Paul Fraisse

Visual perceptive simultaneity and masking of letters successively presented

Two sets of letters S1 and S2 when presented successively are perceived as simultaneous if the total duration of time from the beginning of S1 to the end of S2 is kert constant, whatever the duration of S1, S2, or the interval. The same law applies in the case of dots arranged to form geometrical figures. On the other hand, the phenomena of meta-contrast with letters are modified when the relative duration of S1, S2, and the interval vary. Thus perceptive integration and masking depend upon different processes.

RECOGNITION TIME MEASURED BY VERBAL REACTION TO FIGURES AND WORDS

Five Ss were required to recognise as quickly as possible four words (square, triangle, hexagon, octagon) and the four corresponding figures. Ss were acquainted with the eight stimuli, for the present experiment was preceded by one in which tachistoscopic perceptual thresholds were obtained. The stimuli were presented in random order for an unlimited time and the whole list was shown five times. Verbal reaction time was recorded by means of a vocal key. Ss median for each stimulus was calculated, and then the mean of medians for words and figures. Results are given in .O1 sec.

Le Futur Dans Les Perspectives Temporelles

Abstract In the context of the profusion of studies dealing with the future in a temporal perspective this article describes several recent works on the subject and specifies the samples investigated (in terms of age, sex, socio-cultural milieu, and personality) as well as the choice of methodology adopted which depends, on the area of inquiry explored (personal life, social interaction, planning for the future).

Parameters of visual simultaneity and of metacontrast and paracontrast of successively presented letters

Two stimuli of three consonants each were successively presented through a tachistoscope. Results show that the shorter the totr 1 duration of S1, + ISI + S2, the more often the two stimuli are perceived as simultaneous. For a given total duration, the perception of simultaneity depends on the ratio of durations S1/S2, according to a nonmonotonic function. The optimum is reached for a ratio higher than one. When the S1/S2 ratio increases from 0.25 to 4, metacontrast decreases and paracontrast increases. These two phenomena are balanced for a value of the S1/S2 ratio which corresponds to the optimum of the perception of simultaneity.

Auditory evoked potentials and the perception of rhythms.

The amplitudes of the evoked potentials (N1-P2) to successive stimuli usually decrease from the first to the second, and so on. We have studied a special case where the subject hears 4 repetitions of a simple rhythmic pattern (iamb 300-600 ms, or trochee 600-300 ms), the interval between two patterns being 1200 ms. In this case, between the reaction to the last click of a pattern and the first click of the next one, we found an increase of the N1-P2, whereas we might have expected a small decrease for this interval, which has been found by many other authors. This exception accords with the inner experience and the motor reproduction of results. In a succession of rhythmical patterns, where there are no other indices, the interval between two patterns is perceived as a pause or a ground, and is not integrated into the pattern.