A technique for the construction of discrete dichotic stimulation material

Procedures are described for the generation, synchronization. and accurate spacing of discrete dichotic stimulation material. A suggested standard definition of interpair interval is proposed.     

Reaction time as a function of the intensity and probability of occurrence of vibrotactile signals

Three Ss made judgments of the presence or absence of a burst of 60-cps vibration onthe index fingertip.The probability of S’s reporting the presence of a signal was found to be influenced by signal probability and signal intensity. Mean reaction time for reporting the presence of a signal decreased as a function of signal intensity and signal probability whereas mean reaction time for reporting the absence of a signal increased as a function of signal intensity and signal probability. On trials where no signal was presented mean R T for reporting a signal decreased with increases in the signal probability whereas mean RT for reporting the absence of a signal increased with increases in signal probability. The results were interpreted as support for the hypothesis that S’s decision time was longer the closer on the sensory continuum a particular observation was to his criterion.     

Prismatic displacement and the remembered location of targets

Following adaptation, only the trained limb misreaches to the remembered location of targets. This suggests a change in the feit position of the trained limb, but conflicts with recent reports, and with the hypothesis that when a limb changes, the remembered location of targets encountered only by that limb undergo some change too. It suggests that information is stored independently of the mode of acquisition.     

Effects of uncertain warning signals on reaction time

Three experiments were conducted in an attempt to assess the effectiveness of a warning signal in reducing reaction time when (1) the signal to respond (danger signal) follows the warning signal with a probability less than 1.0, and (2) the interval between warning and danger signals (W-D interval) is variable. The required response was the depression of a foot pedal, as in automobile braking. It was determined that probabilistic warning information could be effective if observers made use of the W-D interval to prepare to make the response required by the danger signal. It was noted, however, that observers differed considerably in their tendency to do this. A model was proposed for describing different response strategies.     

On the rate of stimulus occlusion during intermittent retinal stimulation

The CFF was determined with three sectored disks, each of which corresponded to one of the three rings in a Helmholtz disk. The fusion frequency is identical for all three rings of a Helmholtz disk but with the three sectored disks it was found that the rate of stimulus occlusion is a major factor in determining the CFF. It was tentatively concluded that the effect was not a consequence of different stimulus wave-forms. The phenomenon appears to have been reported late in the last century.     

Orientation of letters and errors in their recognition

Subjects named alphabetic characters that had been rotated, reflected, or inverted. Inversions induce more errors than mirror reflections and reflections induce more than rotations. In a significant number of mistakes a transformed character was assumed to be normally oriented, but in most a transformed character was confused with the mirror image of the original. The data suggest the existence of an “orientation set” in which the identiflcation of ambiguous characters depends largely on their anticipated orientation. The individuality of the data for the different orientations suggests that different transformations are compensated for in part by different mechanisms.     

Size and distance judgments under reduced conditions of viewing

Magnitude estimations of the size and distance of a variable relative to a standard were obtained in the absence of distance cues. Estimates were provided by different groups under three conditions: (a) physical size and distance variant, visual angle of the variable constant and equal to the standard, (b) physical size constant, physical distance and visual angle of variable changing, and (c) physical distance constant, physical size and visual angle of the variable changing. The results in both experiments were very similar. In each case both size and distance estimates conformed to relative visual angle. The results are applied to an analysis of size-matches that are obtained when distance cues are eliminated.     

Perception of interpolated position and orientation by vision and active touch

Vision and active touch lead to similar patterns of constant error for the perception of interpolated position in twodimensional and one-dimensional regions, though the errors for touch are larger than those for vision. The error patterns for the orientation of a radius of a semicircle are more complex, but can be interpreted as due to the interaction of two sets of anchors rather than the single pair available for the linear interpolation. The greater size of the touch errors is interpreted as due to a relative overestimation of larger distances by active touch or of smallerdistances by vision.     

Kinetic disruption of optical texture: The perception of depth at an edge

An examination of the changes in visual stimulation that result from changes in the occlusion of one surface or object by another suggests two hypotheses about the motion-carried information that is sufficient for the perception of the relative depth at an edge as well as the perception of occlusion. Ss’ reports when shown displays containing only this information give strong support to the hypotheses.