Testing significance of differences between two chi-squares

This paper presents a way to test the difference between twoX ²'s. The test requires evaluating the difference with respect to theT _m (x) Bessel function. Included is a table of the 5 percent and 1 percent points for the Bessel function with degrees of freedom up to 100.This investigation was supported by National Science Foundation Grant Number GE 9846.     

Frequency-selective detection at three signal amplitudes

Using the probe-signal method, frequency-response characteristics were obtained for four Os detecting signals nominally of only 1000Hz under three signal-amplitude conditions: E/N_o=10.0, 12.6, and 15.8. Detection of 1000-Hz signals decreased systematically with signal-amplitude decreases, but signals at 850 Hz and at 1150 Hz were detected at or near the chance level during all signal-amplitude conditions. From the detection performance data, the detectability was inferred for four probe-signal frequencies relative to that of 1000-Hz signals for each of the amplitude conditions. From the curvesofrelative detectability, hal[-detectability bandwidths were estimated. Neither the relative detectability curves nor the half-detectability bandwidths indicate any systematic change in the frequencyselectivebehavior of the auditory O across the signal amplitudes used.     

Classical and bayesian inference in certain latency processes

Certain aspects of point estimation are treated for two kinds of exponential latency processes. The first unitary process is represented by a simple exponential density in which the rate parameter may be viewed as an unknown constant or as a random variable. If a second, slower exponential process is grafted onto the first, there results a postulated two-component latency between stimulus and response. Moments estimators are derived for the two parameters of this latter density, and the relevance of the second parameter to decision time is emphasized.This research was supported in part by National Institutes of Health Grant MH-04439-05. The author would like to express his appreciation to James Baker of Oregon Research Institute for certain helpful comments concerning aspects of this work.     

The role of stimulation in the delay of onset of crying in the newborn infant

Crying is said to result from stimulus need. An experiment was done in which infants were stimulated during quiet periods to see if this would postpone the onset of crying. The results were positive. An alternative explanation in terms of internal temperature control is considered.     

Taming the Heathkit-Votrax speech synthesizer

Three inexpensive text-to-speech synthesizers are described, intelligibility data from a pilot experiment are reported, and software is offered that has been written to facilitate the phonemic programming of the Heathkit-Votrax synthesizer.     

Evaluating a computational model of perceptual grouping by proximity

A formal approach to the phenomenon of perceptual grouping by proximity was investigated. Grouping judgments of random dot patterns were made by the CODE algorithm (van Oeffelen & Vos, 1982) and several related algorithms, and these judgments were compared with subjects’ grouping judgments for the same stimuli. Each algorithm predicted significantly more subject judgments than would be expected by chance. The more subjects agreed on how a given dot pattern should be grouped, the more successful was the algorithms’ ability to match the judgments for that pattern. CODE predicted significantly fewer subject judgments than did some of the other algorithms, largely because of its overemphasis on the extent of interactivity among dots as they are being grouped.