On utrocular discrimination

Observers with good stereoacuity judged which eye received sine-wave grating patterns in a two-category forced-choice procedure. Large individual differences were found, but for most observers reliable discrimination was achieved at low spatial frequencies. No observer could perform the task above chance levels at high spatial frequencies. Discrimination was unaffected by retinal location, grating orientation, grating contrast, stimulus duration, or practice with feedback. Among observers who could perform the task, the following results were obtained: (1) Introduction of high spatial frequency components did not interfere with performance so long as a low spatial frequency component was present. (2) When gratings of low equal spatial frequency were presented to both eyes simultaneously at different contrast levels, observers could identify which eye received the higher contrast. (3) At low spatial frequencies, observers could distinguish monocular from binocular presentation. (4) Temporal frequency variations (counterphase flicker) influenced performance for some observers. Binocular summation and interocular transfer were unaffected by the spatial frequency variations which modulate utrocular discrimination. A new procedure for measuring stereopsis was developed which made possible comparison of utrocular discrimination with stereopsis at specific spatial frequencies. Stereopsis appeared mildly affected by spatial frequency.     

What masks utrocular discrimination

Utrocular discrimination, the ability to judge which eye has received monocular stimulation, was studied under conditions designed to reduce the salience of the cue mediating this discrimination. In one series of experiments, these conditions involved reducing the likelihood of motor command signals, overwhelming the motor command centers, and triggering motor command signals for both eyes. Those results indicate that utrocular discrimination is not mediated by ocular movements or command signals. In a second series of experiments, a visual masking paradigrn was used. A monocular test grating appeared superimposed upon a background of binocular masking noise, which was presented either simultaneously with the target or at some interval preceding or following the target (asynchronous masking). When presented simultaneously, the binocular masking noise interfered with utrocular performance, but only when the noise contained spatial frequencies near the test frequency. Masking functions obtained under conditions of asynchronous masking indicated that the time course of the forward and backward masking changed with spatial frequency. Finally, a sustained masking pattern that was ineffective in reducing utrocular performance could be made effective by pulsing the mask simultaneously with the target. Taken together, these results implicate a transient response to the target onset as a critical factor in generating the cue for successful utrocular discrimination. This conclusion may account for the fact that utrocular discrimination falls off for normal observers as the spatial frequency of the target grating increases above 4 cycles/deg.     

Experimental and theoretical results for some models of random-dot-pattern discrimination

Summary The popular, but low-power, two-stimulus signal-detection paradigms are extended to generate response-criterion-dependent psychometric functions. Maximumlikelihood estimation within a sufficiently powerful experimental design is described, and theoretical conditions for the resulting psychometric functions to be monotonically increasing are presented. These results are applied to an experiment on the detection of spatial-density differences in briefly presented random-dot patterns. The results confirm, extend, and complement current notions put forth by H. B. Barlow and his co-workers on mechanisms of internal spatial-density representation and the efficiency of intermediate levels of visual processing.     

机会或选择

你看,朋友,我们所有的人都会遇到问题,也会渡过艰难困苦的时光。但那些积极应对和处理这些问题的人,最终在生活中获得了成功。掌握你的生活不是碰运气,而是你自己是否选择了幸福和成功。因为,人们用最好的方法使事情朝好的方向发展,就会有最好的结果。     

Chance and Counterfactuals1

Suppose the world is chancy. The worry arises that most ordinary counterfactuals are false. This paper examines David Lewis' strategy for rescuing such counterfactuals, and argues that it is highly problematic.     

Context Sensitivity and Chance

‘Chance’ is arguably a context-sensitive expression, a fact that some have thought bears upon the debate about the compatibility of determinism with objective, non-trivial chances (chances with values other than 0 or 1). In this paper, I argue that this attempted move from context sensitivity to compatibilism is misguided, for a number of reasons. First, it relies on a theory of context sensitivity that we have independent reason to reject. Second, the resulting compatibilist position leaves unanswered precisely the sorts of questions we reasonably expect a metaphysical account of chance to answer.     

Different speech-processing mechanisms can be reflected in the results of discrimination and dichotic listening tasks

The relative peakedness of diotic ABX discrimination functions for certain speech stimuli and the relative magnitude of the right ear advantage that they yield in dichotic listening tasks have been thought to be functionally parallel measures of speech processing. The results of the present study suggest that this is not always the case.     

Chance and the Continuum Hypothesis

This paper presents and defends an argument that the continuum hypothesis is false, based on considerations about objective chance and an old theorem due to Banach and Kuratowski. More specifically, I argue that the probabilistic inductive methods standardly used in science presuppose that every proposition about the outcome of a chancy process has a certain chance between 0 and 1. I also argue in favour of the standard view that chances are countably additive. Since it is possible to randomly pick out a point on a continuum, for instance using a roulette wheel or by flipping a countable infinity of fair coins, it follows, given the axioms of ZFC, that there are many different cardinalities between countable infinity and the cardinality of the continuum.     

Opportunism in Memory: Preparing for Chance Encounters

Recognizing opportunities to achieve pending goals is an important cognitive ability. But when and how do we recognize that a current situation is especially suited to resuming a past goal? The predictive encoding model suggests pending goals are encoded into memory in association with anticipated environmental features. Optimally, these features are (a) necessary for successful goal satisfaction, (b) distinctive preconditions for expecting a plan to achieve the goal, and (c) described so as to be readily identified in the environment. Later, ordinary perception of features in the environment leads to automatic recognition of opportunities already prepared in memory. Evidence from experimental studies supports this theory, and demonstrates that general preparation can produce apparently novel opportunism. These findings suggest ways to facilitate the recognition of opportunities to satisfy pending goals.