The number of ways to label a structure

It has been observed that the number of different ways in which a graph withp points can be labelled isp! divided by the number of symmetries, and that this holds regardless of the species of structure at hand. In this note, a simple group-theoretic proof is provided.This work was supported by Grant MH 10834 from the National Institute of Mental Health.     

RODS AS COLOR RECEPTORS IN SCOTOPIC VISION

With the method of successive contrast, all the principal colors have been observed when test-stimulating at levels of intensity within the photochromatic interval. Using the method of simultaneous contrast, blue and green colors have been observed within this area of intensity. It is concluded that rod activity must somehow initiate these color processes.     

Serial discrimination-reversal learning with and without errors by the California sea lion

A sea lion under water performed virtually without errors on a series of three form-discrimination reversals. Significant training requirements were the combining of a previously well-established size cue preference with the nonpreferred form cue, followed by the gradual reduction of the size cue until it was completely eliminated. Orienting responses reached a peak and then decreased during progressive-dimensional-change training, suggesting critical stages in the transition of attention from the size dimension to the form dimension. Further experimentation revealed that intensive training during these critical stages obviated the need to reduce very gradually the size cue. Without special training sea lions make perseverative errors on a series of form-discrimination reversals. "Emotional" or nontest-oriented behavior was associated only with the occurrence of successive errors.     

Binocular fusion: A test of the suppression theory

Binocular fusion may be due to interocular inhibitory suppression, an hypothesis difficult to evaluate by phenomenal inspection. A test probe method (reaction time to a light pulse) was used to measure visual sensitivity during binocular rivalry and fusion. The absence of inhibitory effects during fusion fails to support the suppression theory of fusion.     

A method for sensation scaling based on an analogy between perception and judgment

Two techniques for studying judgment are discussed. In the first of these one assumes invariance of perception over different judgment processes and conceives of the properties of one judgment process as known. Then, perceptions may be estimated under this process and utilized in the study of other judgment processes of interest. A second technique disposes of the reliance up on a basic, “known” process and instead suggests that perception be treated as free parameters to be estimated from data. The paper then proceeds to show how this second technique may be used under certain conditions on perception themselves. A concept of sensation is introduced which is thought of as generating percepts in formally the same manner as percepts are thought of as generating judgments. The idea is tried out on the perception of movement time. A simple perception process appears to give a good fit to data.     

Specificity of a cutaneous receptor

Absolute vibrotactile thresholds are determined on the human tongue and compared to corresponding data obtained on the hand. The mucosa of the tongue is devoid of Pacinian corpuscles but the hand is richly with these nerve endings. Summation of energy is characteristic of responses recorded from tissue containing Pacinian corpuscles and absent where the corpuscle is specifically sensitive to mechanical vibration.     

ADAPTATION EFFECTS AND AFTER EFFECTS OF MOVING PATTERNS VIEWED IN THE PERIPHERY OF THE VISUAL FIELD

Different patterns of figures moving behind a window were viewed by subjects while fixating a point 8.5–11° visual angle NW of the display. With prolonged viewing and small figures, the motion appeared to stop completely. With moving figures which stretched the whole way across the field, perpendicular to the direction of motion, a pulsating or wave motion was experienced. A reduction in the number of moving figures was also reported with all the patterns. When the stimulus motion was stopped, the expected after effect of motion in the opposite direction was usually experienced, although in many cases the stopping of the stimulus motion led to an immediate disappearance of the stimulus figures.     

Toolbox-based routines for Macintosh timing and display

Pascal routines are described for several real-time operations on Macintosh computers. Methods are presented for millisecond timing and for high-speed transfer of arbitrary bit-image displays to the screen. All routines are based on Toolbox procedures available on virtually all Macintosh computers.