Locus and persistence of capacity limitations in visual information processing.

Although there is considerable evidence that stimuli such as digits and letters are extensively processed in parallel and without capacity limitations, recent data suggest that only the features of stimuli are processed in parallel. In an attempt to reconcile this discrepancy, the simultaneously/successive detection paradigm was used with stimuli from experiments indicating parallel processing and with stimuli from experiments indicating that only features can be processed in parallel. In Exp I, with 30 undergraduates, large differences between simultaneous and successive presentations were obtained with an R target among P and Q distractors and among P and B distractors, but not with digit targets among letter distractors. As predicted by the feature integration theory of attention, false-alarm rates in the simultaneous condition were much higher than in the successive condition with the R/PQ stimuli. In Exp II, with 10 Ss, the possibility that attention is required for any difficult discrimination was ruled out as an explanation of the discrepancy between the digit/letter results and the R/PQ and R/PB results. Exp III (40 Ss) replicated the R/PQ and R/PB results of Exp I and extended these findings to a new set of stimuli. Exp IV (6 Ss) found that large amounts of consistent practice did not generally eliminate capacity limitations. It is concluded that the notion of capacity-free letter perception has limited generality. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Eye movements during parallel–serial visual search.

Two experiments (one using O and Q-like stimuli and the other using colored–oriented bars) investigated the oculomotor behavior accompanying parallel–serial visual search. Eye movements were recorded as participants searched for a target in 5- or 17-item displays. Results indicated the presence of parallel–serial search dichotomies and 2:1 ratios of negative to positive slopes in the number of saccades initiated during both search tasks. This saccade number measure also correlated highly with search times, accounting for up to 67% of the reaction time (RT) variability. Weak correlations between fixation durations and RTs suggest that this oculomotor measure may be related more to stimulus factors than to search processes. A third experiment compared free-eye and fixed-eye searches and found a small RT advantage when eye movements were prevented. Together these findings suggest that parallel–serial search dichotomies are reflected in oculomotor behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some parameters affecting shuttle-box avoidance responding with rats receiving serially presented conditioned stimuli.

Gave 48 male Blue Spruce rats shuttle-box training with serial or nonserial CS procedures. The serial CS condition (S1/S1S2), which involved a single stimulus for the 1st 1/2 of a 16-sec CS-UCS interval and 2 stimuli for the latter 1/2, produced shorter avoidance latencies and more avoidance responses when compared with a serial condition (S1/S2), in which the latter 1/2 of the interval involved only 1 stimulus. Both serial conditions resulted in longer avoidance latencies when compared to nonserial conditions. Exp. II with 144 Ss demonstrated that the above latency differences could be eliminated with shorter CS-UCS intervals, and Exp. III with 72 Ss suggested that avoidance-latency differences obtained at longer CS-UCS intervals were independent of the CS duration ratio between serial components. These and other findings were predicted from a generalization-decrement hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phonological loop and intermittent activity: A whistle task as articulatory suppression.

Examined whether the effect of articulatory suppression is due to the activation of an irrelevant phonology or to intermittent articulatory movements. In Exp 1, 24 undergraduates were tested for serial recall of visually presented letter sequences that were either phonologically similar or dissimilar, and had to remember each of the letter sequences under a no-suppression control or a suppression condition. In the suppression condition, half of the Ss were engaged in an intermittent speech suppression and the other half were in an intermittent whistle suppression task. The phonological similarity effects appeared in the control condition, but not in the suppression condition, irrespective of the type of suppression. In Exp 2, the phonological similarity effect again disappeared in the intermittent whistling condition, but not in the condition in which the 15 undergraduates required to engage a continuous whistling task. The results suggest that the effect of articulatory suppression was due to intermittent articulatory activity rather than the activation of an irrelevant phonology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual sampling after lesions of the superior colliculus in rats.

In 2 experiments with 20 male black-hooded rats, Ss with bilateral lesions of the superior colliculus showed significantly poorer relearning of a horizontal/vertical stripe discrimination than control Ss. In Exp I, all Ss showed disruption of performance when a stimulus–response (S–R) separation was introduced by raising the stimuli above the site of responding. However, colliculectomized Ss were much more disturbed by the S–R separation than were control Ss. In Exp II, all Ss showed lower performance levels when conflicting patterns were introduced into the upper portion of the stimulus doors, but this time Ss with collicular lesions were less disturbed than controls. It is suggested (a) that when the stimulus and response sites are discontinuous, rats must make an appropriate orienting response to effectively sample the visual stimuli and (b) that lesions of the superior colliculus alter performance by interfering with this orienting behavior. The impairment in relearning is attributed to the absence of preoperative overtraining on the discrimination task. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Search for a conjunctively defined target can be selectively limited to a color-defined subset of elements.

In conjunction search, response latencies usually increase with the number of displayed elements, suggesting serial, self-terminating search through all elements. In line with the results of H. Egeth, R. Virzi, and H. Garbart (1984), the present study shows that Ss do not necessarily search all display elements, but can limit their search to a color-defined subset of elements. The results make clear that selective search for a color-defined subset does not depend on saliency of the subset (Exp 1), that selective search can be purely color-based and does not depend on luminance (Exp 2), and that Ss can flexibly change which subset they are searching (Exp 3). Exp 4 showed that subset-selective search also occurs without fast absent responses as found in Exps 1–3 and that for selective search no explicit instruction is required. Subset-selective search is a likely strategy in conjunction search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensory preconditioning in rats following early visual deprivation.

Conducted 3 experiments in which a total of 131 light- and dark-reared (LR and DR) male hooded rats were given sensory preconditioning (SPC). In each experiment, Ss were presented with 2 stimuli either paired or unpaired, followed by conditioning to 1 and extinction on the other. 2 auditory stimuli were used in Exp. I. SPC was found for both LR and DR Ss, with no significant difference due to rearing condition either in acquisition or in the SPC test. In Exp. II, light and tone were employed; SPC was demonstrated and was more effective for LR than DR Ss. In Exp. III, rectangle stimuli were employed. The effect of SPC was evidenced in LR Ss; however, performance of DR Ss was not significantly different from that of controls. Results are discussed in terms of the effect of early visual deprivation on information-processing mechanisms. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Monitoring eye movements under conditions of associative matching, response production, and stimulus and response production.

Monitored eye movements in each of 3 studies with 20, 19, and 18 undergraduates, respectively, while Ss were given 8 study trials on a 7-item paired-associate list. Ss were then subjected to a single test trial of associative matching (Exp. I), response production (Exp. III) or stimulus and response production (Exp. IV). A 4th study with 42 Ss, (Exp. II), without eye movement monitoring, involved 3 groups of Ss given either 2, 4, or 6 study trials followed by a single test trial of associative matching. Results, with the exception of Exp. I, were generally consistent with a 2-stage notion of verbal paired-associate learning. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Factors influencing ocular motility during the performance of cognitive tasks.

Examined the relationship between ocular motility and specific cognitive processes in 2 experiments, using 50 undergraduates. In Exp I, eye movements (EMs) were videotaped as Ss attempted to answer verbal, visuospatial, or musical questions. Visuospatial questions elicited a lower lateral EM rate (EMR) and fewer vertical EMs than did verbal or musical questions. Results support a model that attributes ocular quiescence to interference between visual imagery and visual perception. In Exp II, lateral EMs were recorded electrically as Ss attempted to answer low-, moderate-, and high-imagery questions that required either a constrained or an unconstrained memory search. Constrained questions elicited a lower EMR than did unconstrained questions even when the effect of imagery was eliminated. Stimulus materials for the experiments are appended. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serial pattern learning: Teaching an alphabet to rats.

Two experiments determined whether 22 female albino Sprague-Dawley rats could learn an alphabet, which is a set of discriminably different stimuli, possessing the properties of an ordinal scale. For construction of the Ss' alphabet, 4 quantities of food were located in 4 arms of a radial arm maze, 1 quantity/arm, and Ss chose among the quantities without replacement (Exp I) or with replacement (Exp II) of previously chosen arms. If Ss could discriminate among the locations of the arms and their associated quantities and if they chose among the arms in some order that was a direct function of food quantity, there would be evidence that the set of arms had indeed become an alphabet. Both experiments showed that Ss ordered responses to the arms, choosing arms associated with larger quantities before selecting those associated with smaller quantities. Consequently, rats can learn an alphabet based on food quantity. Transfer tests show that Ss ordered without resorting to associative chaining mechanisms involving stimulus or response feedback among neighboring responses. There was some evidence that Ss appreciated transitive relations among the quantities. Findings support serial pattern learning in rats and other animals, and emphasize the utility of theoretical models based on human serial pattern learning in conducting such research. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Left hemisphere dysfunction and left hemisphere overactivation in schizophrenia.

Reports 2 experiments relating schizophrenia to functional brain asymmetry. In Exp I, 24 schizophrenics (mean age, 30.8 yrs) were compared to 24 matched controls (mean age, 37.3 yrs) on 2 tachistoscopic tasks (Syllable Test and Dot Location Test) designed to measure verbal and spatial information processing in the 2 hemispheres. Unlike the controls, the schizophrenics showed a right hemisphere superiority both on the verbal and on the spatial tests, indicating left hemisphere dysfunction in the initial processing of verbal information. In Exp II, lateral eye movements, as an index of contralateral hemispheric activation, were measured in a group of 24 paranoid schizophrenics (mean age, 28.9 yrs), 24 nonparanoid schizophrenics (mean age, 32.7 yrs), and 24 matched controls (mean age, 31.2 yrs). The eye movements were elicited by presenting the Ss with verbal neutral, verbal emotional, spatial neutral, and spatial emotional questions. The schizophrenics had significantly more rightward eye movement, compared to controls, regardless of question type, indicating left hemisphere overactivation. Results suggest that schizophrenia is associated with a pattern consisting of both left hemisphere dysfunction and overactivation. (63 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Information-limited parallel processing in difficult heterogeneous covert visual search.

Difficult visual search is often attributed to time-limited serial attention operations, although neural computations in the early visual system are parallel. Using probabilistic search models (Dosher, Han, & Lu, 2004) and a full time-course analysis of the dynamics of covert visual search, we distinguish unlimited capacity parallel versus serial search mechanisms. Performance is measured for difficult and error-prone searches among heterogeneous background elements and for easy and accurate searches among homogeneous background elements. Contrary to the claims of time-limited serial attention, searches in heterogeneous backgrounds instead exhibited nearly identical search dynamics for display sizes up to 12 items. A review and new analyses indicate that most difficult as well as easy visual searches operate as an unlimited-capacity parallel analysis over the visual field within a single eye fixation, which suggests limitations in the availability of information, not temporal bottlenecks in analysis or comparison. Serial properties likely reflect overt attention expressed in eye movements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of search procedures in real-life spatial environments.

Children's abilities to search for missing objects in real-life environments were investigated in 2 studies with a total of 70 2 yr 7 mo–6 yr 2 mo old Ss. Exp I involved searches of 8 locations on a school playground; Exp II involved searches of 8 large cupboards. In each study, Ss performed a free search followed by a logical search. In free search, the S was instructed to search the 8 locations to find a missing item. In logical search a critical search area within the 8 locations was defined for the Ss on the basis of (a) where the item was last seen and (b) where it was first discovered missing. In free search, more older than younger Ss searched each location at least once and searched all locations sequentially. Detailed comparisons of search patterns under the free and logical conditions revealed that older Ss understood the critical search area. In contrast, younger Ss' searches under the logical condition depended on one salient association of a location with the missing item. The developmental trends indicated that several memory and logical processes determine search procedures. The development and integration of these processes are discussed. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fear and affiliation in domesticated male rats.

Male rats actively seek the opportunity to interact with other male rats. Three experiments with 208 Long-Evans males examined the hypothesis that the presence of conspecifics can reduce the behavioral signs of fear and that this capacity provides part of the attraction to conspecifics. In Exp I, the immobility response was measured following exposure to a stressful noise. Ss that were observed in groups exhibited shorter durations of immobility than those observed alone. The "group" effect was sufficiently powerful to nullify different housing conditions and different degrees of familiarity among the Ss. Exp II compared social and nonsocial stimuli and found that only the former effectively reduced the immobility response. In Exp III, stressed Ss were more likely to choose to interact with a conspecific in a T-maze than were nonstressed Ss. Again, rearing conditions made little difference; both individually and group housed Ss were highly attracted to a conspecific. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conceptual automaticity in recognition memory: Levels-of-processing effects on familiarity.

Examined the effect of level of processing (LP) on recognition memory using 2 response-signal delays (RSD; 500 and 1500 msec). In Exp 1, LP (semantic or nonsemantic) and RSD were manipulated between 24 college students. In Exp 2, orienting task (pleasantness rating or letter judgment) and RSD were manipulated among 32 Ss. In Exp 3, study orientation and test instructions (inclusion or exclusion) were within-S factors, and RSD was a between-S factor. 32 Ss were included in Exp 3. In Exp 1, a modality effect was found for fast responses. The LP was reliable at both points in time. In Exp 2, fast responses were associated with significantly more "false-alarms" to words encoded semantically than those encoded nonsemantically. In Exp 3, both recollection and familiarity estimates were elevated by prior conceptual processing. Estimates of recollection were affected by RSD. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of UCS preexposure on excitatory and inhibitory rabbit eyelid conditioning: An associative effect of conditioned contextual stimuli.

Preconditioning experience with the UCS retards subsequent excitatory conditioning. Three experiments demonstrated that the UCS retardation effect is attenuated by associative manipulations of contextual stimuli of the UCS preexposure environment. The UCS retardation effect was reduced by (a) altering contextual stimuli between preexposure and conditioning (Exp I, 49 New Zealand male rabbits; Exp II, 28 Ss); and (b) latently inhibiting contextual stimuli subsequent to UCS (Exp III, 36 Ss). Although UCS preexposure retarded excitatory conditioning, results of Exp IV (48 Ss) demonstrated that UCS preexposure facilitated inhibitory conditioning. Overall findings indicate that an association between contextual stimuli and preexposed UCS contributes to the effects of preconditioning UCS experience on subsequent learning. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Processing nominal information during visual search.

Conducted 3 experiments to examine the processing of nominal information during a visual search. In Exp I, 6 experienced and 2 naive Ss searched for a single pre-specified target letter, and the stimulus exposure-time needed to yield a 50% (corrected for chance) level of accuracy was estimated using the parameter estimation by sequential testing procedure. Results show that the exposure-time was not influenced by the presence (in the irrelevant items) of the target's other case; this suggested that there was no obligatory accessing of nominal information during preattentive processing. In Exp II, 6 experienced Ss searched in Condition 1 for a single target which was specified as being one of a same-name pair of letters, and in Condition 2 for a target specified as one of a same-shape pair of letters. The exposure-time required for the same-name search was greater than that required for the same-shape search. In Exp III, accuracy of search was compared in the same-shape and same-name conditions with a control condition. The target in this control condition was specified as one of a pair of letters not sharing a name or any special shape. 12 Ss searched 6-item displays and 12 Ss searched 12-item displays for a pre-specified target letter. Results confirm the difference detected in Exp II, but they do not show any difference between performance in the same-name condition and in the control condition. It is suggested that some focal processing is required for the development of a sufficiently detailed level of visual representation to allow for naming. (French summary) (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fast priming during eye fixations in reading.

Near-threshold primes were "flashed" in a target location prior to the onset of a target word while Ss read. The type and duration of the prime were manipulated. In Exp 1, identical, related, and unrelated primes were presented for 60, 45, or 30 msec from onset of an eye fixation. The prime was then replaced with the target word, which remained in place while Ss finished reading the sentence. Fixation time on the target word was measured. Exp 2 replicated Exp 1, with 2 exceptions: A random letter string replaced the identical prime condition, and prime durations of 39, 30, or 21 msec were used. In both experiments, significant priming effects (related vs unrelated) were obtained when the prime was presented for 30 msec. Results are discussed with regard to subliminal priming effects. Applications to the study of word recognition processes are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of context manipulation on memory and reversal learning in rats with hippocampal lesions.

Conducted 3 experiments with 83 male Long-Evans rats to investigate (a) the memory of hippocampus-damaged Ss, and (b) their ability to modify response strategies in relation to the influence of familiar contextual cues. In Exp I, groups of hippocampal and control Ss learned a simultaneous discrimination habit and were subsequently tested for its retention under variable contextual conditions. All groups recalled the discrimination response to an equally high level when testing conditions were constant throughout, but the hippocampal group showed impaired memory when contextual stimuli at recall testing did not conform to those of original learning. Results of Exp II indicate that the hippocampal impairment was not simply the result of introducing novel stimuli. In Exp III, Ss were administered a reversal learning task with contextual stimuli varied between the 2 tests. The typically observed impairment of hippocampal Ss on this task was reduced by contrasting contextual conditions. Results are seen to support a context-retrieval interpretation of hippocampal function. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Transient structures": the effects of practice and distractor grouping on within-dimension conjunction searches

It has been stated that whereas between-dimension (color x orientation) conjunctions can be searched in a "parallel" fashion, within-dimension (color x color) conjunctions are necessarily searched in a "serial self-terminating" fashion (Wolfe et al., 1990). We explored the effects of practice (within 1-h experimental session) and distractor grouping on within-dimension conjunction search tasks. In Experiments 1 and 3, the stimuli were rectangles formed by two adjacent squares; in Experiment 2, the stimuli were plus signs formed by two segments and an intersection. In Experiments 1 and 2, observers were assigned to one of two experimental conditions: In one, all the distractors shared a simple feature (the color blue); in the other, distractors did not share that simple feature. In the first condition, search became more efficient with practice and observers' performance was characterized by a shallow reaction time (RT) x set size slope; in the second condition, observers' performance did not improve as much with practice. We propose that the differential effects of practice between these two experimental conditions can be explained in terms of distractor grouping induced by the shared color of the distractors. Experiment 3 showed that, with practice, a shallow RT x set size slope characterized observers' search for a color x color target among four different distractors that shared a common color. The present results contradict a main tenet of some current visual search models--namely, that within-dimension conjunctions cannot be searched in parallel, and question the validity of using RT x set size slope functions to distinguish between preattentive versus attentive search.