Semantic processing in dichotic listening? A replication

This experiment explores semantic processing of one message while another is attended to and shadowed. It was an attempt to replicate and clarify an earlier finding by Lewis (1970). Like Lewis, we found that mean shadowing latency was increased when a synonym of the shadowed word coincided with it on the unattended channel. However, this occurred only with synonyms in an early list position and appeared to affect only a small proportion of trials. The implications of this and other recent findings for theories of selective listening are discussed.     

The roles of vibration amplitude and static force

Previous work (Verrillo, 1963, 1968) has shown that when measured as a change in absolute threshold, spatial summation occurs only at vibration frequencies above 40 Hz. The present study measured vibrotactile spatial summation at suprathreshold amplitudes. A matching task was used to investigate the effect of varying contactor size on sensory magnitude at three different vibration frequencies. Unlike the threshold data, increasing contactor size resulted in increases in sensory magnitude at 25 and 40 Hz as well as at 160 Hz. The amount of summation varied directly with amplitude for the two lower frequencies. In a second experiment, the effect of increasing static force, independent of contactor size, was investigated. The results indicated that the spatial summation effects noted in the first experiment may be due to increases in static force and not contactor area. The implications of these results for the concept of spatial summation and for the duplex mechanoreceptor hypothesis are discussed.     

Detection of auditory signals presented at random times: III

Reaction times to a pure tone in noise were measured. Throughout, the time from the warning signal to the reaction signal was exponentially distributed, and the signal was response terminated. Response criterion, signal intensity, and mean foreperiod wait were varied. A model that assumes a Poisson sensory transduction, a pulse-activated decision process, and an additive bounded residual process was tested. It was concluded that the assumed decision process was in error. Among the empirical results, the dependence of mean reaction time on signal waits was shown to depend largely on the average wait, not the actual one, and that this relationship between mean reaction time and average stimulus wait increased for strong signals and decreased for weak ones.     

Conditioning in the prediction of therapeutic outcome in depressions

Predictions of clinical responsiveness to tricyclic anti-depressants were studied in 25 depressed patients. A well-preserved external inhibition at the commencement of treatment was found to be the best single indicator of therapeutic success.     

A note on the calculation of weights for maximum battery reliability

Weights may be determined for combining tests so that the composite has maximum reliability, but the calculation of these weights by means of the original equations is cumbersome. It is shown that the desired weighted composite is the first principal axis of a matrix closely related to the intercorrelation matrix. Thus, simple and straightforward procedures are available for calculating the weights.