The Neurocognitive Bases of Meaningful Intransitive Gestures: A Systematic Review and Meta-analysis of Neuropsychological Studies.

Researchers and clinicians have long used meaningful intransitive (i.e., not tool-related; MFI) gestures to assess apraxia-a complex and frequent motor-cognitive disorder. Nevertheless, the neurocognitive bases of these gestures remain incompletely understood. Models of apraxia have assumed that meaningful intransitive gestures depend on either long-term memory (i.e., semantic memory and action lexicons) stored in the left hemisphere, or social cognition and the right hemisphere. This meta-analysis of 42 studies reports the performance of 2659 patients with either left or right hemisphere damage in tests of meaningful intransitive gestures, as compared to other gestures (i.e., MFT or meaningful transitive and MLI or meaningless intransitive) and cognitive tests. The key findings are as follows: (1) deficits of meaningful intransitive gestures are more frequent and severe after left than right hemisphere lesions, but they have been reported in both groups; (2) we found a transitivity effect in patients with lesions of the left hemisphere (i.e., meaningful transitive gestures more difficult than meaningful intransitive gestures) but a "reverse" transitivity effect in patients with lesions of the right hemisphere (i.e., meaningful transitive gestures easier than meaningful intransitive gestures); (3) there is a strong association between meaningful intransitive and transitive (but not meaningless) gestures; (4) isolated deficits of meaningful intransitive gestures are more frequent in cases with right than left hemisphere lesions; (5) these deficits may occur in the absence of language and semantic memory impairments; (6) meaningful intransitive gesture performance seems to vary according to the emotional content of gestures (i.e., body-centered gestures and emotional valence-intensity). These findings are partially consistent with the social cognition hypothesis. Methodological recommendations are given for future studies.

Knowing "what for," but not "where": Dissociation between functional and contextual tool knowledge in healthy individuals and patients with dementia.

OBJECTIVE: Semantic tool knowledge underlies the ability to perform activities of daily living. Models of apraxia have emphasized the role of functional knowledge about the action performed with tools (e.g., a hammer and a mallet allow a "hammering" action), and contextual knowledge informing individuals about where to find tools in the social space (e.g., a hammer and a mallet can be found in a workshop). The goal of this study was to test whether contextual or functional knowledge, would be central in the organization of tool knowledge. It was assumed that contextual knowledge would be more salient than functional knowledge for healthy controls and that patients with dementia would show impaired contextual knowledge. METHODS: We created an original, open-ended categorization task with ambiguity, in which the same familiar tools could be matched on either contextual or functional criteria. RESULTS: In our findings, healthy controls prioritized a contextual, over a functional criterion. Patients with dementia had normal visual categorization skills (as demonstrated by an original picture categorization task), yet they made less contextual, but more functional associations than healthy controls. CONCLUSION: The findings support a dissociation between functional knowledge ("what for") on the one hand, and contextual knowledge ("where") on the other hand. While functional knowledge may be distributed across semantic and action-related factors, contextual knowledge may actually be the name of higher-order social norms applied to tool knowledge. These findings may encourage researchers to test both functional and contextual knowledge to diagnose semantic deficits and to use open-ended categorization tests.

Involvement of the posterior tool processing network during explicit retrieval of action tool and semantic tool knowledge: an fMRI study.

Our ability to understand how to interact with familiar objects is supported by conceptual tool knowledge. Conceptual tool knowledge includes action tool and semantic tool knowledge which are supported by the ventro-dorsal and the ventral pathways, respectively. This apparent functional segregation has been recently called into question. In a block-design fMRI study, 35 participants were asked to complete manipulation, function, and association judgment tasks about pairs of familiar objects. Our results showed that lateral occipitotemporal cortex in the ventral pathway was more sensitive to manipulation and function judgment tasks compared with association judgment tasks. Functional connectivity analyses revealed distinct coupling patterns between inferior parietal lobule, lateral occipitotemporal cortex, and fusiform gyrus. Taken together, these data indicate that action tool and semantic tool knowledge are both supported by ventral and ventro-dorsal pathways. Moreover, the explicit retrieval of these representations is supported by the functional coupling of common and distinct brain regions of the posterior tool processing network varying according to the kind of relations to be retrieved.

Grip selection without tool knowledge: end-state comfort effect in familiar and novel tool use.

A well-known phenomenon for the study of movement planning is the end-state comfort (ESC) effect: When they reach and grasp tools, individuals tend to adopt uncomfortable initial hand postures if that allows a subsequent comfortable final posture. In the context of tool use, this effect is modulated by tool orientation, task goal, and cooperation. However, the cognitive bases of the ESC effect remain unclear. The goal of this study was to determine the contribution of semantic tool knowledge and technical reasoning to movement planning, by testing whether the ESC effect typically observed with familiar tools would also be observed with novel tools. Twenty-six participants were asked to reach and grasp familiar and novel tools under varying conditions (i.e., tool's handle downward vs. upward; tool transport vs. use; solo vs. cooperation). In our findings, the effects of tool orientation, task goal and cooperation were replicated with novel tools. It follows that semantic tool knowledge is not critical for the ESC effect to occur. In fact, we found an "habitual" effect: Participant adopted uncomfortable grips with familiar tools even when it was not necessary (i.e., to transport them), probably because of the interference of habitual movement programming with actual movement programming. A cognitive view of movement planning is proposed, according to which goal comprehension (1) may rely on semantic tool knowledge, technical reasoning, and/or social skills, (2) defines end-state configuration, which in turn (3) calibrates beginning-state comfort and hence the occurrence of the ESC effect.

The social cognitive dimension of pantomime.

Pantomime production is commonly interpreted as reflecting tool-use-related cognitive processes. Yet, in everyday life, pantomime deserves a communication function and the exaggeration of amplitude found during pantomime compared to real tool use may reflect the individual's attempt to communicate the intended gesture. Therefore, the question arises about whether pantomime is a communicative behavior that is nevertheless supported only by non-social cognitive processes. We contribute to answering this question by using kinematic analyses. Participants performed the pantomime of using a saw or a hammer from visual presentation in three conditions: Free (no specific instructions), Self (focus on the real tool-use action), and Others (focus on the communicative dimension). Finally, they used the tool with the corresponding object (Actual condition). Participants' social cognition were assessed using gold standard questionnaires. Our results indicated that the manipulation of instructions had a minor effect on the exaggeration of amplitude during pantomime. We reported a link between the social cognition score and the amplitude in the Others condition for the hammer, which suggests that social cognitive processes could take part in pantomime production in some conditions. Nevertheless, this result does not alter our conclusion that social cognitive processes might be far from necessary for pantomime production.

The visual encoding of graspable unfamiliar objects.

We explored by eye-tracking the visual encoding modalities of participants (N = 20) involved in a free-observation task in which three repetitions of ten unfamiliar graspable objects were administered. Then, we analysed the temporal allocation (t = 1500 ms) of visual-spatial attention to objects' manipulation (i.e., the part aimed at grasping the object) and functional (i.e., the part aimed at recognizing the function and identity of the object) areas. Within the first 750 ms, participants tended to shift their gaze on the functional areas while decreasing their attention on the manipulation areas. Then, participants reversed this trend, decreasing their visual-spatial attention to the functional areas while fixing the manipulation areas relatively more. Crucially, the global amount of visual-spatial attention for objects' functional areas significantly decreased as an effect of stimuli repetition while remaining stable for the manipulation areas, thus indicating stimulus familiarity effects. These findings support the action reappraisal theoretical approach, which considers object/tool processing as abilities emerging from semantic, technical/mechanical, and sensorimotor knowledge integration.

What semantic dementia tells us about the ability to infer others' communicative intentions.

As Heintz & Scott-Phillips rightly argued, pragmatics has been too commonly considered as a supplement to linguistic communication. Their aim to reorient the study of cognitive pragmatics as the foundation of many distinctive features of human behavior finds echo in the neuropsychological literature on tool use, in which the investigation of semantic dementia challenges the classical semantics versus pragmatics dissociation.

Meaningless imitation in neurodegenerative diseases: Effects of body part, bimanual imitation, asymmetry, and body midline crossing.

Visuo-imitative apraxia has been consistently reported in patients with dementia, yet there have been substantial methodological differences between studies, while multiple, sometimes competing hypotheses have been put forward to explain this syndrome. Our goals were to study specific imitation deficits in groups of patients who have been selected and assigned to a group solely based on clinical criteria. We tested the effects of body part, bimanual imitation, asymmetry of the model, and body midline crossing, in patients with cortical atrophy of the temporal lobes (semantic dementia, SD), frontal-parietal networks (FPN, i.e., posterior cortical atrophy and corticobasal syndrome) or both (Alzheimer's disease, AD). Sixty-three patients and 32 healthy controls were asked to imitate 45 meaningless finger/hand, uni-/bimanual, asymmetrical/symmetrical, and crossed/uncrossed postures. SD patients had subnormal imitation scores. FPN patients showed frequent and marked deficits in most conditions, better performance with hand than finger postures (probably because of visuo-constructive deficits), and better performance with uncrossed than crossed configurations (probably because of body schema disorganization). Bimanual configurations were difficult for AD patients, not because of bimanual activity in itself, but rather because of the complexity of the model. The finding of dissociations in 34/63 cases (54%) suggests that some patients, even within the same clinical category, can have variable performance in imitation tests as a function of the abovementioned factors. Clinicians are advised to use tests with a large array of items to properly capture patients' imitation skills. This provides a new basis for future research to unpack which neurocognitive mechanisms are disrupted to cause specific patterns of impaired imitation.

The Area Prostriata may play a role in technical reasoning.

Most recent research indicated how technical reasoning (TR), namely, a specific form of causal reasoning aimed at understanding the physical world, may support the development of tools and technologies of increasing complexity. We have recently identified the Area PF of the left inferior parietal lobe (PF) as a critical structural correlate of TR, as assessed by using two ad-hoc psycho-technical tests evaluating the two main aspects of TR, i.e., physical world's understanding and visuospatial imagery. Here, we extended our findings by implementing new ad-hoc analyses of our previous data by using a whole-brain approach. Results showed that the cortical thickness (CT) of the left Area Prostriata of the visual cortex, alongside the left Area PF CT, predicts TR performance.

Physical understanding in neurodegenerative diseases.

This quantitative review gives an overview of physical understanding (i.e., the ability to represent and use the laws of physics to interact with the physical world) impairments in Alzheimer's disease (AD), semantic dementia (SD), and corticobasal syndrome (CBS), as assessed mainly with mechanical problem-solving and tool use tests. This review shows that: (1) SD patients have apraxia of tool use because of semantic tool knowledge deficits, but normal performance in tests of physical understanding; (2) AD and CBS patients show impaired performance in mechanical problem-solving tests, probably not because of intrinsic deficits of physical understanding, but rather because of additional cognitive (AD) or motor impairments (CBS); (3) As a result, the performance in mechanical problem-solving tests is not a good predictor of familiar tool use in dementia; (4) Actual deficits of physical understanding are probably observed only in late stages of neurodegenerative diseases, and associated with functional loss.

Semantic congruency effects of prime words on tool visual exploration.

Most recent research on human tool use highlighted how people might integrate multiple sources of information through different neurocognitive systems to exploit the environment for action. This mechanism of integration is known as "action reappraisal". In the present eye-tracking study, we further tested the action reappraisal idea by devising a word-priming paradigm to investigate how semantically congruent (e.g., "nail") vs. semantically incongruent words (e.g., "jacket") that preceded the vision of tools (e.g., a hammer) may affect participants' visual exploration of them. We found an implicit modulation of participants' temporal allocation of visuospatial attention as a function of the object-word consistency. Indeed, participants tended to increase over time their fixations on tools' manipulation areas under semantically congruent conditions. Conversely, participants tended to concentrate their visual-spatial attention on tools' functional areas when inconsistent object-word pairs were presented. These results support and extend the information-integrated perspective of the action reappraisal approach. Also, these findings provide further evidence about how higher-level semantic information may influence tools' visual exploration.

Learning versus reasoning to use tools in children.

Tool behavior might be based on two strategies associated with specific cognitive mechanisms: cued-learning and technical-reasoning strategies. We aimed to explore whether these strategies coexist in young children and whether they are manifest differently through development. We presented 216 3- to 9-year-olds with a vertical maze task consisting in moving a ball from the top to the bottom of a maze. Two tool-use/mechanical actions were possible: rotating action and sliding action. Three conditions were tested, each focused on a different strategy. In the Opaque-Cue condition (cued-learning strategy), children could not see the mechanical action of each tool. Nevertheless, a cue was provided according to the tool needed to solve the problem. In the Transparent-No Cue condition (technical-reasoning strategy), no cue was presented. However, children could see the mechanical actions associated with each tool. In the Transparent-Cue condition (cued-learning and/or technical-reasoning strategies) children saw both the mechanical actions and the cues. Results indicated that the Opaque-Cue and Transparent-Cue conditions were easier than the Transparent-No-Cue condition in all children. These findings stress that children can use either cued learning or technical reasoning to use tools, according to the available information. The behavioral pattern observed in the Transparent-Cue condition suggests that children might be inclined to use technical reasoning even when the task can be solved through cued learning.

Hazardous tools: the emergence of reasoning in human tool use.

Humans are unique in the way they understand the causal relationships between the use of tools and achieving a goal. The idea at the core of the present research is that tool use can be considered as an instance of problem-solving situations supported by technical reasoning. In an eye-tracking study, we investigated the fixation patterns of participants (N = 32) looking at 3D images of thematically consistent (e.g., nail-steel hammer) and thematically inconsistent (e.g., scarf-steel hammer) object-tool pairs that could be either "hazardous" (accidentally electrified) or not. Results showed that under thematically consistent conditions, participants focused on the tool's manipulation area (e.g., the handle of a steel hammer). However, when electrified tools were present or when the visual scene was not action-prompting, regardless of the presence of electricity, the tools' functional/identity areas (e.g., the head of a steel hammer) were fixated longer than the tools' manipulation areas. These results support an integrated and reasoning-based approach to human tool use and document, for the first time, the crucial role of mechanical/semantic knowledge in tool visual exploration.

Tool acceptance and acceptability: insights from a real tool use activity.

The issue of tool adoption has been the subject of many investigations, which focus either on acceptability (evaluating intention to use, a priori) or acceptance (evaluating real tool use, a posteriori). There are many criteria in the literature explaining why a tool is accepted or rejected by users, but behavioral observations are rare. This work aims to study the relationship between acceptability and acceptance and to find out if there is a hierarchy between the criteria that lead a user to use a particular tool. We exposed participants to eight xylophones varying according to three criteria: Ease of use, Utility, and Aesthetics. We assessed acceptability and judgment of participants about xylophones with questionnaires, based on tool use observation in a video session, and after a short-term use (Experiment 1); we also measured acceptance after long-term use of five sessions during which participants learned to play xylophone (Experiment 2). The results suggested that previous exposure to the tool influenced the judgment of the user, indicating a difference between acceptability and acceptance and between observation and use of a tool. The results also indicate differences in the hierarchy of criteria. In the acceptability phase, user judgments are guided by Ease of use. However, during the acceptance phase, the Utility criterion has the greatest influence, whether in terms of tool preference, or time spent using tools.

Social learning in great white pelicans (Pelecanus onocrotalus): A preliminary study.

Great white pelicans (Pelecanus onocrotalus) exhibit life-history parameters and ecological traits thought to be associated with social learning, and advanced cognitive processing more generally. In this study we investigated whether this species can acquire novel behavior socially in a foraging context. Birds from the test group watched a trained conspecific opening an opaque box containing a food reward by using its beak, whereas the control group had no demonstrator but saw the box for an equivalent time span. Individuals from both groups were subsequently allowed access to the box. Subjects of the test group performed significantly better than the control group. This is the first experimental evidence of social learning in a cooperatively hunting bird. Further studies are needed in order to shed light on the factors favoring the evolution of this capacity, by testing different pelican species that vary in their ecology.

Effect of object substitution, spontaneous compensation and repetitive training on reaching movements in a patient with optic ataxia.

We report the case of M.B. who demonstrated severe optic ataxia with the right hand following stroke in the left hemisphere. The clinical picture may shed light on both the pathological characteristics of reaching and grasping actions, and potential rehabilitation strategies for optic ataxia. First, M.B. demonstrated a dissociation between severely impaired reaching and relatively spared grasping and tool use skills and knowledge, which confirms that grasping may be more intermingled with non-motoric cognitive mechanisms than reaching. Besides, M.B.'s reaching performance was sensitive to movement repetition. We observed a substitution effect: Reaching time decreased if M.B. repeatedly reached toward the same object but increased when object identity changed. This may imply that not only object localization but also object identity, is integrated into movement programming in reach-to-grasp tasks. Second, studying M.B.'s spontaneous compensation strategies ascertained that the mere repetition of reaching movements had a positive effect, to the point M.B. almost recovered to normal level after an intensive one-day repetitive training session. This case study seems to provide one of the first examples of optic ataxia rehabilitation. Reaching skills can be trained by repetitive training even two years post-stroke and despite the presence of visuo-imitative apraxia.

The elephant in the China shop: When technical reasoning meets cumulative technological culture.

The commentaries have both revealed the implications of and challenged our approach. In this response, we reply to these concerns, discuss why the technical-reasoning hypothesis does not minimize the role of social-learning mechanisms - nor assume that technical-reasoning skills make individuals omniscient technically - and make suggestions for overcoming the classical opposition between the cultural versus cognitive niche hypothesis of cumulative technological culture.

Tool-number interaction during a prospective memory task.

Theoretical views suggest that tool use and numerical magnitude processing can interact during prospective actions. For example, if a person intends to make a meal for several persons the next week, she/he will have to keep in mind during the homework-week large dish and large food portions for this event. Here, the magnitude 'large' can influence the future choice for large dishes and other related large tools. This study presents the first empirical evidence supporting this hypothesis. During a prospective memory task that implied to keep in mind a future action, participants were required to use a tool after processing Arabic numbers. Small (less than 5) and large (more than 5) magnitudes were employed as cues for the initiation of the tool-use task, which required participants to use inverse pliers with a small or a large object, but only for some prospective trials. The inverse pliers were used to dissociate the hand action from the tool action with the object (for example, opening the hand produced the closing action of the tool). The results revealed that during prospective trials, number processing interacted only with the tool action toward the object and not with the hand action. Specifically, after the processing of large magnitudes, the initiation of the closing action of the tool (i.e. the opening action of the hand) was reduced. This finding is discussed in the light of theories on the emergence of semantics through tool actions.

To Watch is to Work: a Review of NeuroImaging Data on Tool Use Observation Network.

Since the discovery of mirror neurons in the 1990s, many neuroimaging studies have tackled the issue of action observation with the aim of unravelling a putative homolog human system. However, these studies do not distinguish between non-tool-use versus tool-use actions, implying that a common brain network is systematically involved in the observation of any action. Here we provide evidence for a brain network dedicated to tool-use action observation, called the tool-use observation network, mostly situated in the left hemisphere, and distinct from the non-tool-use action observation network. Areas specific for tool-use action observation are the left cytoarchitectonic area PF within the left inferior parietal lobe and the left inferior frontal gyrus. The neural correlates associated with the observation of tool-use reported here offer new insights into the neurocognitive bases of action observation and tool use, as well as addressing more fundamental issues on the origins of specifically human phenomena such as cumulative technological evolution.

The elephant in the room: What matters cognitively in cumulative technological culture.

Cumulative technological culture (CTC) refers to the increase in the efficiency and complexity of tools and techniques in human populations over generations. A fascinating question is to understand the cognitive origins of this phenomenon. Because CTC is definitely a social phenomenon, most accounts have suggested a series of cognitive mechanisms oriented toward the social dimension (e.g., teaching, imitation, theory of mind, and metacognition), thereby minimizing the technical dimension and the potential influence of non-social, cognitive skills. What if we have failed to see the elephant in the room? What if social cognitive mechanisms were only catalyzing factors and not the sufficient and necessary conditions for the emergence of CTC? In this article, we offer an alternative, unified cognitive approach to this phenomenon by assuming that CTC originates in non-social cognitive skills, namely technical-reasoning skills which enable humans to develop the technical potential necessary to constantly acquire and improve technical information. This leads us to discuss how theory of mind and metacognition, in concert with technical reasoning, can help boost CTC. The cognitive approach developed here opens up promising new avenues for reinterpreting classical issues (e.g., innovation, emulation vs. imitation, social vs. asocial learning, cooperation, teaching, and overimitation) in a field that has so far been largely dominated by other disciplines, such as evolutionary biology, mathematics, anthropology, archeology, economics, and philosophy.