The Influence of Active and Passive Motion Experience on Infants' Visual Prediction Ability.

In the present study we examined whether infants' visual prediction abilities were related to different types of motion experiences. We tested 30 6-month-old infants on a visual-spatial prediction task in which they had to visually anticipate the locational reappearance of temporarily occluded moving objects. We assigned infants to one of three experience groups: active locomotion training, passive motion experience, and a no-training control group. We tested the infants' visual prediction abilities before and after these trainings. We found improved infant predictions at a post-training test only for passively trained infants (p = .015, d = -1.033; Bonferroni corrected). Thus, we conclude that infants' visual-spatial predictions of temporally occluded moving objects was facilitated by mere movement experience, even if passive. Visual information gathered during even passive movement seemed sufficient for visual prediction.

Locomotion training contributes to 6-month-old infants' mental rotation ability.

This study investigated whether a locomotion training contributes to mental rotation performance in infants. Thirty 6-month-old pre-locomotor infants were randomly assigned to either a locomotion training or a control group which received no training. The general status of motor and cognitive development measured with the Bayley Scales did not differ between the 2 groups. Mental rotation was compared before and after the trainings using a mental rotation task in which infants were habituated to a rotating object and then tested with the same habituation object presented in a previously unseen angle and the corresponding mirror object. Results revealed that only infants in the locomotion training group showed a significant change in their looking durations at the test objects (habituation vs. mirror) in the mental rotation task. This suggests that self-produced locomotion experience can affect infants' mental rotation.

The Relationship between Crawling and Emotion Discrimination in 9- to 10-Month-Old Infants.

The present study examined whether infants' crawling experience is related to their sensitivity to fearful emotional expressions. Twenty-nine 9- to 10-month-old infants were tested in a preferential looking task, in which they were presented with different pairs of animated faces on a screen displaying a 100% happy facial expression and morphed facial expressions containing varying degrees of fear and happiness. Regardless of their crawling experiences, all infants looked longer at more fearful faces. Additionally, infants with at least 6 weeks of crawling experience needed lower levels of fearfulness in the morphs in order to detect a change from a happy to a fearful face compared to those with less crawling experience. Thus, the crawling experience seems to increase infants' sensitivity to fearfulness in faces.

Effects of visual and visual-haptic perception of material rigidity on reaching and grasping in the course of development.

The development of material property perception for grasping objects is not well explored during early childhood. Therefore, we investigated infants', 3-year-old children's, and adults' unimanual grasping behavior and reaching kinematics for objects of different rigidity using a 3D motion capture system. In Experiment 1, 11-month-old infants and for purposes of comparison adults, and in Experiment 2, 3-year old children were encouraged to lift relatively heavy objects with one of two handles differing in rigidity after visual (Condition 1) and visual-haptic exploration (Condition 2). Experiment 1 revealed that 11-months-olds, after visual object exploration, showed no significant material preference, and thus did not consider the material to facilitate grasping. After visual-haptic object exploration and when grasping the contralateral handles, infants showed an unexpected preference for the soft handles, which were harder to use to lift the object. In contrast, adults generally grasped the rigid handle exploiting their knowledge about efficient and functional grasping in both conditions. Reaching kinematics were barely affected by rigidity, but rather by condition and age. Experiment 2 revealed that 3-year-olds no longer exhibit a preference for grasping soft handles, but still no adult-like preference for rigid handles in both conditions. This suggests that material rigidity plays a minor role in infants' grasping behavior when only visual material information is available. Also, 3-year-olds seem to be on an intermediate level in the development from (1) preferring the pleasant sensation of a soft fabric, to (2) preferring the efficient rigid handle.

Children's planning of efficient tool use in a social context.

Efficient joint action requires that we anticipate situational demands both regarding our own and another person's perspective, and adapt our actions accordingly. Accordingly, when handing over a tool somebody else, it is advantageous to anticipate our future hand orientation (motor imagery), as well as the future orientation of the tool (mental rotation) relative to the other person, in order to make the transfer as smooth and efficient as possible. Furthermore, familiarity with specific tools might facilitate planning. We tested thirty-two 5.5- to 7-year-old children on a tool transfer task, asking if they consider another person's comfort when handing over different tools, and whether tool familiarity, motor imagery, and mental rotation are related to their grip choices. We compared the children's performance to that of an adult control group. Besides a rather low performance on the transfer task, we found differences in children's consideration of another person's comfort related to the specific tools they interacted with. Specifically, the unfamiliar tool (a bar) was transferred more efficiently than the familiar tools (hammer/brush). In addition, the results suggest a relation between children's consideration of another person's comfort and their mental rotation score, but no relation with their motor imagery score.

How 9-month-old crawling infants profit from visual-manual rotations in a mental rotation task.

Studies show that visual-manual object exploration influences spatial cognition, and specifically mental rotation performance in infancy. The current work with 9-month-old infants investigated which specific exploration procedures (related to crawling experience) support mental rotation performance. In two studies, we examined the effects of two different exploration procedures, manual rotation (Study 1) and haptic scanning (Study 2), on subsequent mental rotation performance. To this end, we constrained infants' exploration possibilities to only one of the respective procedures, and then tested mental rotation performance using a live experimental set-up based on the task used by Moore and Johnson (2008). Results show that, after manual rotation experience with a target object, crawling infants were able to distinguish between exploration objects and their mirror objects, while non-crawling infants were not (Study 1). Infants who were given prior experience with objects through haptic scans (Study 2) did not discriminate between objects, regardless of their crawling experience. Results indicated that a combination of manual rotations and crawling experience are valuable for building up the internal spatial representation of an object.

The positive influence of manual object exploration on predictive grasping for a moving object in 9-month-old infants.

The present study examined whether infants' manual prediction ability is related to different types of their manual object exploration behavior. Thirty-two 9-month-old infants were tested in a manual prediction task, in which they were encouraged to reach for a temporarily occluded moving object. All infants also participated in a manual exploration task, in which they could freely explore five toy blocks. Infants with a high number of haptic scans in the manual exploration task showed a higher prediction rate in the manual prediction task compared to infants with a low haptic scan score. Reaction times of all infants decreased during the test blocks. However, the reaction time of infants with a high haptic scan score was faster in general. Our findings suggest that object experiences gathered by specific manual exploratory actions, such as haptic scans, are related to infants' predictive abilities when reaching and grasping for a temporarily occluded moving object.

Training of 7-month-old infants' manual object exploration skills: Effects of active and observational experience.

In the present study, a fine motor training was developed and evaluated in which infants were trained to manually explore objects in an advanced manner. Fifty 7-month-old infants were randomly assigned to three different training conditions: (1) to an active manual exploration training, in which they learned to explore objects efficiently, (2) to an observational manual exploration training, in which they observed how an adult performed sophisticated actions on objects, or (3) to a control group receiving no training. The results impressively indicate that infants with a low level of object exploration skill prior to the training showed the most training effects as compared to infants with proficient object exploratory actions. Interestingly, this differential training effect was true for both the active and observational training, highlighting the role of social learning in infancy. Importantly, our study shows for the first time the impact of normal individual variation in infants' manual object exploration skills on the effects of a fine motor training.

The influence of grasping habits and object orientation on motor planning in children and adults.

We investigated the influence of habitual grasp strategies and object orientation on motor planning in 3-year-olds and 4- to 5-year-old children and adults. Participants were required to rotate different vertically oriented objects around 180°. Usually, adults perform this task by grasping objects with an awkward grip (thumb and index finger pointing downward) at the beginning of the movement, in order to finish it with a comfortable hand position. This pattern corresponds to the well-known end-state comfort effect (ESC) in grasp planning. The presented objects were associated with different habitual grasp orientations that either corresponded with the grasp direction required to reach end-state comfort (downward) or implied a contrary grasp orientation (upward). Additionally, they were presented either in their usual, canonical orientation (e.g., shovel with the blade oriented downward versus cup with its opening oriented upward) or upside down. As dependent variable we analyzed the number of grips conforming to the end-state comfort principle (ESC score) realized in each object type and orientation condition. The number of grips conforming to ESC strongly increased with age. In addition, the extent to which end-state comfort was considered was influenced by the actual orientation of the objects' functional parts. Thus, in all age-groups the ESC score was highest when the functional parts of the objects were oriented downward (shovel presented canonically with blade pointing downward, cup presented upside down) and corresponded to the hand orientation needed to realize ESC.

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.

The relation between crawling and 9-month-old infants' visual prediction abilities in spatial object processing.

We examined whether 9-month-old infants' visual prediction abilities in the context of spatial object processing are related to their crawling ability. A total of 33 9-month-olds were tested; half of them crawled for 7.6weeks on average. A new visual prediction paradigm was developed during which a three-dimensional three-object array was presented in a live setting. During familiarization, the object array rotated back and forth along the vertical axis. While the array was moving, two target objects of it were briefly occluded from view and uncovered again as the array changed its direction of motion. During the test phase, the entire array was rotated around 90° and then rotated back and forth along the horizontal axis. The targets remained at the same position or were moved to a modified placement. We recorded infants' eye movements directed at the dynamically covered and uncovered target locations and analyzed infants' prediction rates. All infants showed higher prediction rates at test and when the targets' placement was modified. Most importantly, the results demonstrated that crawlers had higher prediction rates during test trials as compared with non-crawlers. Our study supports the assumption that crawling experience might enhance 9-month-old infants' ability to correctly predict complex object movement.

The development of the grasp height effect as a measure of efficient action planning in children.

One effect that illustrates how people adjust aspects of their grasping according to situational constraints is the grasp height effect; when reaching for objects positioned at different heights, adults' grasp height (vertical position of the hand on the object) tends to correlate negatively with object height. This indicates that grasp positions are planned so that they facilitate later placements of the object. The current study investigated the development of the grasp height effect with 3-year-old children, 5-year-old children, and adults. This paradigm allows for studying efficient action planning in the context of a simple task with relatively low motor requirements. Other tasks used so far for studying this issue involved relatively complex adjustments of hand position that younger children might have found difficult to perform. Usually, preschoolers' performance on these tasks was relatively low. We expected that, due to the lower motor requirements of the grasp height paradigm, clearer evidence of efficient planning might be found in preschool children. A second focus of this study was to explore children's behavior in different movement phases of the grasping task. Whereas the task of placing an object at different heights involves planning, putting the object back to its original position seems to depend on recall. The results indicate a significant grasp height effect in all age groups but also significant development across the studied age range. Regarding the second movement phase, when participants were required to put the objects back on the original home shelf, 3- and 5-year-olds did not seem to act based on recall in this context.

The influence of intersensory discrepancy on visuo-haptic integration is similar in 6-year-old children and adults.

When participants are given the opportunity to simultaneously feel an object and see it through a magnifying or reducing lens, adults estimate object size to be in-between visual and haptic size. Studies with young children, however, seem to demonstrate that their estimates are dominated by a single sense. In the present study, we examined whether this age difference observed in previous studies, can be accounted for by the large discrepancy between felt and seen size in the stimuli used in those studies. In addition, we studied the processes involved in combining the visual and haptic inputs. Adults and 6-year-old children judged objects that were presented to vision, haptics or simultaneously to both senses. The seen object length was reduced or magnified by different lenses. In the condition inducing large intersensory discrepancies, children's judgments in visuo-haptic conditions were almost dominated by vision, whereas adults weighted vision just by ~40%. Neither the adults' nor the children's discrimination thresholds were predicted by models of visuo-haptic integration. With smaller discrepancies, the children's visual weight approximated that of the adults and both the children's and adults' discrimination thresholds were well predicted by an integration model, which assumes that both visual and haptic inputs contribute to each single judgment. We conclude that children integrate seemingly corresponding multisensory information in similar ways as adults do, but focus on a single sense, when information from different senses is strongly discrepant.

Object processing in visual perception and action in children and adults.

We investigated whether 6- and 7-year-olds and 9- and 10-year-olds, as well as adults, process object dimensions independent of or in interaction with one another in a perception and action task by adapting Ganel and Goodale's method for testing adults (Nature, 2003, Vol. 426, pp. 664-667). In addition, we aimed to confirm Ganel and Goodale's results in adults to reliably compare their processing strategies with those of children. Specifically, we tested the abilities of children and adults to perceptually classify (perception task) or grasp (action task) the width of a rectangular object while ignoring its length. We found that adults process object dimensions in interaction with one another in visual perception but independent of each other in action, thereby replicating Ganel and Goodale's results. Children processed object dimensions interactively in visual perception, and there was also some evidence for interactive processing in action. Possible reasons for these differences in object processing between children and adults are discussed.

Ten- and twelve-month-olds' visual anticipation of orientation and size during grasping.

The anticipation of two object dimensions during grasping was investigated in 10- and 12-month-olds. We presented objects varying in both orientation and size and analyzed infants' anticipatory hand configurations. We found in Experiment 1 that nearly all of the 12-month-olds (94%), but less than half of the 10-month-olds (40%), anticipated both dimensions before touching the object. Experiment 2 ruled out the possibility that this behavior resulted from the infants' inability to anticipate the size of the stimuli. Thus, integrating two object dimensions during reaching seems to be difficult for 10-month-olds. In addition, we found a sequential adjustment when two dimensions were considered: Infants first adjusted the orientation and then the size. The implications of our findings concerning the planning and execution of grasping movements are discussed.

Learning to grasp efficiently: the development of motor planning and the role of observational learning.

We examined whether 18-, 24-, and 42-month-old children, like adults, prospectively adjust their hand movements to insure a comfortable hand posture at the endpoint, and whether children can learn to grasp efficiently by observation. The task required grasping a bar and fitting it into a hollow cylinder in order to make it light up. Measures of quantitative (grip height), as well as qualitative (grip type) prospective grip adaptation were analyzed. Grip height adaptation was found reliably by 24 months, grip type adaptation by 3 years. The ability to learn efficient grasping by observation seems however very restricted.

The Relationship Between Processing Facial Identity and Emotional Expression in 8-Month-Old Infants.

In Experiment 1, it was investigated whether infants process facial identity and emotional expression independently or in conjunction with one another. Eight-month-old infants were habituated to two upright or two inverted faces varying in facial identity and emotional expression. Infants were tested with a habituation face, a switch face, and a novel face. In the switch faces, a new combination of identity and emotional expression was presented. The results show that infants differentiated between switch and habituation faces only in the upright condition but not in the inverted condition. Experiment 2 provides evidence that infants' nonresponse in the inverted condition can be attributed to their independent processing of facial identity and emotional expression. This suggests that infants in the upright condition processed facial identity and emotional expression in conjunction with one another.

The link between infant attention to goal-directed action and later theory of mind abilities.

Various studies have shown that infants in their first year of life are able to interpret human actions as goal-directed. It is argued that this understanding is a precondition for understanding intentional actions and attributing mental states. Moreover, some authors claim that this early action understanding is a precursor of later Theory of Mind (ToM) development. To test this, we related 6-month-olds' performance in an action interpretation task to their performance in ToM tasks at the age of 4 years. Action understanding was assessed using a modified version of the Woodward-paradigm (Woodward, 1999). At the age of 4 years, the same children were tested with the German version of the ToM scale developed by Wellman and Liu (2004). Results revealed a correlation between infants' decrement of attention to goal-directed action and their ability to solve a false belief task at the age of 4 years with no modulation by language abilities. Our results indicate a link between infant attention to goal-directed action and later theory of mind abilities.

Infant development of configural object processing in visual and visual-haptic contexts.

Infants' visual processing of objects is characterised by a developmental trend from a predominantly analytical to a configural processing mode. In two studies with 6- and 8-month-old infants, we sought to replicate this finding in a purely visual condition (inspecting objects), and to examine how far redundant visual-haptic information present in a visual-haptic condition influences the processing mode. Infants were familiarized with two objects differing in three dimensions (texture, size and shape). At test, infants were presented with a familiar object, a switch object consisting of a recombination of familiar dimensions, and a novel object, and looking times were measured. Results indicate a transition from analytical processing at 6 months to configural processing at 8 months in the visual condition. In the visual-haptic condition, both age-groups displayed configural processing. Thus, redundant visual-haptic information seems to enhance object processing.

Effects of the Ebbinghaus illusion on children's perception and grasping.

We investigated the development of the Ebbinghaus illusion in children's perception and grasping. A previous study (Hanisch et al. 2001) had reported negative illusion effects on 5- to 12-year-olds' grasping as compared to their perception. We attempted to replicate this finding and to test different hypotheses based on a direct influence of the context elements on the trajectories of the fingers which could explain this reversal of the illusion effects. For 5- to 7- and 9- to 11-year-olds we observed the classical illusion effects in perception. Illusion effects were perfectly similar for perception and grasping in 9- to 11-year-olds, while there was a non-significant trend toward smaller illusion effects in grasping for the 5- to 7-year-olds. This could be due to a slightly different effect of the illusion on younger children's grasping. However, it seems clear that there are no qualitative changes, as a reversal of the illusion effects in grasping of younger children. Finally, we show that our grasping data conform well to the motor literature for children's grasping, thereby strengthening our conclusions.