Recall of digits projected to temporal and nasal hemi-retinas

Fourteen right-handed, right eye dominant subjects recalled digits when different ones were projected simultaneously to either temporal or nasal retinas. The principal findings were: (a) Recall of digits projected to nasal retinas was significantly better than when projected to temporal retinas; (b) information projected to the right eye was recalled significantly better than that projected to the left eye. It is shown that the relative ineffectiveness of the recall of input from the non-dominant eye can be attributed almost wholly to the relative inefficient recall of digits projected to the left temporal retina.     

Handedness, eye-dominance, and immediate memory

Twenty male university students varying in handedness and eye-dominance recalled conventional and unconventional digits under two conditions: (1) when the same type of digit was projected simultaneously to each eye, and (2) when a different type of digit was projected simultaneously to each eye.

Forty trials were given, each consisting of four pairs of digits with a different numeral projected to each eye. Performance was analysed in terms of percentage recalled correctly and time of onset of each response.

Right eye-dominant groups, particularly a right handed and right eye-dominant group, were superior in both accuracy of recall and speed of response to left eye-dominant groups. Least able in recall were left handed, left eye-dominant subjects. Superiority of right eye-dominant groups was especially marked when a different type of digit was projected to each eye.

In accord with results reported by Broadbent for the ears (1956, 1957), other results suggest it is possible for the eyes to operate simultaneously as independent information sources. However, unlike the case for audition, present subjects did not report all information from one eye before that from the other, but gave it in pairs. It seems that the capacity of the eyes to function independently depended upon eye-dominance and handedness, while serial ordering of responses reflected imposition of an habitual response organization.     

Enhanced recency effects with changing-state and primary-linguistic stimuli

A number of explanations for the modality effect in immediate serial recall have been proposed. The auditory advantage for recall of recency items has been explained in terms of (1) the contributions of precategorical acoustic storage (PAS), (2) an advantage of changing-state over static stimuli, and (3) an advantage of primary-linguistic coding. Four experiments were conducted to evaluate these hypotheses. In the first, subjects viewed seven consecutive rectangles of different colors on a computer monitor. A small recency effect was obtained when the task was to recall the colors of the rectangles in order, with the size of the effect being independent of whether the rectangles remained stationary on the screen or moved in one of four directions. However, when the task was to recall the direction of movement of the rectangles, a larger recency effect was found. This pattern of results was interpreted as suggesting that recency effects are enhanced by changing-state stimulus information, but only when the changing-state information serves to identify the stimulus. Experiments 2 and 3 provided converging evidence by demonstrating an analogous recency advantage for changing-state visual stimuli that were somewhat different from those of Experiment 1. Experiment 4 demonstrated recency effects with synthesized speech stimuli that were substantially greater than were those found with the changing-state visual stimuli of the first three experiments. Implications of the results for the PAS, changing-state, and primary-linguistic hypotheses, as well as temporal-distinctiveness theories of recency, are discussed.     

The influence of dimensionality on eye fixations.

Eye fixation patterns were explored for sixty adult subjects, each of whom viewed one of three stimuli, either in a three-dimensional model format or in a two-dimensional photographic format. The stimuli consisted of one symmetrical and two asymmetrical color representational drawings displayed in the form of a photograph or of a model. Total fixation times (in ms) were computed for seven portions of each stimulus: top, bottom, left, right, foreground, middle ground, and background. Results indicated that for all stimuli, subjects viewing the 3-D model spent significantly more time fixating the foreground and significantly less time fixating the background than subjects viewing the 2-D photograph. For the two asymmetrical stimuli subjects in the two groups differed significantly in their fixation patterns for the left/right variables. It was concluded that eye fixation patterns vary as a function of dimensionality.     

After effect of seen movement: Evidence for peripheral and central components

Three experiments showed that the movement after-effect (MAE) contains both peripheral and central components. In Experiment I, the left eye viewed a sectored disc rotating to the left, and the right eye viewed a disc rotating to the right, on corresponding retinal areas. Result: when each eye in turn then viewed a stationary disc, the left eye saw a MAE to the right, and the right eye a MAE to the left. These MAE_s must be peripheral.

In Experiment II, it was arranged that the movement information was shared out between the eyes, using a ring of lights which were switched on and off to give rotating phi movement. It was arranged that each eye on its own saw a random flashing oscillation but the two eyes together saw rotation anticlockwise. Result: a clockwise MAE was seen, which must be central.

In Experiment III, the switching programme was modified to arrange that now each eye on its own saw rotation clockwise, but the two eyes together saw rotation anticlockwise. Result: a clockwise MAE was seen, which must be central. (Peripheral MAE_s from each eye on its own would have been anticlockwise.)     

Visually perceived eye level with reversible pitch stimuli: implications for the great circle and implicit surface models

Visually perceived eye level (VPEL) and perceived pitch were measured while subjects viewed two sets of stimuli that were either upright or pitched top-toward or top-away from them. The first set of stimuli, a pair of vertical lines viewed at various angles of pitch, caused systematic changes in perceived pitch and upward and downward VPEL shifts for the top-toward and top-away pitches, respectively. Neither the perceived pitch nor the VPEL measures with these stimuli differed between monocular and binocular viewing. The second set of stimuli was constructed so that, when viewed at the appropriate pitch angle, the projected orientations of the lines in the retinal image of each stimulus were similar to those generated by a pair of vertical lines pitched by a lesser amount in the opposite direction. When viewed monocularly, these stimuli appeared pitched in the direction opposite their physical pitch, yet produced VPEL shifts consistent with the direction of their physical pitch. These results clearly demonstrate a dissociation between perceived pitch and VPEL. The same stimuli, when viewed binocularly, appeared pitched in the direction of their physical pitch and caused VPEL shifts indistinguishable from those obtained monocularly. The retinal image orientations of these stimuli, however, corresponded to those of vertical line stimuli pitched in the opposite direction. This finding is therefore consistent with the hypothesis that VPEL and perceived pitch are processed independently, but inconsistent with the specific version of this hypothesis which states that differences in VPEL are determined solely on the basis of the orientation of lines in the retinal image.     

Recall of familiar objects and projected color photographys of objects by mentally retarded individuals of comparable mental age.

The effects of cue-availability on short-term and long-term recall of 40 mentally retarded children were investigated. Subjects were chosen on the basis of comparable mental age (approximately 90 mo.) and randomly assigned to either an objects (high cues) group or slides (low cues) group. 52 familiar objects served as stimuli for the objects group and projected color photographs of the objects were presented to the slides group. In the short-term recall session the subjects were shown stimuli grouped into eight trials and asked to recall the names of the stimuli in each trial ten seconds after presentation. Delayed recall was obtained 48 hr. later in a free recall session. The objects group scored significantly higher than the slides group on memory span (p less than .01), short-term recall (p less than .001), and delayed recall (p less than .025). The facilitation of recall achieved by using three-dimensional stimuli was clearly demonstrated, and the relative degree of facilitation was comparable for both short- and long-term recall.     

Eye scanpaths during visual imagery reenact those of perception of the same visual scene

Eye movements during mental imagery are not epiphenomenal but assist the process of image generation. Commands to the eyes for each fixation are stored along with the visual representation and are used as spatial index in a motor‐based coordinate system for the proper arrangement of parts of an image. In two experiments, subjects viewed an irregular checkerboard or color pictures of fish and were subsequently asked to form mental images of these stimuli while keeping their eyes open. During the perceptual phase, a group of subjects was requested to maintain fixation onto the screen's center, whereas another group was free to inspect the stimuli. During the imagery phase, all of these subjects were free to move their eyes. A third group of subjects (in Experiment 2) was free to explore the pattern but was requested to maintain central fixation during imagery. For subjects free to explore the pattern, the percentage of time spent fixating a specific location during perception was highly correlated with the time spent on the same (empty) locations during imagery. The order of scanning of these locations during imagery was correlated to the original order during perception. The strength of relatedness of these scanpaths and the vividness of each image predicted performance accuracy. Subjects who fixed their gaze centrally during perception did the same spontaneously during imagery. Subjects free to explore during perception, but maintaining central fixation during imagery, showed decreased ability to recall the pattern. We conclude that the eye scanpaths during visual imagery reenact those of perception of the same visual scene and that they play a functional role.     

Eye movements under different rehearsal strategies.

Eye movements were recorded while subjects studied lists of simultaneously presented words. The 24 subjects in the storage group studied for immediate recall, and the 24 subjects in the coding group studied primarily for a later, final recall. Those subjects in the coding group had longer eye fixations and fewer regressions than did subjects in the storage group. In addition, the subjects in the coding group recalled fewer words in immediate recall and more words in final recall than did the subjects in the storage group. These results were interpreted as supporting the elaboration hypothesis of coding in rehearsal, which states that coding into long-term store consists of rehearsing both old and new information in short-term store. The results did not support the concentration hypothesis, which states that coding into long-term store consists of intensively rehearsing a smaller number of items than rehearsed under a storage strategy. The eye movement data also indicate that subjects read about twice as many words as they overtly rehearse.     

Disappearance of afterimages at 'impossible' locations in space

An eccentrically positioned afterimage, viewed in the dark, will disappear if the eye is positioned so that the afterimage now projects to a more extreme location relative to straight ahead. It was found that the afterimage disappeared when it projected to a location which corresponded to the edge of the visual field defined by the brow, cheek, and nose. This suggests that visibility of stimuli from those retinal regions shadowed by the head is influenced by eye-position information.     

Interference with Rehearsal in Spatial Working Memory in the Absence of Eye Movements

We have previously argued that rehearsal in spatial working memory is interfered with by spatial attention shifts rather than simply by movements to locations in space (Smyth & Scholey, 1994). It is possible, however, that the stimuli intended to induce attention shifts in our experiments also induced eye movements and interfered either with an overt eye movement rehearsal strategy or with a covert one. In the first experiment reported here, subjects fixated while they maintained a sequence of spatial items in memory before recalling them in order. Fixation did not affect recall, but auditory spatial stimuli presented during the interval did decrease performance, and it was further decreased if the stimuli were categorized as coming from the right or the left. A second experiment investigated the effects of auditory spatial stimuli to which no response was ever required and found that these did not interfere with performance, indicating that it is the spatial salience of targets that leads to interference. This interference from spatial input in the absence of any overt movement of the eyes or limbs is interpreted in terms of shifts of spatial attention or spatial monitoring, which Morris (1989) has suggested affects spatial encoding and which our findings suggest also affects reactivation in rehearsal.     

Effect of structured visual environments on apparent eye level

Each of 12 subjects set a binocularly viewed target to apparent eye level; the target was projected on the rear wall of an open box, the floor of which was horizontal or pitched up and down at angles of 7.5 degrees and 15 degrees. Settings of the target were systematically biased by 60% of the pitch angle when the interior of the box was illuminated, but by only 5% when the interior of the box was darkened. Within-subjects variability of the settings was less under illuminated viewing conditions than in the dark, but was independent of box pitch angle. In a second experiment, 11 subjects were tested with an illuminated pitched box, yielding biases of 53% and 49% for binocular and monocular viewing conditions, respectively. The results are discussed in terms of individual and interactive effects of optical, gravitational, and extraretinal eye-position information in determining judgements of eye level.     

Imagery vividness, hypnotic susceptibility, and the perception of fragmented stimuli

Two experiments were conducted to determine the role of hypnotic susceptibility level (high or low) and imaging ability (vivid or poor) in the performance of gestalt closure tasks. In Experiment 1, subjects were required to identify fragmented stimuli in the Closure Speed Test and in the Street Test. In Experiment 2, subjects reported on fragmented stimuli that were projected to the right eye and subsequently produced an afterimage. Individuals were asked to identify the composite if possible and to report on the duration of the afterimage. In both experiments, hypnotic susceptibility level and imaging ability affected reports of gestalt closure. The greatest number of correct closures was reported by those who were both high in hypnotic susceptibility and vivid in imaging ability. In addition, in the second experiment, this group also reported the longest enduring afterimage. These results are discussed in terms of the processes required to perform in a gestalt closure task.     

Encoding specificity in the recall of pictures and words in children and adults

In this study, the modality of the retrieval cues (pictures or words) was varied in a cued recall task to determine how second and fourth grade children and college adults encode words (Experiment 1) and pictures (Experiment 2). According to the assumptions of the encoding specificity principle, cue modality should affect recall only to the degree to which subjects focus on modality specific (sensory) rather than nonmodality specific (semantic) information in stimuli. In both experiments, the results showed progressively smaller encoding specificity effects with increasing age. To ensure that differences in encoding activity were responsible for these effects, comparisons were made of recall patterns under intentional learn conditions, and under incidental conceptual and sensory orienting conditions. The recall patterns of the children in the conceptual orienting condition were similar to the adult patterns in the learn condition, and the adult recall patterns in the sensory orienting conditions were similar to those of the children in the learn conditions. These results suggest that there are developmental differences in encoding the sensory and semantic information in stimuli that may result from differences in the efficiency with which the semantic information in stimuli is processed. The results suggest that young children typically encode stimuli in a fashion that stresses the sensory aspects of the stimuli, and that recall suffers as a result.     

The cyclopean eye vs. the sighting-dominant eye as the center of visual direction

In three experiments, competing hypotheses concerning the center of visual direction were examined with the stimuli used in the Card test which requires a subject to position the card with a hole so that a target can be seen. Each experiment used six right- and six left-sighting-eye subjects. In Experiment 1, the aperture and the target were collinear with the sighting eye. The mean apparent locations of the aperture when the target was fixated, and of the target when the aperture was fixated, were consistent with only the cyclopean-eye hypothesis; that is, the 95% confidence intervals of these means contained the predicted values from the cyclopean-eye hypothesis but not those from the sighting-eye hypothesis. In Experiment 2, subjects moved the card from the side of the nonsighting eye, and in 88% of the trials it was stopped when the nonsighting eye viewed the target. In Experiment 3, the target was viewed through the aperture with both the sighting and nonsighting eye in six different stimulus arrangements. The 95% confidence intervals of all 12 mean apparent locations of the targets contained the predicted values from the cyclopean-eye hypothesis but none of those from the sighting-eye hypothesis. These results are compatible with the cyclopean-eye hypothesis, and we therefore conclude that the sighting eye is not the center of visual direction.     

Focal and nonfocal processing of color and form

Langley Porter Neuropychtatrte Institute, University of California, San Francisco. Californta 94122 Response latencies to color are usually shorter than those to form. but sometimes this difference is absent or reversed. Three experiments investigated whether these differences result from differential susceptibility of color and form to extra focal processing. Experiment I showed shorter same-difference latencies to color than to form when two stimuli were presented simultaneously. This difference disappeared or reversed when the two stimuh appeared sequentially. Experiment II. using a multistimulus matching task, found that differences between response latencies to form and color were minimal at the center of the display and increased peripherally. Experiment III showed that eye movements were more frequent in matching forms than colors. Tasks that produced many eye movements had long average latencies, but the relationship between eye movements and latency was not a simple one. There was evidence both for parallel and serial strategies tn the use of the eyes to gather information. The results of these experiments are considered in relation to a theory of distributed attention.     

Hemispheric specialization for processing of visually presented verbal and spatial stimuli

Two “same-different” reaction time experiments, analogous in task demands made on the S, were designed to test laterality differences in. perception. Ten normal right-handed Ss performed a verbal task in which they decided whether or not two three-letter words belonged to the same conceptual class. Ten different Ss performed a spatial task in which they decided whether two 16-cell matrices with 3 blackened cells were identical. Reaction times were found to be sensitive to laterality differences in perception. Verbal stimuli were processed faster when presented in the right visual field, and thus projected directly to the left cerebral hemisphere; spatial stimuli were processed faster when presented in the left visual field, and thus projected directly to the right cerebral hemisphere. These results were analyzed in terms of implications regarding hemispheric asymmetries for processing of verbal and spatial material and the nature of interhemispheric transfer of information.     

Heart-Rate responses (HRR) to lateralized visual stimuli

Direction of changes in heart-rate responses (HRR) were investigated in three separate experiments as a measure of differential cognitive and emotional specialization of the cerebral hemispheres. Visual stimuli were presented via the visual half-field technique in all three experiments. Slides with different contents were flashed for 200 msec on each trial either to the left or right of a center LED fixation point. The LED went on 5 seconds prior to slide onset. HR changes were scored as second-by-second deviations during 10 seconds after LED onset from pre-LED base line. In the first experiment it was hypothesized that emotionally relevant stimuli initially projected to only the right hemisphere would result in more anticipatory acceleration than when the same stimulus was initially projected to the left hemisphere. A picture of a snake and of a geometric figure were repeatedly briefly flashed to the right of the LED for half of the subjects, and to the left for the other half. There were 25 trials with an intertriai interval of 25–40 seconds. Results showed significant effects of deceleration as a function of the slide stimulus in all groups on seconds 5, 6, or 7 after onset of the center LED. Furthermore, an anticipatory acceleration was observed during the first trial-block on seconds 3 and 4 in the right hemisphere groups only with no differences between the neutral and emotional stimuli. In Experiments 2 and 3, a letter-string of six letters and a complex symmetric pattern were used as stimuli. These stimuli were chosen because previous research has clearly implicated the hemispheres to be differentially specialized in their ability to process verbal and visuo-spatial stimuli. The set-up was identical to Experiment 1, with the exception that differences in response to the two types of stimuli were evaluated on a within-subjects basis. The results from Experiments 2 and 3 showed stimulus-related deceleration, peaking on seconds 5–7 in all groups and an anticipatory acceleration peaking on seconds 3 and 4 in the right hemisphere groups, with decelerations during the corresponding seconds in the left hemisphere groups. The results are discussed in relation to recent findings by Walker and Sandman (1982) about the possibility of hemispheric specialization in psychologic influences on heart rate changes in response to environmental demands.     

Psychological analyses of haptic and haptic-visual judgements of extent

Magnitude estimates of haptic extent resulted in positively accelerated psychophysical power function with an exponent of 1.18. However, in two further experiments right-handed male subjects made rating-scale judgements of the combined width of two stimulus blocks. Six widths were used and five replications of the 36 factorial combinations were presented to each subject. In Experiment II both stimuli were out of view and one was held between the thumb and index finger of each hand. In Experiment III one stimulus was held out of view between thumb and finger of the right hand and the second was shown to the subject. Mean ratings in both experiments were fit by a model which assumes that responses are a weighted average of the scale values of the two stimuli (Anderson, 1974a).