中文摘要：

本研究探讨宽带宽噪音图片的＂反倾斜效应＂及短期训练对其影响。首先,我们测量被试对四个朝向（0°,45°,90°和135°）噪音图片的知觉明显度阈值。然后根据被试的阈值生成图片,让被试完成朝向辨识任务,记录正确率和反应时。结果表明人对倾斜朝向刺激的辨识显著好于主要朝向。并且,被试对所有朝向刺激的辨识经训练后都有显著提高。本研究提示人们对于这种宽带宽噪音图片的辨识能够学习,但是短期的训练不能使＂反倾斜效应＂消失。

英文摘要：

Evidence has accumulated for over a century that the visual system of humans and many other animals is more sensitive to contour stimulation at vertical or horizontal orientations than to stimulation at the oblique orientations,which is termed as an＂oblique effect＂.But this effect changes when the visual stimuli are broad-band noise images.The present study investigated the inverse oblique effect of broad-band noise stimuli and the short-term training on this effect.Broad-band noise stimuli are images with more than one orientation and spatial frequency in the frequency domain（fig.1）.First we measured the subjects＇ orientation salience thresholds with broad-band noise stimuli at four orientations（0°,45°,90°and 135°） using 3-down-1 up staircase（Experiment 1）.The subjects were asked to judge which one of the two stimulus interval consisted of an oriented image by pressing the key（fig.2）.When their responses were right for three consecutive trials,the oriented increment index which determines the oriented noise stimuli＇s orientation saliency decreased and the oriented structure of the image seemed less salient.Once their response was wrong for only one trial,the oriented increment index increased.The orientation salience thresholds were tested for 5 staircases for each of the 4 oriented stimuli and were averaged.The thresholds were corresponded to the subjects＇ 79.9%accuracy performance.Then the subjects performed an orientation identification task（Experiment 2）.The stimuli were oriented noise stimuli which were generated according to each subject s orientation salience thresholds.The four orientations of the stimuli were presented randomly and equally.The subjects had to determine the orientation of the image on the screen correctly and quickly（fig.4）.Their accuracies and reaction times were recorded. They completed 4 blocks with 40 trials per block.Then after a rest of at least one night（12 hours）,the subjects came back to continue the same experiment task.This time they c