General to specific development of movement patterns and memory for contingency between actions and events in young infants

To understand infants' learning of the contingency between their actions and events, we studied inter-limb movement patterns of 48 infants aged 2-4 months when they attempted moving a mobile using a string attached to their arm. The session was composed of baseline, acquisition, immediate retention test, re-acquisition, interference, and delayed retention test periods. The analysis revealed motor pattern dependence on age--infants exhibited increased movement over base line of all limbs (2-month-olds), both arms (3-month-olds), and the connected arm (4-month-olds). The acquired patterns were produced during immediate and delayed test periods across age groups. The results suggest that 2-month-olds can acquire and retain general body movements that induce contingent changes in a mobile, while 3- and 4-month-olds form memories that serve as a constraint enabling highly specific movement of their arm to effectively activate the mobile.     

Representation of plans: activation in memory

The purpose of this study is to examine the temporal representation of plans in memory. Two experiments using a priming paradigm were conducted to investigate which plans would be activated in memory when participants processed a particular plan. The 64 undergraduates who participated in Experiment 1 were asked to memorise a 1-month schedule of plans. Results showed that when participants were presented with a particular plan as a prime, the preceding plan in the schedule was immediately activated. After the activation of the preceding plan, the plan following the prime plan in the schedule was activated. Experiment 2 was conducted to examine whether the sequential effect found in Experiment 1 might be based on day order (e.g., plans for day 1, plans for day 2, etc.) or simple ordering of plans (e.g., plan 1, plan 2, etc.). However, in the results of Experiment 2, with 48 undergraduate participants, the dynamic transition in the activation of plans along the time course, seen in Experiment 1, was not observed.     

The effect of test schedules on the formation of linked perceptual classes

After training conditional discriminations among selected stimuli from two perceptual classes, the emergence of novel relations involving other members of both classes was assessed using cross-class probes. The cross-class probes were presented using one of four different testing schedules. In the 2/9 test, nine different probes were presented in each of two test blocks. In the 6/3 test, three different probes were presented in each of six test blocks. In the 18/1-RND test, each of the 18 cross-class probes was presented in separate test blocks. In the 2/9 and 6/3 tests, the cross-class probes were presented in a randomized order within test block. In the 18/1-RND test, the cross-class probes were presented in a randomized sequence. In the 18/1-PRGM test, however, the cross-class probes were presented in a programmed order (i.e., the values of the stimuli in each cross-class probe were changed systematically in the succession of probe presentations). About 55% of the linked perceptual classes emerged during the 2/9, 6/3, and 18/1-RND tests. Thus the number of different probes in a test block did not influence the emergence of classes as long as the probes were presented in a random order. Virtually all classes emerged during the 18/1-PRGM test. Thus at least one ordered introduction of different cross probes resulted in the reliable emergence of linked perceptual classes. Mechanisms responsible for linked perceptual class formation are discussed along with the relation of these classes to other complex categories.     

Perceptual organization of moving stimuli modulates the flash-lag effect

When a visual stimulus is flashed at a given location the moment a second moving stimulus arrives at the same location, observers report the flashed stimulus as spatially lagging behind the moving stimulus (the flash-lag effect). The authors investigated whether the global configuration (perceptual organization) of the moving stimulus influences the magnitude of the flash-lag effect. The results indicate that a flash presented near the leading portion of a moving stimulus lags significantly more than a flash presented near the trailing portion. This result also holds for objects consisting of several elements that group to form a unitary percept of an object in motion. The present study demonstrates a novel interaction between the global configuration of moving objects and the representation of their spatial position and may provide a new and useful tool for the study of perceptual organization.     

Nanoprecipitates of icosahedral phase in quasicrystal-strengthened Mg-Zn-Y alloys

Extensive microstructural studies have been performed with respect to the formation of the icosahedral quasicrystalline phase and its relationship to other phases in Mg 95 Zn 4.2 Y 0.8 alloy. The icosahedral phase forms as an intergranular eutectic phase as well as precipitates in the matrix. The precipitates are nanosized (typically 50 nm) with a definite orientation relationship with the matrix, sharply faceted on twofold planes which are on the basal and prismatic planes of the matrix. The detailed crystallographic relationship with the matrix is described. The icosahedral phase is occasionally found to coexist with the cubic W-Zn 3 Mg 2 Y 3 phase with a definite crystallographic relationship.     

A Developing Approach to Studying Students’ Learning through Their Mathematical Activity

We discuss an emerging program of research on a particular aspect of mathematics learning, students’ learning through their own mathematical activity as they engage in particular mathematical tasks. Prior research in mathematics education has characterized learning trajectories of students by specifying a series of conceptual steps through which students pass in the context of particular instructional approaches or learning environments. Generally missing from the literature is research that examines the process by which students progress from one of these conceptual steps to a subsequent one. We provide a conceptualization of a program of research designed to elucidate students’ learning processes and describe an emerging methodology for this work. We present data and analysis from an initial teaching experiment that illustrates the methodology and demonstrates the learning that can be fostered using the approach, the data that can be generated, and the analyses that can be done. The approach involves the use of a carefully designed sequence of mathematical tasks intended to promote particular activity that is expected to result in a new concept. Through analysis of students’ activity in the context of the task sequence, accounts of students’ learning processes are developed. Ultimately a large set of such accounts would allow for a cross-account analysis aimed at articulating mechanisms of learning.     

Dynamic Touch by Hand and Head During Walking: Protective Behavior for the Head?

We investigated perception of the extent of an object held in the hand or attached to the head during walking. Participants wielded an occluded, weighted rod by hand and by head and reported the perceived location of the rod end (relative to a virtual vertical line) while walking and while standing. There was an unexpected effect of body part on perceived location of the rod end. In particular, participants stood or walked so that the rod end was farther away from the vertical line when wielding with the head than wielding with the hand. It is possible that differences between the tasks and the relative costs of a collision influenced the locomotory behavior in each condition.     

Bantams (Gallus gallus domesticus) also perceive a reversed Zöllner illusion

Although pigeons have been shown to be susceptible to several size and length illusions, other avian species have not been tested intensively for illusory perception. Here we report how bantams perceive the Zöllner figure, in which parallel lines look nonparallel due to short crosshatches superimposed on the lines. Watanabe et al. (Cognition 119:137–141, 2011) showed that pigeons, like humans, perceived parallel lines as nonparallel but that the orientation of subjective convergence was opposite to that of humans. We trained three bantams to peck at the narrower (or wider) of the two gaps at the end of a pair of nonparallel lines. After adapting them to target lines with randomly oriented crosshatches (which result in no apparent illusion to humans), we tested the bantams’ responses on randomly inserted probe trials, in which crosshatches that should induce the standard Zöllner-like illusion for humans replaced the randomly oriented ones. The results suggested bantams, like pigeons, perceive a reversed Zöllner illusion.