Infant visual acuity as a function of viewing distance.

Dynamic retinoscopy has suggested that near vision may be more acute than far vision during early infancy. To test this, acuity thresholds were determined by presenting square wave gratings in a preference paradigm to 1- and 2-month-old human infants at 4 viewing distances. Gratings were paired with unpatterned fields; direction of first fixation was the dependent measure. Infants exhibited the same acuity at each of the distances at which gratings were presented. The results were interpreted as compatible with the fact that considerable optical defocusing does not seriously affect a visual system, such as the infant's, that is sensitive only to low spatial frequencies.     

Equilibrium and duality in electromagnetic field problems

Electromagnetic fields can be treated as systems in which the field equations are the equations of equilibrium. This formulation draws the subject into the unified approach of mechanics. Close analogies to potential and kinetic energy exist and these can be used to provide double bounds to the electromagnetic energy.     

Modeling of Star-shaped and Parallel-wire Carrier Distribution Systems

It is often desirable to represent carrier distribution systems by networks so that analysis can be made to predict the behavior of these systems. Modeling of two canonical carrier distribution systems, the star-shaped system and the parallel-wire system by networks was carried out in this paper. The representation is given in terms of lumped parameters when the lengths of the carrier lines are short and it is given in terms of lumped and distributed parameters when the lengths of the carrier lines are long.     

Effects of sorting on subsequent recall of unrelated items: a developmental study.

Second graders, fifth graders, and adults participated in 2 experiments designed to study the effects of sorting on subsequent recall of unrelated words. 1 group sorted the items freely, while a second group was constrained to learn the sorting schemes generated by free subjects. In the first experiment, subjects sorted until they reached a criterion of organizational stability. In Experiment 2, sorting was terminated prior to reaching a stable criterion. Recall and output clustering were reduced in Experiment 2, relative to Experiment 1, because of organizational instability. No meaningful differences were found in either experiment in the sorting schemes generated by free subjects in the 3 age groups, nor was there an effect of age of yoking partner on performance of constrained subjects. This result differed from previous research, and it was concluded that the sorting technique diminished differences in organizational behavior usually found between older and younger subjects.     

Introductory courses in research

The purpose of this article is to describe the ways in which intending teachers in the United Kingdom are acquainted with the principles and methods of educational research. Two points must be emphasized at the outset. The first is that the discussion is intentionally limited to the content of courses of initial training; the more intensive treatment of the topics under review that can undertaken in advanced courses of in-service training is not considered. The second point to be noted is that the institutions-colleges of education and university departments of education-that are responsible for initial training in the United Kingdom are free to fashion their own curricula and methods of instruction. The absence of any central control or direction in these respects leads to a wide variety of practices and, indeed, the content of the initial training programmes in a particular college is determined, to a considerable extent, by the experience, qualifications and predilections of the members of its staff. The account that follows refers to the procedures adopted by some of the best qualified and most farsighted of those responsible for the training of teachers. Alfred Yates, formerly Senior Research Officer at the National Foundation for Educational Research, is at present Senior Tutor in the Departmen of Educational Studies at Oxford University. His educational writings includeAdmission to Grammar Schools, Grouping in Education, An Introduction to Educational Measurement (with D. A. Pidgeon), andThe Role of Research in Educational Change