PubMed · 4778715
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G R Engel, W G Dougherty, G B Jones. 1973. Correlation and letter recognition.. https://doi.org/10.1037/h0082482
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We study neural network models of discriminating between stimuli with two similar angles, using the two-alternative forced choice (2AFC) paradigm. Two network architectures are investigated: a two-layer perceptron network and a gating network. In the two-layer network all hidden units contribute to the decision at all angles, while in the other architecture the gating units select, for each stimulus, the appropriate hidden units that will dominate the decision. We find that both architectures can perform the task reasonably well for all angles. Perceptual learning has been modeled by training the networks to perform the task, using unsupervised Hebb learning algorithms with pairs of stimuli at fixed angles theta and delta theta. Perceptual transfer is studied by measuring the performance of the network on stimuli with theta' not equal to theta. The two-layer perceptron shows a partial transfer for angles that are within a distance a from theta, where a is the angular width of the input tuning curves. The change in performance due to learning is positive for angles close to theta, but for magnitude of theta-theta' approximately a it is negative, i.e., its performance after training is worse than before. In contrast, negative transfer can be avoided in the gating network by limiting the effects of learning to hidden units that are optimized for angles that are close to the trained angle.
New puncture and cut resistant hand protection systems have been developed to enhance the barrier to cuts and needle puncture injuries during surgical procedures. It is important, however, that these new hand protection systems do not reduce tactile sensitivity or dexterity during surgery. Consequently, it was the purpose of this report to compare the cutaneous sensibility and dexterity of physicians' hands covered by these new puncture and cut resistant hand protection systems to that of the standard surgical latex glove. The hide (Medak) portion of the Life Liner and the polyethylene (Spectra) portion of the FingGuard, which offered the greatest resistance to needle puncture, were associated with the greatest reduction in cutaneous sensibility, as determined by moving and static two-point discrimination, aesthesiometer pressure sensation, and discrimination of suture size and configuration. In addition, the physicians believed that the puncture and cut resistant Life Liner glove liner markedly interfered with their handling of surgical instruments. The ultimate benefit of these puncture and cut resistant hand protection systems must be determined in well-controlled clinical trials.
In parallel visual search, a target pattern "pops out" among distractors rapidly, requiring no effort, regardless of distractor numbers. The localization and discrimination of "pop-out" targets was investigated for this research note using similar multiple displays to those used in Sagi and Julesz's [(1985a) Science, 228, 1217-1219] and Folk and Egeth's [(1989) Journal of Experimental Psychology: Human Perception & Performance, 15, 97-110] studies. The stimulus display contained 2, 5 or 10 oblique target line segments embedded in vertical distractor lines. In the first localization task, the observer indicated whether all the targets were in other positions. The second localization task was otherwise identical to the first one, except that the number of critical inside-corner positions was four. In the discrimination task, the observer reported whether all the target lines had the same orientation, or whether one of them differed in orientation from the others. Reaction times for correct responses were measured in all three tasks. The results showed that target discrimination took place in parallel, but target localization was a "serial" process, i.e. the localization time depended on the number of targets and critical locations to be checked.