Increasing task precision demands reveals that the reach and grasp remain subject to different perception-action constraints in 12-month-old human infants

The reach and grasp follow different developmental trajectories, but are often considered to have achieved nearly adult-like precision and integration by 12 months of age. This study used frame-by-frame video analysis to investigate whether increasing precision demands, by placing small reaching targets on a narrow pedestal rather than on a flat table, would influence the reach and grasp movements of 12-month-old infants in a complementary or differential fashion. The results reveal that placing the target atop a pedestal impaired the infants’s ability to direct an appropriate digit towards the small target, but did not produce a corresponding decrease in the frequency with which they used an index-thumb pincer grip to grasp the target. This was due to the fact that, although infants were more likely to contact the target with a suboptimal part of the hand in the pedestal condition, a greater proportion of these suboptimal contacts ultimately transitioned to a successful index-thumb pincer grip. Thus, increasing task precision demands impaired reach accuracy, but facilitated index-thumb grip formation, in 12-month-old infants. The differential response of the reach and grasp to the increased precision demands of the pedestal condition suggests that the two movements are not fully integrated and, when precision demands are great, remain sensitive to different perception-action constraints in 12-month-old infants.     

Gait and reach-to-grasp movements are mutually modified when performed simultaneously

Typically, prehension and gait behaviors are studied separately. However, little is known about what changes occur in these motor skills when they are combined. We investigated and characterized motor performance during combined walking and prehension at different levels of difficulty of the prehension task. Fifteen right-handed young adults were invited to walk at their self-selected pace and grasp a dowel as they walked. They also grasped the dowel in a stationary condition (upright stance). We combined conditions with/without obstacles and stable/unstable base for dowel prehension. Modifications in gait and prehension were identified when they were combined, especially for the most difficult prehension conditions. The grasping task caused an adaptation in gait because the participants preferred to adopt a more conservative strategy of increasing their dynamic stability during the approach phase and when grasping the dowel. Walking changed the prehension movement by reducing the reaching movement time, peak wrist velocity, and peak grip aperture velocity. In addition, the peak grip aperture was affected by the presence of obstacles close to the dowel. The participants adjusted their gait during the approach phase to facilitate dowel prehension, and they controlled the hand position online to adjust its configuration based on the prehension conditions.     

Development of precision grips in chimpanzees

Although chimpanzees generally grasp small objects imprecisely between the knuckle joint of the index finger and thumb, they are capable of a true precision grip, which resembles the human pincer grip. They also grip small objects between the index and middle finger. The development of these precision grips takes place over several years into adulthood and they are not frequent before 8 years of age. Precision grips and imprecise grips are equally likely to be selected for objects of small size. Thus, not only is precise prehension relatively delayed in chimpanzees but also there is lack of consistency in selecting the distal parts of the index finger for thumb opposition. This is a qualitatively different developmental pattern than occurs in human infants who systematically select precision grips for small objects by 15 months.     

The Sound of Grasp Affordances: Influence of Grasp‐Related Size of Categorized Objects on Vocalization

Previous research shows that simultaneously executed grasp and vocalization responses are faster when the precision grip is performed with the vowel [i] and the power grip is performed with the vowel [ɑ]. Research also shows that observing an object that is graspable with a precision or power grip can activate the grip congruent with the object. Given the connection between vowel articulation and grasping, this study explores whether grasp‐related size of observed objects can influence not only grasp responses but also vowel pronunciation. The participants had to categorize small and large objects into natural and manufactured categories by pronouncing the vowel [i] or [ɑ]. As predicted, [i] was produced faster when the object's grasp‐related size was congruent with the precision grip while [ɑ] was produced faster when the size was congruent with the power grip (Experiment 1). The effect was not, however, observed when the participants were presented with large objects that are not typically grasped by the power grip (Experiment 2). This study demonstrates that vowel production is systematically influenced by grasp‐related size of a viewed object, supporting the account that sensory‐motor processes related to grasp planning and representing grasp‐related properties of viewed objects interact with articulation processes. The paper discusses these findings in the context of size–sound symbolism, suggesting that mechanisms that transform size‐grasp affordances into corresponding grasp‐ and articulation‐related motor programs might provide a neural basis for size‐sound phenomena that links small objects with closed‐front vowels and large objects with open‐back vowels.     

Effects of photoaging information and UV photo on sun protection intentions and behaviours: A cross-regional comparison

The physical environment is thought to influence walking; however, daily variations in perceived environment have received little attention. The current study sought to examine if key within-person factors (i.e., implementation intentions, social support, affect and self-efficacy) would be associated with walking and if perceived access to supportive environments (e.g., access to nice walking paths) and perceived environmental barriers (e.g., bad weather and safety issues) were uniquely associated with walking after controlling for other constructs. Participants (N?=?14, 50.0% men, 78.6% White, M age?=?59.4?±?6.4) were in the intervention arm of an 8-week controlled trial promoting walking via personal digital assistants. Participants completed electronic surveys twice a day (total entries?=?804) in which they reported brisk walking levels and psychosocial and environmental factors. Multilevel modelling was used to examine within-person variations in constructs as determinants of walking. Results suggested that daily variations in implementation intentions, social support and positive affect were positively associated with walking. Further, perceived access to supportive environments, though not perceived environmental barriers, was positively associated with walking after controlling for other constructs (p?<?0.05). Future research should explore intervention components that target context-specific information about perceived access to supportive environments as part of a broader perspective on intervention development.     

SenseCam reminiscence and action recall in memory-unimpaired people

Case studies of memory-impaired individuals consistently show that reminiscing with SenseCam images enhances event recall. This exploratory study examined whether a similar benefit would occur for the consolidation of memories in memory-unimpaired people. We tested delayed recall for atypical actions observed on a lengthy walk. Participants used SenseCam, a diary, or no external memory aid while walking, followed by reminiscence with SenseCam images, diary entries, or no aid, either alone (self-reminiscence) or with the experimenter (social reminiscence). One week later, when tested without SenseCam images or diary entries, prior social reminiscence produced greater recall than self-reminiscence, but there were no differences between memory aid conditions for action free recall or action order recall. When methodological variables were controlled, there was no recall advantage for SenseCam reminiscence with memory-unimpaired participants. The case studies and present study differ in multiple ways, making direct comparisons problematic. SenseCam is a valuable aid to the memory impaired, but its mnemonic value for non-clinical populations remains to be determined.     

Classroom-based functional and adjunctive assessments: proactive approaches to intervention selection for adolescents with attention deficit hyperactivity disorder.

The present investigation evaluated the utility of classroom-based functional and adjunctive assessments of problem behaviors for 2 adolescents who met diagnostic criteria for attention deficit hyperactivity disorder (ADHD) and comorbid oppositional defiant disorder (ODD). For children with ADHD-ODD, environmental classroom variables, when systematically manipulated by teachers, were related to the occurrence and nonoccurrence of problem behaviors. Classroom interventions derived from information that was obtained during functional and adjunctive assessments and from subsequent analyses resulted in substantial reductions in problem behaviors. Teacher and student consumer satisfaction ratings indicated that the interventions were effective and feasible in the classroom setting.     

Toward Mapping Daily Challenges of Living with ADHD: Maternal and Child Perspectives Using Electronic Diaries

Attention-deficit/hyperactivity disorder (ADHD) has an impact on the family as well as the affected child. This study developed and tested an electronic diary for mapping the challenges of everyday family life in a sample of children with ADHD being treated with pharmacotherapy. Across 7 days, mothers and children (27 ADHD; 25 non-ADHD) independently reported their moods, behaviors, and social contexts every 30 min during nonschool hours. Symptomatic behaviors and negative moods were elevated in the ADHD group, combined with maternal perceptions of lower parenting effectiveness and quality of life. Differences in the contexts of maternal anger were salient, with mothers in the ADHD group more often angry when with their children and comparison mothers more often angry when not. Although mothers' diaries were more informative, children's diaries also distinguished the two groups, especially during mornings and weekends. The need for family-wide interventions, the utility of child self-reports, and the promise of electronic diaries are discussed.     

Grasping numbers: evidence for automatic influence of numerical magnitude on grip aperture

Previous research has shown that the fingers’ aperture during grasp is affected by the numerical values of numbers embedded in the grasped objects: Numerically larger digits lead to larger grip apertures than do numerically smaller digits during the initial stages of the grasp. The relationship between numerical magnitude and visuomotor control has been taken to support the idea of a common underlying neural system mediating the processing of magnitude and the computation of object size for motor control. The purpose of the present study was to test whether the effect of magnitude on motor preparation is automatic. During grasping, we asked participants to attend to the colors of the digit while ignoring numerical magnitude. The results showed that numerical magnitude affected grip aperture during the initial stages of the grasp, even when magnitude information was irrelevant to the task at hand. These findings suggest that magnitude affects grasping preparation in an automatic fashion.     

Does how I look at what you're doing depend on what I'm doing?

Previous studies showed that people proactively gaze at the target of another's action by taking advantage of their own motor representation of that action. But just how selectively is one's own motor representation implicated in another's action processing? If people observe another's action while performing a compatible or an incompatible action themselves, will this impact on their gaze behaviour? We recorded proactive eye movements while participants observed an actor grasping small or large objects. The participants' right hand either freely rested on the table or held with a suitable grip a large or a small object, respectively. Proactivity of gaze behaviour significantly decreased when participants observed the actor reaching her target with a grip that was incompatible with respect to that used by them to hold the object in their own hand. This indicates that effective observation of action may depend on what one is actually doing, being actions observed best when the suitable motor representations may be readily recruited.     

Opposite haptic and visual induction effects observed with Titchener’s ⊥

Nineteen psychology undergraduates were requested to “grasp” the lines of a computer image of Titchener’s ⊥ with a thumb and index finger pincer grip immediately after the line to be grasped had been indicated and the whole figure extinguished. The hand remained visible. Lines were of three different lengths (6.5, 7, and 7.5 cm), and ⊥s were presented at eight different orientations (rotated in steps of 45°). Lines also had to be judged longer, shorter, or equal, relative to one another. Haptically, subjects responded correctly to the ⊥s’ undivided lines, but scaled their responses to the divided ones according to the undivided ones. Categorical judgments yielded comparable psychometric functions for both kinds of lines, with a significant shift of points of subjective equality from a difference in length between lines of 9.8% to 13.5% when the divided or the undivided line was target. Haptic sensitivity, therefore, appears to be constrained by context, whereas the classical “visual illusion,” associated with Titchener’s ⊥, may be regarded a mere decisional criterion shift.     

Coming to grips with weight perception: effects of grasp configuration on perceived heaviness

We investigated how changes in grasp configuration affect perceived heaviness in a weight discrimination task in which participants compared the weights of a series of test objects with the weight of a reference object. In different experiments, we varied the width of the grasp, the number of digits employed, the angle of the grasp surface, and the size of the contact area between the digits and the object. We show that objects are perceived to be lighter when lifting with (1) a wide grip in comparison with a narrow grip, (2) five digits in comparison with two digits, and (3) a large contact area in comparison with a small contact area. However, the angle of the contact surfaces did not influence perceived weight. We suggest that changes in central motor commands associated with grasp differences may influence perceived weight, at least under some conditions.     

What do conscientious people do? Development and validation of the Behavioral Indicators of Conscientiousness (BIC)

Typical assessments of personality traits collapse behaviors, thoughts, and feelings into a single measure without distinguishing between these different manifestations. To address this lack of specification, the current study develops and validates a measure that assesses a number of broad behaviors associated with the personality trait of conscientiousness (the Behavioral Indicators of Conscientiousness; BIC). Findings suggest that the lower-order structure of conscientious behaviors is mostly similar to the lower-order structure in extant trait measures. Furthermore, a daily diary method was used to validate the BIC against frequency counts of conscientious behavior. Overall, the results identify specific behaviors that conscientious individuals tend to perform and highlight possible advantages of this approach over broad trait assessment.     

Visual objects can potentiate a grasping neural simulation which interferes with manual response execution

Previous studies on visuomotor priming have provided insufficient information to determine whether the reach-to-grasp potentiation of a non-target object produces a specific effect during response execution. In order to answer this question, subjects were instructed to reach and grasp a response device with either a power or a precision grip, depending on whether the stimulus they saw was empty or full. Stimuli consisted of containers (graspable with either a power or a precision grip), with non-graspable stimuli added as a control condition (geometrical shapes). The image of the non-target object was removed during the execution phase. Results demonstrate slower execution responses related to motor incompatibility, though conversely, no faster responses with motor compatibility. Moreover, any visuomotor priming effect required that the container be displayed during response execution. These data suggest that during response execution, motor incompatibility produces a disruptive effect likely due to competition between two cerebral events: motor control of the actual response execution and visual object reach-to-grasp neural simulation.     

Behavioral ecology meets motor behavior: choosing between walking and reaching paths

Behavioral ecology is a field in which scientists try to predict behavioral choices, typically by estimating costs of behavioral alternatives even though those costs may involve different currencies. Researchers interested in motor behavior often have similar concerns, though the connections between these two fields have been largely unnoticed. The authors pursued a study of motor behaviors involving different currencies: walking over different distances and reaching over different distances. They found that the cost of reaching was much greater than the cost of walking. They also found that walking paths took into account hand preferences. The present study extends previous research on the neglected topic of the coordination of reaching and walking and provides a simple method that can be applied in other contexts.     

Are daily fluctuations in perceived environment associated with walking?

The physical environment is thought to influence walking; however, daily variations in perceived environment have received little attention. The current study sought to examine if key within-person factors (i.e., implementation intentions, social support, affect and self-efficacy) would be associated with walking and if perceived access to supportive environments (e.g., access to nice walking paths) and perceived environmental barriers (e.g., bad weather and safety issues) were uniquely associated with walking after controlling for other constructs. Participants (N = 14, 50.0% men, 78.6% White, M age = 59.4 ± 6.4) were in the intervention arm of an 8-week controlled trial promoting walking via personal digital assistants. Participants completed electronic surveys twice a day (total entries = 804) in which they reported brisk walking levels and psychosocial and environmental factors. Multilevel modelling was used to examine within-person variations in constructs as determinants of walking. Results suggested that daily variations in implementation intentions, social support and positive affect were positively associated with walking. Further, perceived access to supportive environments, though not perceived environmental barriers, was positively associated with walking after controlling for other constructs (p < 0.05). Future research should explore intervention components that target context-specific information about perceived access to supportive environments as part of a broader perspective on intervention development.     

Unveiling a reflective diary methodology for exploring the lived experiences of stress and coping

This article unveils a diary methodology exploring accounts of ongoing experiences during the final furlong of university life and examines the role of diary keeping for gaining insights into stress and coping with performance-related and general life stressors. The focus is on thirty young people who, following a year working in industry, were in the midst of their final year of university study—undergoing coursework assessments, preparing for final examinations, making key career choices, and taking part in the whole process of job applications, assessment centres, and interviews. All were attending a course exploring theoretical and practical approaches to self-awareness and interpersonal skills development. The article shares insights regarding the use of diaries for the exploration of stress and coping from the perspective of both the researcher and the diarist.     

On the relations between action planning, object identification, and motor representations of observed actions and objects

Recent evidence suggests that viewing a static prime object (a hand grasp), can activate action representations that affect the subsequent identification of graspable target objects. The present study explored whether stronger effects on target object identification would occur when the prime object (a hand grasp) was made more action-rich and dynamic. Of additional interest was whether this type of action prime would affect the generation of motor activity normally elicited by the target object. Three experiments demonstrated that grasp observation improved the identification of grasp-congruent target objects relative to grasp-incongruent target objects. We argue from this data that identifying a graspable object includes the processing of its action-related attributes. In addition, grasp observation was shown to influence the motor activity elicited by the target object, demonstrating interplay between action-based and object-based motor coding.     

Is grasping impaired in hemispatial neglect?

Patients with right unilateral cerebral stroke, four of which showed acute hemispatial neglect, and healthy aged-matched controls were tested for their ability to grasp objects located in either right or left space at near or far distances. Reaches were performed either in free vision or without visual feedback from the hand or target object. It was found that the patient group showed normal grasp kinematics with respect to maximum grip aperture, grip orientation, and the time taken to reach the maximum grip aperture. Analysis of hand path curvature showed that control subjects produced straighter right hand reaches when vision was available compared to when it was not. The right hemisphere lesioned patients, however, showed similar levels of curvature in each of these conditions. No behavioural differences, though, could be found between right hemisphere lesioned patients with or without hemispatial neglect on either grasp parameters, path deviation or temporal kinematics.     

Grasp cueing shows obligatory attention to action goals

To understand the grounding of cognitive mechanisms in perception and action, we used a simple detection task to determine how long it takes to predict an action goal from the perception of grasp postures and whether this prediction is under strategic control. Healthy observers detected visual probes over small or large objects after seeing either a precision grip or a power grip posture. Although the posture was uninformative it induced attention shifts to the grasp-congruent object within 350 ms. When the posture predicted target appearance over the grasp-incongruent object, observers' initial strategic allocation of attention was overruled by the congruency between grasp and object. These results might help to characterize the human mirror neuron system and reveal how joint attention tunes early perceptual processes toward action prediction.