Encoding effects of remindings

Understanding requires prior knowledge. Most theories and empirical work on understanding have focused on the use of general prior knowledge. In the experiments presented here, we examined the role of specific prior episodes in understanding. Subjects read ambiguous stories that had some superficial cue to make them think back to an earlier story. Experiment 1 shows that a superficial cue to an earlier story affects how the new story is interpreted. Experiment 2, in which a reading-time measure was used, provides evidence that this effect of the earlier story occurs during the initial understanding of the new story. We discuss the implications of these results for theories of understanding and the use of remindings in analogy.     

Language lateralization to the dominant hemisphere: Tool use, gesture and language in hominid evolution

Shared tool use in our hominid ancestry is perhaps the most satisfactory explanation for human dextrality and left-hemisphere language lateralization. Recent palaeoarchaeological evidence suggests that brachiation preceded bipedalism, which in turn preceded advanced tool use, with all three preceding any dramatic increase in brain size and/or the development of speech-related neural structures. Shared tool use probably led to population dextrality, and then to the development of left-hemisphere centres for fine motor coordination and the mediation of serial, segmental, time-dependent and syntactic processes at sensory and more particularly motor levels, including the control of limbs, fingers and articulators. Such centres, initially developed for tool construction and use, would have occupied an intermediate position in the evolutionary sequence. Thus cortically-driven facial gestures may possibly have accompanied manual signing, modulating limbic vocalizations of affect, though a cortical-limbic distinction with respect to communication may be unwarranted. However, the uniqueness of human language is still a matter of debate both with respect to other primates and our own evolutionary ancestors.     

Disparity minimisation, cyclovergence, and the validity of nonius lines as a technique for measuring torsional alignment

Frisby et al (1993 Perception 22 Supplement, 115) proposed that the visual system might make cyclovergent eye movements in order to minimise the overall pattern of both vertical and horizontal disparities when an observer views an inclined stereoscopic surface. Their measurements of cyclovergence, which used vertically oriented nonius lines, were found to be consistent with that proposal. In our experiment 1, we measured torsional eye movements objectively, using scleral coils, and found no evidence of a cyclovergent response to either a real inclined surface or to a simulated inclined surface in which the two stereoscopic images were related by a horizontal shear transformation. These results are inconsistent with the disparity minimisation hypothesis. In order to account for the discrepant findings of the two studies, we propose that vertically oriented nonius lines may not be a valid method for assessing cyclovergence because the lines can be seen as lying 'within' the inclined surface. In experiment 2, we tested the predictions of the cyclovergence hypothesis of Frisby et al against our own 'within surface' explanation, using both horizontally and vertically oriented nonius lines and dichoptic images related by either a horizontal or a vertical shear. If cyclovergence were the cause of the misalignment, both horizontal and vertical nonius lines should appear misaligned to the same extent. This was not found to be the case. We conclude that vertical nonius lines may not be a valid technique for measuring cyclovergence when the lines are seen against a background of an inclined surface.     

Differential hemispheric mediation of nonverbal visual stimuli.

Studies employing schematic faces of three features explored the role of the left hemisphere as an analytic processor in difficult discriminations and the role of the right hemisphere in easy gestalt matches. In a discrimination task, the successively presented members of a stimulus pair differed in all three features. When both stimuli went to the same visual field there was a Visual Field X Judgments interaction; judgments same were processed faster in the left visual field. When a test stimulus differing on all three features from a previously memorized target face was matched to the latter, both judgments same and different were made faster for stimuli in the left visual field. However, when the test stimulus and the memory items differed on only one feature the right field proved superior for both judgments same and different.     

Attention and hemispheric differences in reaction time during simultaneous audio-visual tasks

The effect of different types of competing auditory tasks on laterality differences in visual perception was investigated. Right-handed subjects were presented with digits which occurred randomly in the left or right visual fields. They responded vocally to previously specified digits in a go, no-go reaction time situation. In the absence of any competing auditory task, digits presented in the right visual field were processed more quickly. This visual field difference in reaction time was in the same direction while subjects performed a secondary musical task. However, when a secondary verbal task had to be performed, digits in the left visual field received faster responses. The results support the view that the right hemisphere is capable of some language functions, and that hemispheric differences in performance have at their basis a quantitative asymmetry, which can be reversed even in normal subjects by overloading their limited capacity.     

Effect of different delayed auditory feedback intervals on a music performance task

The effects of 12 different delay intervals were studied in a musical task involving performance on an electronic organ. Disruption was found to occur to a degree comparable to similar studies involving verbal and rhythmic tasks under DAF. Maximal disruption was found with a delay of 0.27 sec, a value rather greater than that typically found to be most disruptive in speech. Three of the 12 Ss showed speeded performance under part of the range of DAF intervals, as compared with performance under immediate feedback; however, their performance also reached a peak of slowing at a delay of about 0.27 sec. No significant differences were found between male and female Ss’ performance. These findings were discussed without the context of control processes operating in music performance, and compared with the possibly analogous mechanisms of speech.     

The perception and identification of mirror-reversed patterns

Many species have difficulty in discriminating between mirror-image stimuli, especially those about a vertical axis, and when identificatory rather than purely perceptual processes are involved. Various theories are reviewed. In two experiments involving same-different judgments for pairs of stimuli, triangles or semicircles, these were simultaneously presented either unilaterally or bilaterally, and in mirror or aligned orientations with respect to each other. Mirror oriented stimuli presented to opposite cerebral hemispheres were no more readily matched than those possessing the same orientations (aligned), thus suggesting that at the perceptual level there is no interaction between mirror-corresponding points in the two visual cortices. Foreknowledge of stimulus orientations failed differentially to affect the findings. Two other studies were performed involving manual identification of single letters, correct or mirror oriented, in either visual field. Here, for most subjects, mirror reversal proved either less disruptive or even advantageous when in the visual field which is normally inferior with correctly oriented material. It was concluded that mirror-image confusion at the level of memory is almost certainly a consequence of reversed coding, in some form, in the opposite sides of the brain. A number of incidental findings were made with respect to visual field effects.     

Effect of punishment on human variable-interval performance

Three female human subjects pressed a button for monetary reinforcement in a range of variable-interval schedules specifying different frequencies of reinforcement. On alternate days, responding was also punished (by subtracting money) according to a variable-ratio 34 schedule. In the absence of punishment, rate of responding was an increasing negatively accelerated function of reinforcement frequency; the relationship between response rate and reinforcement frequency conformed to Herrnstein's equation. The effect of the punishment schedule was to suppress responding at all frequencies of reinforcement. This was reflected in a change in the values of both constants in Herrnstein's equation: the value of the theoretical maximum response-rate parameter was reduced, while the parameter describing the reinforcement frequency corresponding to the half-maximal response rate was increased.