Young children's ability to solve spatial problems involving a choice

When do young children become able to make an adequate choice between two alternatives based on spatial information? Children of 20, 30, and 40 months of age were either presented with two objects with different cross-sections and one aperture, or one object and two different apertures. In each trial there was one object – aperture match and the task was to find that match and insert the object. All the children understood the task and tried to solve the problems but the 20-month-olds performed randomly and not even the 40-month-olds chose all the correct correspondences consistently. The results also showed that it is easier to choose between apertures than objects. This contrasts with the ability to solve the insertion problem once the choice was made. When choosing the correct object or aperture, the 40-month-olds inserted the triangle successfully in 85% of the cases. The boys and girls were equally good at solving the task, but the boys did it faster. The results show that making a choice adds significantly to the difficulty of solving spatial problems. It requires systematic examination of the objects and apertures involved, a working memory that can handle at least three items at a time, and an ability to inhibit an incorrect choice. Such executive functions are typically found in older preschool children but the present task shows that with an appropriate setup their development can be traced from a much earlier age.     

Looming Responses to Obstacles and Apertures: The Role of Accretion and Deletion of Background Texture

Successful navigation in the world requires differentiating an obstacle in one's path from an aperture through which one could pass. An approaching obstacle is specified by texture expansion within the obstacle's contour and the deletion of background texture outside the object. In contrast, an approaching aperture contains texture expansion within the aperture's frame and accretion of background texture within the aperture's contour. This study investigated 3- to 5-month-old infants' discrimination of obstacles from apertures, examining eyeblink responses to the movement of both kinds of objects against backgrounds varying in salience. Obstacles produced stronger looming reactions than apertures, and the salience of the background influenced responses to apertures but not obstacles. These findings imply that infants differentiate obstacles from apertures based on their relative patterns of accretion versus deletion of background texture, and suggest that infants recognize the functional consequences of contact with these objects.     

Functional coupling between the limbs during bimanual reach-to-grasp movements

While it is frequently advantageous to be able to use our hands independently, many actions demand that we use our hands co-operatively. In this paper we present two experiments that examine functional binding between the limbs during the execution of bimanual reach-to-grasp movements. The first experiment examines the effect of gaze direction on unimanual and bimanual reaches. Even when subjects' eye movements are restricted during bimanual reaches so that they may only foveate one target object, the limbs remain tightly synchronized to a common movement duration. In contrast, grip aperture is independently scaled to the size of the target for each hand. The second experiment demonstrates however, that the independent scaling of grip aperture is task dependent. If the two target objects are unified so that they appear to be part of a single object, grip apertures become more similar across the hands (i.e., grip aperture to the large target object is reduced in size while peak aperture to the small target item is increased in size). These results suggest that the coupling of the limbs can operate at a functional level.     

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.     

Concurrent anticipation of two object dimensions during grasping in 10-month-old infants: A quantitative analysis

The anticipation of more than one object dimension while grasping for objects has been rarely investigated in infancy. The few existing studies by Newell et al. and Schum et al. have revealed mixed results probably mainly due to methodological limitations. Therefore, the present experiments tested concurrent anticipatory grasping for two object dimensions, namely, object size and object orientation using a quantitative motion capture system (Vicon), in 10-month-old infants and adults. We presented objects varying in size (small vs. large) and orientation (horizontally vs. vertically) and analyzed participants’ anticipatory hand configurations. As with adults, we observed that infants rotated their wrists, thumbs, and index fingers as a function of object orientation and adjusted their maximum grip apertures and their grip apertures shortly before they touched the objects as a function of object size. Analyses on an individual level showed that infants like adults anticipated both dimensions when the maximal values of aperture and angle were used but not when the measures shortly before touch were considered. Thus, the ability to anticipate more than one object dimension can already be observed at 10 months of age but seems to improve considerably over the first year of life.     

Visual Information and Object Size in the Control of Reaching

The role of vision in the control of reaching and grasping was investigated by varying the available visual information. Adults (N = 7) reached in conditions that had full visual information, visual information about the target object but not the hand or surrounding environment, and no visual information. Four different object diameters were used. The results indicated that as visual information and object size decreased, subjects used longer movement times, had slower speeds, and more asymmetrical hand-speed profiles. Subjects matched grasp aperture to object diameter, but overcompensated with larger grasp apertures when visual information was reduced. Subjects also qualitatively differed in reach kinematics when challenged with reduced visual information or smaller object size. These results emphasize the importance of vision of the target in reaching and show that subjects do not simply scale a command template with task difficulty.     

Semantic consistency versus perceptual salience in visual scenes: Findings from change detection

In a one-shot change detection task, we investigated the relationship between semantic properties (high consistency, i.e., diagnosticity, versus inconsistency with regard to gist) and perceptual properties (high versus low salience) of objects in guiding attention in visual scenes and in constructing scene representations. To produce the change an object was added or deleted in either the right or left half of coloured drawings of daily-life events. Diagnostic object deletions were more accurately detected than inconsistent ones, indicating rapid inclusion into early scene representation for the most predictable objects. Detection was faster and more accurate for high salience than for low salience changes. An advantage was found for diagnostic object changes in the high salience condition, although it was limited to additions when considering response speed. For inconsistent objects of high salience, deletions were detected faster than additions. These findings may indicate that objects are primarily selected on a perceptual basis with subsequent and supplementary effect of semantic consistency, in the sense of facilitation due to object diagnosticity or lengthening of processing time due to inconsistency.     

Is the Critical Point for Aperture Crossing Adapted to the Person-Plus-Object System?

When passing through apertures, individuals scale their actions to their shoulder width and rotate their shoulders or avoid apertures that are deemed too small for straight passage. Carrying objects wider than the body produces a person-plus-object system that individuals must account for in order to pass through apertures safely. The present study aimed to determine whether individuals scale their critical point to the widest horizontal dimension (shoulder or object width). Two responses emerged: Fast adapters adapted to the person-plus-object system by maintaining a consistent critical point regardless of whether the object was carried while slow adapters initially increased their critical point (overestimated) before adapting back to their original critical point. The results suggest that individuals can account for increases in body width by scaling actions to the size of the object width but people adapt at different rates.     

Goal-directed access to mental objects in working memory: The role of task-specific feature retrieval

In the present study, we examined the hypothesis of task-specific access to mental objects from verbal working memory. It is currently assumed that a mental object is brought into the focus of attention in working memory by a process of object selection, which provides this object for any upcoming mental operation (Oberauer, 2002). We argue that this view must be extended, since the selection of information for processing is always guided by current intentions and task goals. In our experiments, it was required that two kinds of comparison tasks be executed on digits selected from a set of three digits held in working memory. The tasks differed in regard to the object features the comparison was based on. Access to a new mental object (object switch) took consistently longer on the semantic comparison task than on the recognition task. This difference is not attributable to object selection difficulty and cannot be fully accounted for by task difficulty or differences in rehearsal processes. The results support our assumptions that (1) mental objects are selected for a given specific task and, so, are accessed with their specific task-relevant object features; (2) verbal mental objects outside the focus of attention are usually not maintained at a full feature level but are refreshed phonologically by subvocal rehearsal; and (3) if more than phonological information is required, access to mental objects involves feature retrieval processes in addition to object selection.     

Distinct Visual Cues Mediate Aperture Shaping for Grasping and Pantomime-Grasping Tasks

The authors examined whether the top-down requirements of dissociating the spatial relations between stimulus and response in a goal-directed grasping task renders the mediation of aperture trajectories via relative visual information. To address that issue, participants grasped differently sized target objects (i.e., grasping condition) and also grasped to a location that was dissociated from the target object (i.e., pantomime-grasping condition). Just noticeable difference (JND) values associated with the early through late stages of aperture shaping were computed to examine the extent to which motor output adhered to, or violated, the psychophysical principles of Weber's law. As expected, JNDs during the late stages of the grasping condition violated Weber's law: a result evincing the use of absolute visual information. In contrast, JNDs for the pantomime-grasping condition produced a continuous adherence to Weber's law. Such a result indicates that dissociating a stimulus from a response is a perception-based task and results in aperture shaping via relative visual information.     

Task requirements influence sensory integration during grasping in humans

The sensorimotor transformations necessary for generating appropriate motor commands depend on both current and previously acquired sensory information. To investigate the relative impact (or weighting) of visual and haptic information about object size during grasping movements, we let normal subjects perform a task in which, unbeknownst to the subjects, the object seen (visual object) and the object grasped (haptic object) were never the same physically. When the haptic object abruptly became larger or smaller than the visual object, subjects in the following trials automatically adapted their maximum grip aperture when reaching for the object. This adaptation was not dependent on conscious processes. We analyzed how visual and haptic information were weighted during the course of sensorimotor adaptation. The adaptation process was quicker and relied more on haptic information when the haptic objects increased in size than when they decreased in size. As such, sensory weighting seemed to be molded to avoid prehension error. We conclude from these results that the impact of a specific source of sensory information on the sensorimotor transformation is regulated to satisfy task requirements.     

The role of attention in the shift from orientation-dependent to orientation-invariant identification of disoriented objects

In two experiments, the naming of rotated line drawings of natural objects was examined after a training phase in which the objects were either attended or ignored. In the training phase of Experiment 1, subjects were presented with objects in a number of orientations over five repeated blocks of trials. In the center of each object, seven letters (Xs and Ts, colored red or blue) were presented in rapid succession. Half the subjects named aloud the rotated object and ignored the changing letter display (object-attend). The other half ignored the object and counted the number of red Ts, and then used this number to perform a simple multiplication (object-ignore). In the test phase, all subjects named the rotated objects. The results showed that in the first block of trials in the training phase, mean naming time in the object-attend condition increased the further an object was rotated from the upright. This effect of orientation for attended objects was much reduced in the later presentations of the test phase. In contrast, there was no such benefit of prior presentation observed for the naming of objects that had previously been ignored. Instead, a substantial orientation effect was shown for the naming of previously ignored objects, which was similar to the orientation effect observed for attended objects named in the first block. Similar results were found in Experiment 2, in which object-attend subjects in training covertly named the objects and then performed a letter count and multiplication task. In both experiments, performance on the letter count and multiplication task varied with the angle of the ignored object. The results suggest that full attentional resources must be allocated in order for orientation-invariant representations to be formed and used in the identification of rotated objects.     

Facilitated pointing to remembered objects in front: Evidence for egocentric retrieval or for spatial priming?

Recent spatial memory theories propose that long-term spatial memories are retrieved egocentrically. One source of evidence comes from imagined perspective taking, in which participants learn an object layout, later imagine standing at one object and facing a second (orienting) object, and then point to a third (target) object from the imagined perspective. Pointing is faster for target objects in the anterior than in the posterior half of imaginal space. This “front facilitation” is consistent with asymmetric sensory and biomechanical body properties (favoring the anterior half of body space), supporting claims of egocentric retrieval. However, front facilitation might actually result from spatial priming: Proximity differences might cause orienting objects to prime target objects more in the anterior than in the posterior half of imagined space. Using a modified perspectivetaking task that unconfounded front facilitation and spatial priming, two experiments identified separate influences of front facilitation and spatial priming when participants imagined perspectives within the surrounding environment or a remote environment.     

Priorities for representation: Task settings and object interaction both influence object memory

Following an active task, the memory representations for used and unused objects are different. However, it is not clear whether these differences arise due to prioritizing objects that are task-relevant, objects that are physically interacted with, or a combination of the two factors. The present study allowed us to tease apart the relative importance of task-relevance and physical manipulation on object memory. A paradigm was designed in which objects were either necessary to complete a task (target), moved out of the way (obstructing, but interacted with), or simply present in the environment (background). Participants’ eye movements were recorded with a portable tracker during the task, and they received a memory test on the objects after the task was completed. Results showed that manipulating an object is sufficient to change how information is extracted and retained from fixations, compared to background objects. Task-relevance provides an additional influence: information is accumulated and retained differently for manipulated target objects than manipulated obstructing objects. These findings demonstrate that object memory is influenced both by whether we physically interact with an object, and the relevance of that object to our behavioral goals.     

Organizational and spatial dynamics of attentional focusing in hierarchically structured objects

Is the focusing of visual attention object-based, space-based, both, or neither? Attentional focusing latencies in hierarchically structured compound-letter objects were examined, orthogonally manipulating global size (larger vs. smaller) and organizational complexity (two-level structure vs. three-level structure). In a dynamic focusing task, participants successively identified the global and local letters in the same trial. Overall response latencies were generally longer for larger versus smaller global objects and for three-level versus two-level object structure, indicating that attentional focusing time increases both with the magnitude of change in attentional aperture size and with the number of traversed levels of object structure. Additional experiments showed that this pattern is unique to tasks that require dynamic attentional focusing. Taken together, the results support a hierarchical object-based-spatial model of attentional focusing.     

GENERALIZATION OF OBJECT NAMING AFTER TRAINING WITH PICTURE CARDS AND WITH OBJECTS

Generalization of four retarded children's object naming responses to stimuli in the natural environment was assessed after training with either objects or pictures of the objects. Generalization was typically greater after training with objects. In a second experiment, half of the stimuli that showed little generalization were retrained by alternating the original training object with an object that belonged to the same stimulus class as the training stimulus. The other half were simply retrained using the object. The alternating procedure resulted in substantial increases in generalization to untrained objects.     

Perception of whether an object can be carried through an aperture depends on anticipated speed

We investigated whether anticipated speed of locomotion through an aperture influences perception of whether an object can be carried through that aperture. Participants reported whether they would be able to carry objects through an aperture (a) if they were to attempt to walk through the aperture and (b) if they were to attempt to run through the aperture. Furthermore, they did so when the object was held but not seen and when the object was seen but not held. In general, perception was influenced by object width and by anticipated speed but not by perceptual modality. Perceptual boundaries occurred at smaller object widths when participants anticipated running through the aperture than when they anticipated walking through the aperture. The results build on work showing that perception of affordances is influenced by kinetic potential as well as geometric properties and that perception may be supported by the detection of modality-neutral stimulation patterns.     

Attenuation of size illusion effect in dual-task conditions

We over-estimate or under-estimate the size of an object depending its background structure (e.g., the Ebbinghaus illusion). Since deciding and preparing to execute a movement is based on perception, motor performance deteriorates due to the faulty perception of information. Therefore, such cognitive process can be a source of a failure in motor performance, although we feel in control of our performance through conscious cognitive activities. If a movement execution process can avoid distraction by the illusion-deceived conscious process, the effect of the visual illusion on visuomotor performance can be eliminated or attenuated. This study investigated this hypothesis by examining two task performances developed for a target figure inducing the Ebbinghaus size illusion: showing visually perceived size of an object by index finger-thumb aperture (size-matching), and reaching out for the object and pretending to grasp it (pantomimed grasping). In these task performances, the size of the index finger-thumb aperture becomes larger or smaller than the actual size, in accordance with the illusion effect. This study examined whether the size illusion effect can be weakened or eliminated by the dual-task condition where actors’ attention to judge the object’s size and to produce the aperture size is interrupted. 16 participants performed the size-matching and pantomimed grasping tasks while simultaneously executing a choice reaction task (dual task) or without doing so (single task). Using an optical motion capture system, the size-illusion effect was analyzed in terms of the aperture size, which indicates the visually perceived object size. The illusion effect was attenuated in the dual task condition, compared to it in the single task condition. This suggests that the dual task condition modulated attention focus on the aperture movement and therefore the aperture movement was achieved with less distraction caused by illusory information.     

An advantage for active versus passive aperture-viewing in visual object recognition

In aperture viewing the field-of-view is restricted, such that only a small part of an image is visible, enforcing serial exploration of different regions of an object in order to successfully recognise it. Previous studies have used either active control or passive observation of the viewing aperture, but have not contrasted the two modes. Active viewing has previously been shown to confer an advantage in visual object recognition. We displayed objects through a small moveable aperture and tested whether people's ability to identify the images as familiar or novel objects was influenced by how the window location was controlled. Participants recognised objects faster when they actively controlled the window using their finger on a touch-screen, as opposed to passively observing the moving window. There was no difference between passively viewing again one's own window movement as generated in a previous block of trials versus viewing window movements that had been generated by other participants. These results contrast with those from comparable studies of haptic object recognition, which have found a benefit for passive over active stimulus exploration, but accord with findings of an advantage of active viewing in visual object recognition.     

Athletic experience influences shoulder rotations when running through apertures

In order to pass through apertures safely and efficiently, individuals must perceive the width of the aperture relative to (1) the width of the person-plus-object system and to (2) their (anticipated) movement speed. The present study investigated whether athletes who have extensive experience playing sports that require running through narrow spaces while wearing shoulder pads control their shoulder rotations differently while performing this behavior than athletes who lack such experience. Groups of athletes with experience competing in different sports (American football, rugby, and control athletes) performed a behavioral task in which they ran or walked between two tucking dummies with or without wearing shoulder pads. They also performed a psychophysical task in which they reported perceived width of the body and shoulder pads. When running through the apertures, the athletes who played American football exhibited smaller magnitudes and later onset of shoulder rotations than control athletes. No such difference was found when walking through the apertures. There was no difference in perception of the width of the shoulder pads among three groups. These findings suggest that performance of this behavior is action-scaled and task-specific.