Direct quantitative judgments of sums and a two-stage model for psychophysical judgments

Judged magnitudes of differences between stimuli have previously been shown to support a two-stage interpretation of magnitude estimation, in which input transformations and output transformations are each describable as power functions. In an effort to provide support for the model independent of the difference estimation procedure. the present investigation employed two additional judgment tasks. We obtained magnitude judgments and category judgments of the combined magnitudes (sums) of paired weights from two groups of Ss. Values of the inferred input exponent k calculated from the two sets of data were very similar and were also remarkably similar to the exponent previously calculated from magnitude estimations of differences between weights. The output exponent calculated from magnitude judgments of sums described a concave upward function; however. the similar function describing category judgments was essentially linear. These results show that the inferred input exponent is not the result of the difference estimation task, and in addition provides support for the contention that the interval scale may be a less biased sensory measure than the magnitude scale. The introduction of an additive constant to the model improved its fit to the data but the rule by which it was introduced made very little difference.     

On the validity of scalp recordings of the auditory evoked potential

Simultaneous recording from scalp and cortical electrodes in unanesthetized and unrestrained cats revealed essentially no differences between the superficial and deep recordings of the auditory evoked responses. Human recordings taken under two conditions of muscular contraction contained no major differences from 30 to 300 msec after stimulus onset.     

Variable-interval escape from stimuli accompanied by shocks

Individual performances of three rats were examined under a procedure in which steady rates of bar pressing were maintained by conditioned aversive stimulation. Originally neutral visual and auditory stimuli were accompanied by widely and irregularly spaced pulses of shock; they were terminated on a variable-interval schedule by pressing a bar. The contingencies between behavior and shock were also duplicated in a control procedure in which no visual or auditory stimuli were provided. Pressing observed under the control procedure was attributed to differences in the aversiveness of pressing and nonpressing behavior engendered by differences in the incidence of shock following the two classes of behavior. Increased rates with visual and auditory stimuli were attributed to termination of conditioned aversive stimulation. Control rates declined more rapidly than did experimental rates as the mean interval between successive shocks was lengthened; both rates tended to decline when less than 60 sec was allowed as time out from shocks following the successful response. In the control procedure, discrimination between the continuation and discontinuation of the shock series, as measured by relative rates, depended on the relative length of the interval between shocks and the time-out period. Regular warm-up accelerations in rate were noted following an initial delay in responding at the beginning of each session. The length of time required for the warm-up depended on the length of the mean interval between shocks, indicating that exposure to a certain amount of shock was required to establish a supporting state for the observed performance.     

Regional Differences in Junior Colleges

This study examines the geographical distribution of various junior college characteristics. Scores for 6 factors or categories of college characteristics, identified in earlier ACT research, were computed for each of 581 accredited junior colleges. When these junior colleges were classified and analyzed by geographical region, significant differences were found among regions on all 6 factors—Cultural Affluence (or Private Control), Technological Specialization, Size, Age (or Conventionalism), Transfer Emphasis, and Business Orientation (or High Cost). The regional differences are discussed and implications are suggested for research and counseling as well as for junior college planning.     

Noise methods in pattern perception

This experiment investigated 4 methods of inducing visual noise at 7 levels of noise. Fortysix Ss were presented 4800 sets of 3 pattems, with the task of judging which of 2 noisy patterns was more similar to the prototype pattern. The noisy patterns were generated by adding, moving, deleting or both adding and deleting elements of the prototype. All possible comparisons of each noise method were made at each noise level and the results plotted. The results show that the various methods of introducing noise do not produce identical results, and that the similarity assessment is dependent on noise koel. Explanations are offered to account for the results.