The effects of stimulus dimensionality on the rate of gain of information

Hick's paradigm as extended to an absolute judgment task by Doherty was used to study the effects of dimensionality on the rate of stimulus identification in two experiments. Two undimensional conditions, size and brightness, and two bidimensional conditions, size-brightness redundant and size-brightness non-redundant, were employed. The significant linear components of the regression of choice reaction time on transmitted information for the undimensional and bidimensional stimuli supported and extended Hick's law. The finding of nearly identical slopes for the two undimensional and redundant bidimensional condition regression lines suggests a stage of processing which has a constant capacity in bits/s and which is independent of stimulus dimensionality. An increase in slope for the non-redundant condition is attributed to a difference in response requirements.

Visual feedback training in auditory localization by nursery school children

18 nursery school Ss were tested on 2 auditory localization tasks and a visual control task. After the initial test, 3 equivalent groups were formed. The groups received various auditory training procedures for several weeks, and improvements in localization were assessed periodically. Auditory training with visual confirmation produced the most improvement compared to a non-trained control group, but auditory training with no visual confirmation was also effective. The training procedures were especially effective for younger Ss. Despite large differences in localization ability at the beginning of the study, by the end the younger Ss had improved to virtually the same level as the older Ss. There was thus no evidence to suggest a qualitative difference in the perceptual integration abilities of younger and older nursery school Ss.

Perceiving real-world scenes

When a briefly presented real-world scene was jumbled, the accuracy of identifying a single, cued object was less than that when the scene was coherent. Jumbling remained an effective variable even when the subject knew where to look and what to look for. Thus an object's meaningful context may affect the course of perceptual recognition and not just peripheral scanning or memory.

On the division of attention: a disproof of the single channel hypothesis

In dichotic listening, subjects are apparently unable to attend simultaneously to two concurrent, auditory speech messages. However, in two experiments reported here, it is shown that people can attend to and repeat back continuous speech at the same time as taking in complex, unrelated visual scenes, or even while sight-reading piano music. In both cases performance with divided attention was very good, and in the case of sight-reading was as good as with undivided attention. There was little or no effect of the dual task on the accuracy of speech shadowing. These results are incompatible with the hypothesis that human attention is limited by the capacity of a general–purpose central processor in the nervous system. An alternative, “multi-channel”, hypothesis is outlined.

Serial position effects in the recall of picture sequences

Sequences of 10 pictures of familiar objects were presented for immediate recall, and typically bow-shaped serial position curves were obtained. The effects of redundant stimulus suffixes, and of redundant stimulus prefixes, which could be either extra pictures, or written words (the names of similar familiar objects) were examined. In the prefix conditions, extra words produced a general decrement over positions 1–4, as compared with a control condition. Picture prefixes had no effect. In the suffix conditions, redundant words affected positions 9 and 10, whereas the main effect of redundant pictures was at positions 8 and 9. The differential serial position effects are taken to reflect the presence of two memory codes, a verbal one and a visual one, which vary in trace-strength or accessibility at different list positions.

Auditory evoked potentials during speech perception

Neural responses evoked by the same binaural speech signal were recorded from ten right-handed subjects during two auditory identification tasks. One task required analysis of acoustic parameters important for making a linguistic distinction, while the other task required analysis of an acoustic parameter which provides no linguistic information at the phoneme level. In the time interval between stimulus onset and the subjects' identification responses, evoked potentials from the two tasks were significantly different over the left hemisphere but identical over the right hemisphere. These results indicate that different neural events occur in the left hemisphere during analysis of linguistic versus nonlinguistic parameters of the same acoustic signal.

Effects of age and mental retardation on temporal integration of visual stimuli

Investigations of the threshold for dark interval and backward masking have indicated that duration of the visual sensory trace is inversely related to MA. Based on these findings, it was predicted that lower MA Ss would fuse temporally separated halves of segmented figures at longer ISIs than higher MA Ss. Ten pairs of visual stimuli were exposed tachistoscopically so that each half of a pair would appear as meaningless segmented lines but, when fused, would be perceived as a drawing of an animal. Failure to confirm the prediction was discussed in terms of the influence of cognition on sensory threshold experiments.

Children's visual regard and manual activity in retention of information about spatial position

Pointing and visual regard were observed in 64 Ss, nursery school through second grade, to assess developmental differences in the use of overt activity to mediate position of a target moving at a constant speed. On some trials the target differed from other stimuli in the array; on some trials it was identical to other stimuli; and on the remaining trials the target was identical to other stimuli, but for short periods of time was invisible to S as it moved behind an opaque panel. Monitoring the course of the target through pointing occurred infrequently and primarily among nursery schoolers and was unrelated to correctly locating the target at the end of the trial or trial conditions. Continued visual monitoring did facilitate location of the target. However, youngest Ss failed to increase visual regard as a function of the target's similarity to other stimuli, and Ss in all but the oldest group generally had difficulty in detecting the reappearance of the target from behind the panel. The ability of the oldest children to extend the principle of a constant speed to an invisible target did not appear to be a function of an intervening stage in development in which an overt and detectable activity mediated the absent target's rate of movement.

The contribution of external and internal features to the matching of unfamiliar faces

The relative efficacy of external and internal features in matching unfamiliar faces was studied in three experiments in which the subjects matched target and test faces differing in terms of external or internal features, or both. In Experiment 1 only full congruency between target and test faces was considered a match; in Experiments 2 and 3 faces sharing the same external and internal features were also considered to be matches. A total of 100 subjects matched 192 pairs of target and test faces in a "same-different" task. Reaction times and matching errors were recorded for analyses of variance. In all three experiments performance was best when either all features matched or all features mismatched, with mismatches having a slight edge. When matches of external and internal features with the target faces were inconsistent with each other, mismatches of external features led to faster responses in Experiments 1 and 2, and mismatches of internal features led to faster responses in Experiment 3. The results suggest that since faces are configurational stimuli, face matching is influenced by the non-relevant set of features; and that mismatches, especially of external features, influence face matching more than matches do.

Comparisons of memory for nonverbal auditory and visual sequential stimuli

Properties of auditory and visual sensory memory were compared by examining subjects' recognition performance of randomly generated binary auditory sequential frequency patterns and binary visual sequential color patterns within a forced-choice paradigm. Experiment 1 demonstrated serial-position effects in auditory and visual modalities consisting of both primacy and recency effects. Experiment 2 found that retention of auditory and visual information was remarkably similar when assessed across a 10s interval. Experiments 3 and 4, taken together, showed that the recency effect in sensory memory is affected more by the type of response required (recognition vs. reproduction) than by the sensory modality employed. These studies suggest that auditory and visual sensory memory stores for nonverbal stimuli share similar properties with respect to serial-position effects and persistence over time.