Hemispheric asymmetries for complex visual patterns

Three tachistoscopic studies examined the laterality of spatial-form perception in normal adults using randomly generated eight-point and 12-point patterns (Vanderplas & Garvin, 1959) as the lateralized stimuli. In the first study of recognition accuracy, 36 subjects were tested in a partial replication of Fontenot. No laterality effects were found, and over-all recognition was better for the more complex 12-point patterns. In a second similar study with 20 subjects, the lateralized stimulus was followed by a central masking pattern. A left-hemisphere superiority for recognition and better over-all recognition for more complex patterns was obtained. These data do not support Fontenot's report of right-hemisphere superiority in complex visuospatial processing. Given these diverse findings, a reaction time study using mental rotation was conducted using the same patterns to determine whether latency would reflect accuracy of recognition. Twenty-six subjects judged whether a rotated lateralized test pattern was the same or different from a central target pattern. Measures of both latency and accuracy were separately assessed. No main effect of visual field was obtained on either measure. These studies suggest that the nature of hemispheric involvement in spatial form perception is far from resolved.     

Binocular interaction of orientation and spatial frequency channels: Evoked potentials and observer sensitivity

The interaction between size and orientation feature processing in the human visual system was investigated. Both observer sensitivity (d’ss) and the visual evoked potential (VEP) to test gratings flashed to one eye were investigated as a function of the nature of a continuously presented suppressing grating viewed either by that same eye or the opposite eye. The test and suppressing gratings were varied both in bar width (9′ss vs. 36′ss) and orientation (vertical vs. horizontal). The continuous grating intra- and interocularly suppressed the monocular VEPs to the flashed grating, the specificity of the suppression depending on the latency at which VEP amplitude was measured. VEP amplitude measured at early latencies (100–125 msec) was suppressed primarily when the flashed and continuous gratings were the same orientation, regardless of size. Starting at about 200 msec, and thereafter, VEP amplitudes were suppressed when the continuous bars were either the same orientationor size as the flashed bars. Late latencies, starting at 220 msec, and thereafter, were suppressed primarily when the bars in the two gratings were the same orientation and size. The reduction in observer sensitivity (d′ss) paralleled the changes found in the late VEP measures. These effects were evident under both the intraocular and interocular suppressing conditions. This pattern of VEP suppression, measured across eight points in the VEP waveform, was interpreted as indicating the existence of a sequence of channels that are specific first to a particular grating orientation, then to either a particular grating spatial frequency or orientation, and finally to the conjunction of a particular orientation and spatial frequency. Both sequential and parallel feature processing appears to take place in the human visual cortex, with grating orientation being encoded earlier than grating size.     

The relationship between visual persistence and event perception in bistable motion display

Observers viewed two alternating frames, each consisting of three rectangular bars displaced laterally by one cycle in one frame with respect to the other. At long interframe intervals (IFIs) observers perceived a group of three bars moving as a whole (group motion), and at short IFIs the overlapping elements in the two frames appeared stationary, while the third element appeared to move from one end of the display to the other (element motion). The upper temporal limit for perceiving element motion was reduced when bars with blurred edges were used and when either frame duration or bar size was increased. However, when inner and outer elements had different sizes, the element motion percept was dominant up to 230 ms IFI. These findings may be interpreted in terms of spatial tuning of motion mechanisms involved in the perception of bistable apparent motion.     

Age-Related Differences in Implicit Learning of Non-Spatial Sequential Patterns

This experiment investigated whether there are age differences in implicit learning of non-spatially arranged sequential patterns. We tested 12 young and 12 old participants for five sessions each in a non-spatial alternating serial reaction time (ASRT) task, in which predictable pattern events alternated with random, unpredictable ones. People of both ages were able to learn the sequence, but older people showed less pattern sensitivity than younger ones. Neither group was able to exhibit declarative knowledge of the pattern or to discriminate between pattern and random sequences on a recognition test, suggesting that the learning was indeed implicit. These findings indicate that the age deficits previously observed in the learning of spatial sequences are not due solely to age-related deficits in visuo-spatial attention or control of eye movements, but rather reflect a more general deficit in the ability to learn subtle sequential regularities.     

Spatial Conceptual Influences on the Coordination of Bimanual Actions: When a Dual Task Becomes a Single Task

When the left and right hands produce 2 different rhythms simultaneously, coordination of the hands is difficult unless the rhythms can be integrated into a unified temporal pattern. In the present study, the authors investigated whether a similar account can be applied to the spatial domain. Participants (N = 8) produced a movement trajectory of semicircular form in single-limb and bimanual conditions. In the bimanual tasks, 1 limb moved above the other in the frontal plane. Bimanual unified tasks were constructed so that the spatial paths to be produced by the 2 limbs could be easily conceptualized as parts of a unified circle pattern. Bimanual distinct tasks availed a less obvious spatial pattern that would unify the 2 tasks. Performance of the spatial patterns was more accurate in the unified task, despite similar demands placed on the coordination dynamics between the limbs in the 2 cases (e.g., the phase relations). The authors conclude that a dual task becomes a single task, and interlimb interference is reduced, when the spatial patterns produced by the 2 hands form a geometric arrangement that can be conceptualized as a unified representation.     

Visually controlled matching of pattern movement.

Subjects were asked to match the speeds of two moving random-dot patterns seen through circular apertures. The speed of one pattern that moved horizontally toward the right of a computer screen changed continuously. The speed of this pattern represented the target. It was to be matched with the speed of the second pattern, which moved in the opposite direction. The subject controlled the speed of the second pattern by means of an isometric joystick. The distance between the apertures on the screen as well as the subject's distance from the screen served as experimental parameters. In this way, the effects of both spatial and temporal transients of pattern speed on human tracking performance were studied. To avoid anticipation by the subject, the amplitude and the frequency of the target pattern speed changed pseudorandomly. The accuracy with which the subject performed the matching task was influenced by the mean pattern speed and the parameters of the visual field. Within lower velocity ranges, the subject's sensitivity to the instantaneous speed differences varied according to Weber's law. The cross-correlation of the velocity time courses decreased when the mean speed of the target pattern was increased. Two stimulus parameters had a strong influence on the modulation of the correlation value: (1) the angular size of the stimulus on the retina and (2) the retinal eccentricity of the stimulus.     

Evidence against independent processing of black and white pattern features

Following adaptation to a rectangular grating, subjects observed a shift in the perceived duty cycle of a test grating (Burton, Nagshineh, & Ruddock, 1977; DeValois, 1977). This suggests that size information about black and white pattern components may be analyzed independently. We have tested this hypothesis by combining adaptation to a 2-cpd rectangular wave grating (narrow white bars and wide black bars or vice versa) with adaptation to a 4-cpd sine wave (narrow white and black bars. The data do not support the independent analysis of white and black components, but they may be accounted for by mechanisms sensitive to the relative phase relations among the spatial frequency components of the input.     

Temporal characteristics of the effects of visual pattern redundancy on encoding and storage processes: evidence from rapid serial visual presentation

Pattern redundancy is a key concept for representing the amount of internal mental load (encoding efficiency) needed for pattern perception/recognition. The present study investigated how pattern redundancy influences encoding and memory processes in the visual system using a rapid serial visual presentation (RSVP) paradigm. With RSVP, it is well known that participants often fail to detect repetitions of words (repetition blindness, RB). We used this phenomenon as an index of the encoding and storage of visual patterns. In three experiments, we presented patterns with higher and lower redundancy, as defined by Garner’s equivalent set size (ESS). The results showed that RB occurred more frequently for higher redundancy patterns when the temporal distance between the targets was less than 500 ms; this tendency was reversed with longer temporal distances of over 500 ms. Our results suggest that pattern redundancy modulates both the early encoding and subsequent memory processes of a representation.     

A biologically based model for recognition of 2-D occluded patterns

In this work, we present a biologically inspired model for recognition of occluded patterns. The general architecture of the model is based on the two visual information processing pathways of the human visual system, i.e. the ventral and the dorsal pathways. The proposed hierarchically structured model consists of three parallel processing channels. The main channel learns invariant representations of the input patterns and is responsible for pattern recognition task. But, it is limited to process one pattern at a time. The direct channel represents the biologically based direct connection from the lower to the higher processing level in the human visual cortex. It computes rapid top-down pattern-specific cues to modulate processing in the other two channels. The spatial channel mimics the dorsal pathway of the visual cortex. It generates a combined saliency map of the input patterns and, later, segments the part of the map representing the occluded pattern. This segmentation process is based on our hypothesis that the dorsal pathway, in addition to encoding spatial properties, encodes the shape representations of the patterns as well. The lateral interaction between the main and the spatial channels at appropriate processing levels and top-down, pattern-specific modulation of the these two channels by the direct channel strengthen the locations and features representing the occluded pattern. Consequently, occluded patterns become focus of attention in the ventral channel and also the pattern selected for further processing along this channel for final recognition.     

The effects of intensity and interval rhythms on the perception of auditory and visual temporal patterns

Repeating temporal patterns were presented in the auditory and visual modalities so that: (a) all elements were of equal intensity and were equally spaced in time (uniform presentation); (b) the intensity of one element was increased (accent presentation); or (c) the interval between two elements was increased (pause presentation). Intensity and interval patterning serve to segment the element sequence into repeating patterns.

For uniform presentation, pattern organization was by pattern structure, with auditory identification being faster. For pause presentation, organization was by the pauses; both auditory and visual identification were twice as fast as for uniform presentation. For auditory accent presentation, organization was by pattern structure and identification was slower than for uniform presentation. In contrast, the organization of visual accent presentation was by accents and identification was faster than for uniform presentation. These results suggest that complex stimuli, in which elements are patterned along more than one sensory dimension, are perceptually unique and therefore their identification rests on the nature of each modality.     

The role of scanpaths in the recognition of random shapes

Eye movements of 12 Ss were examined during learning and recognition of two-dimensional random shapes to determine the nature of the memorial representation of a stimulus and the utilization of this memorial representation in pattern recognition. Specifically, the purpose of this study was to test the scanpath model of pattern perception by determining whether scanpaths exist and, if so, how they influence recognition performance. Scanpaths, defined as overlapping fixation patterns in learning and recognition tasks, were observed in over half of all eye-movement records regardless of shape complexity. Presence of scanpaths did not increase recognition performance as measured by errors in recognition and Ss’ ability to reproduce the shapes. Although scanpaths did not influence recognition performance, their occurrence implicates them as a potential factor in the recognition process.     

Counterexample to the hypothesis of functional similarity between tactile and visual pattern perception

In earlier work, the author has demonstrated that tactile pattern perception and visual pattern perception exhibit many parallels when the effective spatial resolution of vision is reduced to that of touch, thus supporting the hypothesis that the two pattern senses are functionally similar when matched in spatial bandwidth. The present experiments demonstrate a clear counter-example to this hypothesis of functional similarity. Specifically, it was found that the lateral masking effect of a surround on tactile character recognition increases when the surround changes in composition from solid lines to dots, whereas for vision, recognition performance goes in the opposite direction. This finding necessitates some modification of the model of character recognition proposed by the author (Loornis, 1990) as it applies to the sensing of raised tactile patterns. One possible modification would be to incorporate, as the initial stage of pattern transformation, the continuum mechanics model for the skin that was developed by Phillips and Johnson (1981b).     

Sex differences in memory for landmark arrays in C57BL/J6 mice

The most robust sex differences in cognition across polygynous mammalian species are the sex-specific patterns of the use of spatial cues during encoding and orientation. In laboratory rats, wild rodents, and humans, females orient preferentially to the features and arrangement of local landmarks, while males preferentially attend to distant landmarks. Yet this sex-specific pattern is often absent or reversed in the laboratory mouse, a species representing a major laboratory model of neural mechanisms. We explored sex differences in the C57BL/J6 strain of laboratory mouse by employing tasks that were motivated by the natural patterns of exploration. We predicted that such tasks would unmask the predicted default polygynous patterns of cue use by females and males. We used two standard tasks, a novel object recognition task and a five-stage serial object dishabituation task. On the first task, the results showed a female advantage in detecting the novel object, as predicted by prior results from other polygynous species. In the second task, we found, also as predicted, a male advantage in performance when the polarization of the array was distorted and a female advantage in performance when the local array was re-arranged. The pattern of sex-specific advantages in performance in C57BL/J6 mouse is thus concordant with that found in other polygynous mammals.     

Stimulus complexity, EEG abundance gradients, and detection efficiency in a visual recognition task.

Occipital EEG was monitored while subjects inspected 27 projected patterns. The number (N) and variety (V) of elements in the patterns were varied systematically. There were three levels of N (6, 12 or 24 elements) and three levels of V (circles, squares or hexagons occupying all, one half or one third of the element locations for all levels of N). Subjects were instructed that they would be required in a post-test to recognize the patterns, among patterns which had not appeared; they were also informed that the patterns had been constructed according to a set of simple rules, but the nature of these rules was not made fully explicit. The EEG was quantified by means of low-frequency analysis, yielding measures of abundance (theta, alpha and beta) and mean dominant frequency. For the recognition task, nine stimulus items were embedded among 45 items. Recognition efficiency was measured by means of the signal detection theory discrimination index (d'). The results were as follows: (i) Both N and V were inversely related to alpha abundance (P less than 0-01); (ii) the strongest relationship between stimulus parameters and the EEG held for N and EEG beta activity (13-5-19-5 Hz;P less than 0-001), where again the EEG and N were inversely related; (iii) there was a significant (P less than 0-05) direct relationship between N and theta activity; (iv) contrary to prediction, mean dominant alpha frequency decreased as N increased; (v) d' correlated significantly with a number of effects for N, i.e. subjects who exhibited greatest EEG discriminability of items during exposure of the patterns, subsequently obtained the higher detection scores in the recognition task. The work described therefore demonstrates that only only do stimulus parameters have systematic effects upon brain activity as measured by the EEG, but that such effects have functional value and reflect aspects of efficiency. The results are fully compatible with arousal theory constructs relating physiological reactivity and performance.     

The influence of augmented feedback and prior learning on the acquisition of a new bimanual coordination pattern

The present research examined two variables regarding the acquisition of a new bimanual coordination pattern: the role of previous experience and the nature of augmented feedback. Two groups of participants acquired a new coordination pattern (135 degrees relative phase) following two sessions of practice of another novel pattern (90 degrees relative phase). Transfer of learning in these groups was compared to two groups that had not previously learned a new pattern, but were nevertheless influenced by coordination patterns that are intrinsic to the task of bimanual relative timing (in-phase, 0 degrees, and anti-phase, 180 degrees). The findings revealed that new learning overshadowed the influence of the intrinsic patterns. Learning was also greatly affected by augmented feedback: dynamic, on-line pursuit tracking information was more effective in transfer than static, terminal feedback. Implications of these findings regarding theoretical constructs in motor learning are discussed.     

Discrimination of structure: II. Feature binding

In 3 experiments, pigeons acquired a discrimination between patterns comprising the same features. Thus vertical green bars beside horizontal red bars might have signaled food, and horizontal green bars beside vertical red bars might have signaled no food. The solution of this discrimination can be explained by assuming each pattern is represented either by a template or by structural features that are sensitive to combinations of color and line orientation. The 1st explanation predicts subjects should react to a training pattern rotated 90 degrees in the same way as the pattern on which it is based. The 2nd explanation predicts these patterns should be treated as if they signal opposing outcomes. The experiments confirmed the 2nd of these predictions.     

Mapping Good Therapy Sessions: A Pilot Study of Within-Session Client Affect

The purpose of the present study was to measure client affect over small timescales within therapy sessions, in order to identify affective patterns that might distinguish good versus poor sessions. Toward this end, patterns of affect were observed across 15-s intervals throughout one therapy session for each of four different clients being treated for generalized anxiety disorder using cognitive-behavioral therapy. The primary hypothesis was that during “good” therapy sessions (as defined by high session alliance scores and good therapy outcomes), clients would exhibit a pattern of positive–negative–positive (PNP) affect during the course of the session, reflecting prolonged periods of negative affect consistent with productive therapeutic work, situated between periods of positive feeling. Clients in “poor” sessions were not expected to show this pattern. The findings were consistent with predictions. There was also a non-significant trend suggesting that clients in good sessions demonstrated a greater frequency of very small PNPs—as brief as 45 s—suggesting a potentially greater number of “micro-episodes” of therapeutic work. Implications of the findings are discussed.     

Parallel coding of conjunctions in visual search

Two experiments investigated whether the conjunctive nature of nontarget items influenced search for a conjunction target. Each experiment consisted of two conditions. In both conditions, the target item was a red bar tilted to the right, among white tilted bars and vertical red bars. As well as color and orientation, display items also differed in terms of size. Size was irrelevant to search in that the size of the target varied randomly from trial to trial. In one condition, the size of items correlated with the other attributes of display items (e.g., all red items were big and all white items were small). In the other condition, the size of items varied randomly (i.e., some red items were small and some were big, and some white items were big and some were small). Search was more efficient in the size-correlated condition, consistent with the parallel coding of conjunctions in visual search     

Investigating the anticipatory nature of pattern perception in sport

The aim of the present study was to examine the anticipatory nature of pattern perception in sport by using static and moving basketball patterns across three different display types. Participants of differing skill levels were included in order to determine whether the effects would be moderated by the knowledge and experience of the observer in the same manner reported previously for simple images. The results from a pattern recognition task showed that both expert and recreational participants were more likely to anticipate the next likely state of a pattern when it was presented as a moving video, but only the experts appeared to have the depth of understanding required to elicit the same anticipatory encoding for patterns presented as schematic images. The results extend those reported in previous research and provide further evidence of an anticipatory encoding in pattern perception for images containing complex, interrelated patterns.     

Context effects in visual pattern recognition by pigeons

In the experiments described in this paper we examined the effects of contextual stimuli on pigeons’ recognition of visual patterns. Experiment z showed acontext-superiority effect. Specifically, two target forms that were identical except for location in the visual field were not discriminated when presented alone, but the compounds formed when each of these targets was placed between a nearby pair of flanking stimuli were readily discriminated. The size of the context-superiority effect decreased with increasing target-flanker separation. In Experiments 2 and 3 the two targets differed in form rather than spatial location and were readily discriminated in the absence of Hankers. Under these circumstances, adding an identical pair of flankers to each target resulted in a content-inferiority effect; that is, the two target-plus-Hankers compounds were less readily discriminated than the targets atone. The size of the context-inferiority effect decreased with increasing target-flanker separation. The observed effects of context are predictable from the Heinemann-Chase (1990) model of pattern recognition.