Oral speech intelligibility tests were conducted with, and without, supplementary visual observation of the speaker's facial and lip movements. The difference between these two conditions was examined as a function of the speech-to-noise ratio and of the size of the vocabulary under test. The visual contribution to oral speech intelligibility (relative to its possible contribution) is, to a first approximation, independent of the speech-to-noise ratio under test. However, since there is a much greater opportunity for the visual contribution at low speech-to-noise ratios, its absolute contribution can be exploited most profitably under these conditions.

A non-parametric analysis of recognition experiments) Abstraet A non-parametric method for evaluating the results of recognition memory experiments and psychophysical detection experiments is presented. The method is based upon an ordinal analysis of recognition performance, which transforms the results of recognition tests into equivalent results for a forced-choice experiment. Problem The standard paradigm in recognition memory experiments is that a set of stimulus items is first presented to S; these items are then intermixed with a new set of items and the combined set of items is then presented for recognition. S must identify each item as either old (0) or new (n). In a parallel manner, in psychophysical detection experiments, S's task is to identify each trial as a signal trial (s) or as a non-signal trial (ns). Suppose that under one experimental condition, S responds 0 to 90% of the old items and 1% of the new items (or responds son 90% of signal trials and on 1% of non-signal trials). Under a different condition, S responds 0 to 99% of the old and 10% of the new items (or responds s on 99% of signal trials and 10% of nonsignal trials). Which condition yields the better performance? What statistic of the data would allow us to assess changes in performance resulting from changes in experimental conditions? Conventional recognition measures, which ignore the role of n or ns responses, are inadequate. The questions are easily answered when detailed quantitative theories of behavior exist. Within the context of psychophysical detection experiments, for example, there are numerous analyses that might be used (Luce, 1963; Swets et al.,I96I). Since recognition memory experiments are formally similar to the psychophysical experiments, it is tempting to suggest that the same theories may be applied to both areas (Egan, 1958). Strong assumptions, however, must be made about the underlying mechanisms in order to make these analyses. Can meaningful quantitative speCifications of performance be achieved with weaker assumptions? Method An adequate measure of recognition performance must consider two response measures: correct acceptances (0 responses to old stimuli or s responses on signal trials) and incorrect acceptances (0 responses to new stimuli or s responses on non-signal trials). Any assumed particular combination of the two measures implies a particular theory of behavior. Until more is known about recognition, we wish to avoid specific theories.

Accounting for stimulus-specific variation in precision reveals a discrete capacity limit in visual working memory.

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Masking is typically defined in terms of the threshold change in signal level resulting from the presence of a neighboring noise. By contrast with “energetic” masking, informational masking is defined in terms of the threshold change in statistical structure resulting from the presence of a neighboring signal of the same amplitude. Forward masking, backward masking, combined masking, etc., may be defined in terms of the temporal relations of the neighboring to the informational sequences. Forward informational masking is shown to be appreciably smaller than backward or combined informational masking. The threshold change in statistical structure tends to be proportional to the ratio of the durations of the neighboring to the informational sequences.