Horst Krist

Intuitive physics in action and judgment: The development of knowledge about projectile motion.

This article contrasts intuitive knowledge about projectile motion expressed in action with knowledge expressed in explicit judgments. In the action condition of Experiment 1 children and adults threw a ball horizontally from different heights to hit targets on the floor; in the judgment condition the same subjects rated the respective launch speeds required. All age groups appropriately varied the launch speed with respect to both height of release and target distance in the action condition. In the judgment condition, however, kindergartners failed to integrate the relevant dimensions and even fourth graders and adults showed misconceptions of the speed-height relation. Experiment 2 established that the speed gradations in the action condition did not critically depend on visual flight feedback or the availability of outcome information

When is the ball going to hit the ground? Duration estimates, eye movements, and mental imagery of object motion.

Performance in 2 versions of a computer-animated task was compared. Participants either indicated the time of arrival of a target that rolled off a horizontal surface and fell--hidden from view--onto a landing point (production task) or judged flight time on a rating scale (judgment task). As predicted, performance was significantly better in the production task (Experiment 1), in which imagery of object motion probably replaced reasoning processes. Participants who exhibited eye movements suggesting mental tracking performed particularly well in the production task (Experiment 2). There was, however, no decrement in performance when participants were asked to fixate the point where the target disappeared. For motion duration estimations, eye movements seem to be only a by-product of mental tracking.

Development of naive beliefs about moving objects: The straight-down belief in action

Abstract The naive belief that carried objects fall straight down when released has become known as the straight-down belief in the literature of intuitive physics. The present data show that, without formal instruction, many children revise the straight-down belief between 8 and 12 years of age. In Experiment 1, 6-, 8-, and 12-year-old children repeatedly tried to hit a target on the floor or on a table (without feedback) by dropping a ball while moving and judged the optimal release points. Whereas, in their judgments, the majority of the 6- and 8-year-old children exhibited the erroneous straight-down belief, most 12-year-olds gave correct forward answers. In their actions, children who held the straight-down belief dropped the ball significantly later than children who exhibited correct judgmental knowledge. The results of three additional experiments provide converging evidence for the claim that children use their naive beliefs to plan their actions. The data further suggest that the straight-down belief does not directly stem from a perceptual illusion. Age differences concerning the ability to execute action plans as intended are documented and discussed in relation to conceptual development.

Judgment and action knowledge in speed adjustment tasks: experiments in a virtual environment

Two experiments were conducted to investigate childrens and adults’ knowledge of time and speed in action and judgment tasks. Participants had to set the speed of a moving car to a new speed so that it would reach a target line at the same time as a reference car moving at a higher speed and disappearing in a tunnel at the midway point. In Experiment 1 (24 10-year-olds, 24 adults), childrens and adults’ speed adjustments followed the normative pattern when responses had to be graded linearly as a function of the cars initial speed. In a non-linear condition, only adults’ action responses corresponded with the normative function. Simplifying the task by shortening the tunnel systematically in Experiment 2 (24 10-year-olds, 24 adults) enabled children to grade the speeds adequately in the action conditions only. Adults now produced normative response patterns in both judgment and action. Whether people show linearization biases was thus shown to depend on the interaction of age, task demands and response mode.

Task-Specific Knowledge of the Law of Pendulum Motion in Children and Adults

The present experiment investigated children and adults’ knowledge of the pendulum law under different task conditions. The question asked was whether adults and fourth-graders knew that the period of a pendulum is a function of pendulum length but is independent of its mass. The task was to judge the period on a rating scale (judgment task), to imagine the swinging pendulum and indicate the corresponding time interval (imagery task), or to adjust the period of a dynamically presented pendulum (perception task). Normative consideration of pendulum length as the only relevant factor was primarily found in the perception task and, for adults, in the imagery task, whereas in the judgment task, children and adults frequently considered the irrelevant dimension of mass. Most children showed poor imagery performance. Preceding adjustment (perception task) and rating (judgment task) had no differential influence on subsequent imagery performance.

Development of intuitions about support beyond infancy.

In a series of 3 experiments modeled after infant studies, 3- to- 6-year-old childrens intuitive knowledge about support was assessed. Different objects were shown either sufficiently supported or not. Children had to predict whether a block would remain standing on a platform upon release or make perceptual judgments about the possibility of a shown block-on-platform configuration. Overall, performance was strongly age-related and independent of task context. Sensitivity for the amount of contact between object and support was clearly evidenced for each of the age-groups tested and was almost perfect in 5- and 6-year-olds. By contrast, sensitivity for the proportion of an objects volume positioned over the support was only marginally reliable in 3-year-olds and still far from perfect in 6-year-olds. It is concluded that basic intuitions about support undergo distinct developmental change beyond infancy and are not yet fully developed in kindergartners.

Controlling reaching movements with predictable and unpredictable target motion in 10-year-old children and adults.

We investigated interception behavior in adults and 10-year-old children. Participants had to intercept virtual targets moving on either a predictable (linear) or unpredictable (non-linear) path (with random direction changes). Targets moved at two different velocities, which varied randomly from trial to trial. Participants reached for the targets via a force-feedback device. Reaching movements for linearly moving targets in a block of linearly moving targets were compared with reaching movements for linearly moving targets in the context of non-linearly moving targets. Movement direction and maximum speed of the first sub-movement were analyzed as well as frequency of target hits and number of sub-movements. Unpredictable target motion caused faster movement speeds than predictable target motion for both children and adults. Additionally, unpredictable target motion caused children and adults to gear their initial movement direction further towards the current position of the target, while with predictable target motion, they geared their initial movement direction further ahead of the target towards an anticipated interception position. Together, these results suggest differential processing of predictable and unpredictable object behavior in an interception task, and that this differential processing is already in place in 10-year-olds.

Children’s Block Balancing Revisited: No Evidence for Representational Redescription

According to the theory of representational redescription (RR theory, Karmiloff-Smith, 1992), children’s reasoning is grounded on implicit knowledge. This initial knowledge is first consolidated and then subjected to reiterative cycles of representational redescription, leading to knowledge of increasing accessibility. As one important piece of evidence supporting RR theory a U-shaped developmental trend regarding children’s ability to balance asymmetrical blocks has been reported. To assess whether this trend is a robust phenomenon, we investigated how 4-, 5-, 6-, and 8-year-olds (N = 65) attempted to balance symmetrical and asymmetrical blocks on a narrow support. Independent from block type, we found quasi-linear improvements with age in all performance measures. These results question the robustness of the U-shaped developmental trend regarding children’s block balancing and fail to provide any evidence for representational redescription.

Knowing How to Project Objects: Probing the Generality of Children's Action Knowledge

Previous work on the development of intuitive knowledge about trajectories has shown a dissociation between young childrens aimed throwing actions, in which they are highly sensitive to the physical laws of motion, and their explicit judgments, in which they exhibit misconceptions. This research investigated the generality of childrens action knowledge by having the participants project a ball with a sling. Instead of adjusting sling stretch, and hence sling force, correctly as a function of both the release height and the target distance, 5- and 6-year-olds (Experiment 1, N = 32) and, without flight feedback, even most 7- to 10-year-olds (Experiment 2, N = 96) considered distance only and ignored the height dimension. Similarly, childrens judgments of the required sling stretch tended to follow a distance-only rule, especially with children younger than 9 years of age. These results show that young childrens action knowledge exhibited in throwing does not generalize to arbitrary means of force production. They further suggest that there is no developmental trend toward such generalization in the age range examined.

Verknüpfung von Vorstellung und Motorik in der Entwicklung

Zusammenfassung. In einem Reaktionszeitexperiment zur mentalen Rotation von Handen, an dem 138 Kindergartenkinder, 82 Grundschuler (2. Klassenstufe) und 82 Erwachsene teilnahmen, konnte ein Einfluss der motorischen Einschrankung von Handbewegungen auf die Vorstellung nachgewiesen werden. Dieser Motoreffekt war jedoch nicht in allen Altersgruppen und Bedingungen zu beobachten. Es konnte auch nicht bestatigt werden, dass er bei jungeren Kindern generell starker ausgepragt ist als bei alteren Kindern und Erwachsenen. Dafur gab es Hinweise darauf, dass die Bedingungen, unter denen ein Motoreffekt auftritt, systematisch mit dem Alter variieren. Insbesondere war bei Kindergartenkindern ein Motoreffekt nur dann zu beobachten, wenn die eigene Handstellung mit der Perspektive auf die prasentierten Hande korrespondierte.