Bianca Jovanovic

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.

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.

Holistic face processing among school children, younger and older adults

While previous studies have mostly examined holistic face processing in childhood and young adulthood, the present study investigated developmental changes of holistic face processing under a lifespan perspective, including older adulthood. Children 5–7 and 9–10 years of age, as well as young and older adults were instructed to assign faces into two categories. The categories were constructed to allow either a holistic categorization according to the overall face similarities or an analytical categorization by focusing on single facial features. The results show an increase in holistic face processing from childhood to young adulthood and a decrease towards older adulthood. Features used for categorization changed from internal to external features with age. Thus, crucial changes of face processing occur beyond young adulthood.

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 Goodales method for testing adults (Nature, 2003, Vol. 426, pp. 664-667). In addition, we aimed to confirm Ganel and Goodales 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 Goodales 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.

Infant perception of the relative relevance of different manual actions

Six- to nine-month-olds have been found to perceive manual actions as object-directed. They apply this interpretation even to unfamiliar, non-purposeful-looking movements if these produce salient object-directed effects. We investigated whether infants engage in a differential weighting of movement – effect instances, perceiving some instances as more “meaningful” than others. Thus, infants might preferentially encode movement – effect couplings involving prehensile movements, in contrast to couplings involving movements like touching, even if these produce salient effects. Seven- and nine-month-olds were habituated to two movement – effect couplings in close succession, a grasp/lift event and a touch/overthrow event, each directed at one of two objects, respectively. Subsequently, one object was exchanged, and looking time to the same events, with one of them involving the novel object, was measured. Preferential encoding of the prehensile action should result in a stronger dishabituation to a change in the object involved in this action (primary object) than to a change in the object involved in the touch/overthrow event (secondary object). Nine-month-olds looked significantly longer at a primary-object change. Seven-month-olds tended to look longer at the secondary-object change. This suggests that a preferential encoding of “meaningful” as compared to salient events develops between 7 and 9 months.

Analytische und konfigurale Verarbeitung von Objekten im Säuglingsalter

Zusammenfassung. Bisherige Arbeiten haben dargelegt, dass sich innerhalb des ersten Lebensjahres ein Wechsel von einer analytischen hin zu einer konfiguralen Verarbeitung von Objekten vollzieht. Dieser Wechsel wird im Wesentlichen als von der Komplexitat der Objekte und dem Alter der Kinder abhangig gesehen. Im vorliegenden Beitrag wird untersucht, inwieweit auch spezifische Erfahrungen, die Sauglinge im Laufe der Entwicklung machen, relevant sind fur die konfigurale Verarbeitung von Objekten. In Experiment 1 wird Evidenz dafur geliefert, dass die Erfahrung 8-monatiger Sauglinge, sich selbst induziert fortzubewegen, eine relevante Bedingung fur die konfigurale Objektverarbeitung darstellt. Auserdem wird beschrieben, dass die visuelle und haptische Exploration von Objekten die konfigurale Objektverarbeitung fordert. Darauf aufbauend zeigt Experiment 2, dass 8-monatige Sauglinge die konfigurale Objektverarbeitung, die auf einer visuell-haptischen Exploration beruht, auf die pur visuelle Verarbeitung ubertra...

Visuo-haptic length judgments in children and adults

If participants simultaneously feel an object and see it through an anamorphic lens, adults judge object size to be in-between seen and felt size [1]. Young childrens judgments were, however, dominated by vision [2]. We investigated whether this age difference depends on the magnitude of the intersensory discrepancy. 6-year old children and adults judged the length of objects that were presented to vision, haptics or both senses. Lenses reduced or magnified seen length. With large intersensory discrepancies, childrens visuohaptic judgments were dominated by vision (∼90% visual weight), whereas adults weighted vision just by ∼40%. With smaller discrepancies, the childrens visual weight (∼50%) approximated that of the adults (∼35%)-and a model of multisensory integration predicted discrimination performance in both age groups. We conclude that children focus on a single sense, when information in different senses is in conflict, but can combine seemingly corresponding multisensory information in similar ways as adults do.