Attention can alter the perceived contrast of a stimulus, as shown in this study. The researchers developed a psychophysical method to directly assess how attention affects the apparent contrast of visual stimuli. They found that attention increases the perceived contrast of a stimulus, indicating that attention changes the appearance of a stimulus. This finding is consistent with neurophysiological evidence suggesting that attention enhances the 'effective contrast' or salience of a stimulus. The study involved three experiments with low, high, and control contrast stimuli. In each experiment, observers were shown two Gabor patches and asked to report which one appeared higher in contrast. The results showed that when attention was directed to a stimulus, observers perceived it as having higher contrast than it actually did. This effect was observed in both low and high contrast stimuli, indicating that attention can enhance the apparent contrast of a stimulus regardless of its actual contrast level. The study also addressed methodological concerns that had previously limited the ability to determine whether attention alters appearance. The researchers controlled for potential biases by ensuring that the cues used were not informative about the stimulus's contrast or orientation. They also extended the interval between the cue and the target onset to eliminate the possibility of eye movements influencing the results. The findings suggest that attention enhances the apparent contrast of a stimulus, which may underlie the increased contrast sensitivity observed in previous psychophysical studies. This study provides direct evidence that attention can alter the appearance of a stimulus, supporting the idea that attention changes the strength of a stimulus by increasing its 'effective contrast' or salience. The results have implications for understanding how attention influences visual perception and processing.Attention can alter the perceived contrast of a stimulus, as shown in this study. The researchers developed a psychophysical method to directly assess how attention affects the apparent contrast of visual stimuli. They found that attention increases the perceived contrast of a stimulus, indicating that attention changes the appearance of a stimulus. This finding is consistent with neurophysiological evidence suggesting that attention enhances the 'effective contrast' or salience of a stimulus. The study involved three experiments with low, high, and control contrast stimuli. In each experiment, observers were shown two Gabor patches and asked to report which one appeared higher in contrast. The results showed that when attention was directed to a stimulus, observers perceived it as having higher contrast than it actually did. This effect was observed in both low and high contrast stimuli, indicating that attention can enhance the apparent contrast of a stimulus regardless of its actual contrast level. The study also addressed methodological concerns that had previously limited the ability to determine whether attention alters appearance. The researchers controlled for potential biases by ensuring that the cues used were not informative about the stimulus's contrast or orientation. They also extended the interval between the cue and the target onset to eliminate the possibility of eye movements influencing the results. The findings suggest that attention enhances the apparent contrast of a stimulus, which may underlie the increased contrast sensitivity observed in previous psychophysical studies. This study provides direct evidence that attention can alter the appearance of a stimulus, supporting the idea that attention changes the strength of a stimulus by increasing its 'effective contrast' or salience. The results have implications for understanding how attention influences visual perception and processing.