-closed, judged the target was aligned with the pointing arm. In Experiment 5, participants viewed their arm and the target via a mirror and posed their arm so that it was aligned with the target. Arm elevation was higher in pointing directly. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Spatial memory of domestic dogs (Canis familiaris) for hidden objects in a detour task.

Spatial memory of domestic dogs (Canis familiaris) for hidden objects was investigated via a visible displacement problem of object permanence with a detour paradigm. Experiment 1 showed that dogs were able to spontaneously locate a disappearing object in a detour situation. In Experiments 2 and 3, dead reckoning and allocentric spatial information were put in conflict. Results revealed that dogs simultaneously encoded both sources of information when they had to bypass an obstacle to locate a hidden object. Experiment 3 also revealed that, over the course of testing, dogs gradually learned to rely predominantly on allocentric cues when the detour involved several reorientations. The current study reveals that spatial memory of dogs for hidden objects in a detour task was guided by flexibility in processing spatial information. Dogs could simultaneously encode dead reckoning and allocentric information to locate a disappearing object and used them hierarchically according to the complexity of the detour they encountered in the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comprehension of signs by dolphins (Tursiops truncatus).

The authors assessed the ability of 6 captive dolphins (Tursiops truncatus) to comprehend without explicit training 3 human communicative signs (pointing, directed gaze, and replica). Pointing consisted of indicating the target item with the index finger and a fully extended arm. Directed gaze consisted of orienting the head and eyes toward the target item while the rest of the body remained stationary. The replica signal consisted of holding up an exact duplicate of the target item. On the initial series of 12 trials for each condition, 3 dolphins performed above chance on pointing, 2 on gaze, and none for replica. With additional trials, above chance performance increased to 4 dolphins for pointing, 6 for gazing, and 2 for replica. The replica sign seemed to be the most taxing for them (only 2 dolphins achieved results significantly above chance). Taken together, these results indicate that dolphins are able to interpret untrained communicative signs successfully. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modulation of the action control system by social intention: Unexpected social requests override preplanned action.

Four experiments investigated the influence of a sudden social request on the kinematics of a preplanned action. In Experiment 1, participants were requested to grasp an object and then locate it within a container (unperturbed trials). On 20% of trials, a human agent seated nearby the participant unexpectedly stretched out her arm and unfolded her hand as if to ask for the object (perturbed trials). In the remaining 3 experiments, similar procedures were adopted except that (a) the human was replaced by a robotic agent, (b) the gesture performed by the human agent did not imply a social request, and (c) the gaze of the human agent was not available. Only when the perturbation was characterized by a social request involving a human agent were there kinematic changes to the action directed toward the target. Conversely, no effects on kinematics were evident when the perturbation was caused by the robotic agent or by a human agent performing a nonsocial gesture. These findings are discussed in the light of current theories proposed to explain the effects of social context on the control of action. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The whole-hand point: The structure and function of pointing from a comparative perspective.

Pointing by monkeys, apes, and human infants is reviewed and compared. Pointing with the index finger is a species-typical human gesture, although human infants exhibit more whole-hand pointing than is commonly appreciated. Captive monkeys and feral apes have been reported to only rarely "spontaneously" point, although apes in captivity frequently acquire pointing, both with the index finger and with the whole hand, without explicit training. Captive apes exhibit relatively more gaze alternation while pointing than do human infants about 1 year old. Human infants are relatively more vocal while pointing than are captive apes, consistent with paralinguistic use of pointing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit processing of somaesthetic information: a dissociation between where and how?

We present the case of a patient with a lesion of the thalamus who was completely anaesthetized on his right side. He was unable to detect and describe a tactile stimulus applied to his affected right arm, but could direct his normal left hand toward the specific right hand site where the stimulus had been applied when so instructed ('blind touch'). Strikingly, this pointing ability disappeared when the patient had to indicate on a picture of an arm where the stimulus was applied, and when he had to name the stimulus location during his pointing. Similar results were also obtained for localizing the unfelt fingertip ('blind proprioception'). Neuropsychological case studies have demonstrated that brain lesions can produce reciprocal dissociations between object identification (what is the object) and object-oriented action (how to direct a movement to the object). Along these lines, it is suggested that our patient exhibited a dissociation between a 'where' system and a 'how' system for tactile and proprioceptive stimuli.     

The perception of limb orientation depends on the center of mass.

Three experiments were conducted to test the hypothesis that the perception of limb orientation depends on inertial eigenvectors against the alternative that it depends on the center of mass. In all experiments, each participant pointed at visible targets with his or her occluded right arm while center-of-mass and inertial eigenvectors were manipulated independently. In Experiments 1 and 2, the arm was constrained to rotate exclusively about the shoulder, whereas in Experiment 3, the arm was allowed to rotate freely about both the shoulder and the elbow. The mechanical manipulations were applied either in the horizontal (Experiments 1 and 3) or vertical (Experiment 2) plane. Across experiments, pointing direction was affected by the center of mass and not by the inertial eigenvectors, albeit that simultaneous manipulation of both resulted in a more pronounced pointing bias than the isolated center-of-mass manipulation. These findings challenge the inertial eigenvector hypothesis and suggest that the center of mass plays a generic role in the perception of limb orientation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The structure of somatosensory information for human postural control

The goal of the present study was to determine the properties of the somatosensory stimulus that alter its temporal coupling to body sway. Six standing subjects were tested while touching a metal plate positioned either directly in front of or lateral to the subject. In each condition, the plate moved 4 mm at 0.2 Hz in either the medial-lateral (ML) or anterior-posterior direction (AP). The results showed that coupling between body sway and touch plate movement was strongest when the touch plate moved in a direction along the longitudinal axis of the arm. Coupling strength was weaker when the touch plate moved perpendicular to the longitudinal axis of the arm. The results consistently show that a radial expansion stimulus was more effective than a lamellar-type stimulus at the fingertip. Moreover, somatosensory information from a surface is interpreted in terms of the orientation of the contact limb and the potential degrees of freedom available through its movement.     

Reaching movements with similar hand paths but different arm orientations. I. Activity of individual cells in motor cortex

This study shows that the discharge of many motor cortical cells is strongly influenced by attributes of movement related to the geometry and mechanics of the arm and not only by spatial attributes of the hand trajectory. The activity of 619 directionally tuned cells was recorded from the motor cortex of two monkeys during reaching movements with the use of similar hand paths but two different arm orientations, in the natural parasagittal plane and abducted into the horizontal plane. Nearly all cells (588 of 619, 95%) showed statistically significant changes in activity between the two arm orientations [analysis of variance (ANOVA). P < 0.01]. A majority of cells showed a significant change in their overall level of activity (ANOVA, main effect of task, P < 0.01) between arm orientations before, during, and after movement. Many cells (433 of 619, 70%) also showed a significant change in the relation of their discharge with movement direction (ANOVA, task x direction interaction term, P < 0.01) during movement, including changes in the dynamic range of discharge with movement and changes in the directional preference of cells that were directionally tuned in both arm orientations. Similar effects were seen for the discharge of cells while the monkey maintained constant arm postures over the different peripheral targets with the use of different arm orientations. Repeated data files from the same cell with the use of the same arm orientation showed only small changes in the level of discharge or in directional tuning, suggesting that changes in cell discharge between arm orientations cannot be explained by random temporal variations in cell activity. The distribution of movement-related preferred directions of the whole sample differed between arm orientations, and also differed strongly between cells receiving passive input predominantly from the shoulder or elbow. The electromyographic activity of most prime mover muscles at the shoulder and elbow was also strongly affected by arm orientation, resulting in changes in overall level of activity and/or directional tuning that often resembled those of the proximal arm-related motor cortical cells. A mathematical model that represented movements in terms of movement direction centered on the hand could not account for any of the arm-orientation-related response changes seen in this task, whereas models in intrinsic parameter spaces of joint kinematics and joint torques predicted many of the effects.     

Differences between chimpanzees (Pan troglodytes) and humans (Homo sapiens) in the resting state of the index finger: Implications for pointing.

Pointing with the index finger is a universal human (Homo sapiens) behavior found in cultures around the world. The emergence of pointing in infancy has traditionally been linked with the early development of cognitive capacities such as perspective-taking, intersubjectivity, and empathy. In contrast to humans, chimpanzees (Pan troglodytes) do not develop a pointing gesture with the index finger and rarely point by gesturing with hands or arms. However, recent experimental data suggest that chimpanzees may develop cognitive skills related to perspective-taking and empathy. In this article we report the existence of a difference in the resting morphology of the index finger in humans and chimpanzees. We speculate on how this species difference may be related to species differences in pointing with the index finger. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Looking at the bright side: The affective monitoring of direction.

The monitoring of internal functioning and information processing can evoke affect, even when only affectively neutral stimuli are processed. Smooth functioning induces positive affect, whereas difficulties and interruptions lead to negative affect. In 2 studies, the authors investigated explicit and implicit affect induced by simple arrows pointing to either the left or the right. The authors expected that attentional shifts due to the arrows would be performed more easily in the reading direction, and lead to more positive affect, than shifts in the opposite direction. In Experiment 1, Dutch left-to-right readers subjectively rated arrows to the right much more positively than arrows to the left. In Experiment 2, an arrow pointing right speeded arm flexion (i.e., approach), whereas an arrow pointing left facilitated arm extension (i.e., avoidance), indicating strong implicit affective influences of the arrows. If affective monitoring indeed represents a basic mechanism for implicit affect elicitation, affect no longer needs to be analyzed exclusively in terms of conscious experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of pointing as a social gesture.

Determined the age at which infants call interesting objects to another's attention by pointing, related their ability to follow another's pointing to their own use of the gesture, and compared the uses of pointing and reaching. 48 Ss aged 10–16 mo were studied with their mothers in a setting containing 6 special stimulus objects. By 12.5 mo, most Ss pointed, usually vocalizing or looking at their partner while pointing. The communicative function of the gesture was further established by the partner's response of verbal acknowledgment and looking at the object. The ability to follow another's points seemed to be acquired before Ss began to point but improved with their own use of the gesture. Reaching partook of the behaviors associated with pointing but developed earlier and decreased as pointing increased. Data show that at an early age Ss exhibit an elementary form of the ability to take the visual perspective of others. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cortical populations and behaviour: Hebb's thread.

This paper discusses work on the function of the motor cortex as revealed by single cell recordings in monkeys and artificial neural network modelling. Our key conceptual approach both in behavioural neuroscience and neural network modeling of motor cortical function relies on reconstructing, visualizing, and modelling the activity in neuronal populations, indeed a key concept advanced by D. O. Hebb (1949). The behaviour investigated ranges from exertion of isometric force to pointing movements to complex cognitive processing. The functional properties of single cells with respect to the direction of movement in space are described as well as a population code which provides a unique measure for this direction. Finally, the results of modeling studies are discussed in which directional population activity is used as an input to an artificial neural network to drive a simulated arm. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Making children gesture brings out implicit knowledge and leads to learning.

Speakers routinely gesture with their hands when they talk, and those gestures often convey information not found anywhere in their speech. This information is typically not consciously accessible, yet it provides an early sign that the speaker is ready to learn a particular task (S. Goldin-Meadow, 2003). In this sense, the unwitting gestures that speakers produce reveal their implicit knowledge. But what if a learner was forced to gesture? Would those elicited gestures also reveal implicit knowledge and, in so doing, enhance learning? To address these questions, the authors told children to gesture while explaining their solutions to novel math problems and examined the effect of this manipulation on the expression of implicit knowledge in gesture and on learning. The authors found that, when told to gesture, children who were unable to solve the math problems often added new and correct problem-solving strategies, expressed only in gesture, to their repertoires. The authors also found that when these children were given instruction on the math problems later, they were more likely to succeed on the problems than children told not to gesture. Telling children to gesture thus encourages them to convey previously unexpressed, implicit ideas, which, in turn, makes them receptive to instruction that leads to learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)