Stimulus-specific mechanisms of visual short-term memory

The retention of spatial information in visual short-term memory was assessed by measuring spatial frequency discrimination thresholds with a two-interval forced-choice task varying the time interval between the two gratings to be compared. The memory of spatial frequency information was perfect across 10-sec interstimulus intervals. Presentation of a “memory masker” grating during the interstimulus interval may interfere with short-term memory. This interference depends on the relative spatial frequency of the test and masker gratings, with maximum interference at spatial frequency differences of 1–1.5 octaves and beyond. This range of interference with short-term memory is comparable to the bandwidth of sensory masking or adaptation. A change of the relative orientation of test and masker gratings does not produce interference with spatial frequency discrimination thresholds. These results suggest stimulus-specific interactions at higher-level representations of visual form

Getting More Farm Output per Man

We all know there are wide differences in yields per acre among different areas of Iowa. But there are differences in another type of yield that are not so apparent-yield per worker. And output per worker is a very important measure of productivity. It generally is a good indicator or how efficiently the farm production process is being carried on

Perturbation expansions for a class of singular potentials

Harrell's modified perturbation theory [Ann. Phys. 105, 379-406 (1977)] is applied and extended to obtain non-power perturbation expansions for a class of singular Hamiltonians H = -D^2 + x^2 + A/x^2 + lambda/x^alpha, (A\geq 0, alpha > 2), known as generalized spiked harmonic oscillators. The perturbation expansions developed here are valid for small values of the coupling lambda > 0, and they extend the results which Harrell obtained for the spiked harmonic oscillator A = 0. Formulas for the the excited-states are also developed.Comment: 23 page