Perceived duration as a function of pitch

It was demonstrated with 7 observers that the duration of a high frequency tone was perceived to be longer than the duration of a low frequency tone, even though the actual duration of the two tones was equal.     

The problem of the missing wavelet.

A block face was generated by dividing a drawn face into a matrix of rectangular cells and then making the brightness of each cell equal to the average of the brightnesses within the facial area circumscribed by a cell. A wavelet analysis was performed on the numbers representing the brightnesses of the cells in each row of the matrix, and from each row, the wavelet was deleted which corresponded to the fundamental or the lowest frequency sine wave of a complex wave. The appearance of the block face was not substantially altered by the deletion of the wavelet corresponding to the fundamental.     

The geometric illusion and induced differences in perceived time

Just as circle-size induces differences in the perceived extent of a line which interconnects the circles of the Baldwin illusion, it is demonstrated that circle-size induces differences in the perceived duration of a time interval which intervenes between circles of different sizes.     

Is perceptual set negatively biased?

Binocular rivalry and the Margaret Thatcher illusion were used to assess the bias, if any, of perceptual set. The data for 8 students suggest that set is negatively biased.     

Visual image analysis by square wavelets: empirical evidence supporting a theoretical agreement between wavelet analysis and receptive field organization of visual cortical neurons

It was proposed that the human visual system analyzes images into square wavelets. To test this view, comparisons were made between the perceived similarity-dissimilarity of alphabet letters and the wavelet analyses of those same letters. For the proposal to be considered tenable, the coefficients of the wavelet analysis of similar letters must be similar, and the coefficients of the wavelet analysis of dissimilar letters must be dissimilar. From a selection of 12 letters, four pairs of letters had been reported by Van der Heijden, Mathas, and Van den Roovaart as very similar, and four other pairs of letters dissimilar. Each of the 12 letters was separately depicted in 8 x 8 matrices, and the signal represented by each of the matrices was analyzed into square wavelets using a new and original procedure which yielded a single set of coefficients for each matrix. Correlations between sets of coefficients were high (r ranged from .88 to .58) for those letter pairs judged high in similarity; correlations were low (r ranged from -.02 to .29) for those letter pairs judged low in similarity. When the correlations between the coefficients of wavelets of all eight-letter pairs were compared with the judged similarity-dissimilarity of all eight-letter pairs, the linear agreement was statistically significant. Agreement was found between the neurophysiological mapping of receptive fields of visual cortical neurons and the vectors or the pattern of pluses and minuses which characterized the wavelet analysis. Furthermore, regeneration of the visual image, or the pattern of neural activity representing the image, could be described by a tree-like flow of information among visual cortical neurons which received response data from visual receptive fields, the response data being wavelet coefficients. Results indicate the analysis accurately produces reliable transformations of visual patterns and may be a process used by the visual system.     

Inhibitory interaction between channels sensitive to direction and velocity in the human visual system

Two paradigms for the study of velocity contrast have been employed. Paradigm one has focused on perceived velocity changes across a field. Paradigm two has focused on perceived velocity changes at the juncture of disparate velocities. The current experiments employ both paradigms to look at oppositely directed motion. Using paradigm two, it was determined that, with oppositely directed motion, the effect on perceived velocity could not be attributed to lateral inhibitory interaction--in contrast to earlier reports of lateral interaction when motion was in the same direction. Using paradigm one, it was determined that the effect upon perceived velocity with oppositely directed motion appeared to involve inhibition across entire fields of motion.