Multiple resources in divided attention: a cross-modal test of the independence of hemispheric resources

Dual-task methodology was used to assess a multiple-resources account of information processing in which each cerebral hemisphere is assumed to have access to its own finite amount of attentional resources. A visually presented verbal memory task was paired with an auditory tone memory task, and subjects were paid to emphasize one task more than the other. When subjects were trying to remember tones presented to the right ear, they could trade performance between tasks as a function of the emphasis condition, whereas on left-ear trials they could not. In addition, a control session indicated that stimuli presented to the unattended ear demanded processing resources, even when it was to the detriment of performance. The data support the assumption of independence between the hemispheres' resource supplies.     

Role of multiple resources in predicting time-sharing efficiency: evaluation of three workload models in a multiple-task setting

The goal of our study was to assess the validity of the assumptions underlying three prominent workload models: the Time-Line Analysis and Prediction workload model (Parks & Boucek, 1989), the VACP workload model (Aldrich, Szabo, & Bierbaum, 1989), and the W/INDEX model (North & Riley, 1989). Sixteen subjects flew a low-fidelity flight simulation. Subjects were required to perform a two-axis tracking task, a concurrent visual-monitoring task, and a discrete decision task. The decision task had 16 variations defined by two levels on each of the following dimensions: input modality (visual vs. auditory), processing code (spatial vs. verbal), difficulty (easy vs. hard), and response modality (manual vs. voice). Dual-task costs were found only for the tracking task. The tracking data were then analyzed using two approaches: a traditional analysis of variance (ANOVA) and a correlational analysis of tracking performance versus model predictions. The ANOVA revealed that performance on the tracking task was better when the concurrent decision task was responded to vocally and was easy. Input modality and processing code of the concurrent decision task had no significant effect on tracking performance. The correlational analysis was used to evaluate each of the three models, to determine what features were responsible for improving the models' fit, and to compare their performance with a pure time-line model that makes no multiple-resource assumptions. All three models did a good job of predicting variance between experimental conditions, accounting for between 56% and 84% of the variance in our data and between 10% and 40% of an earlier data set. Different features of each model that affect the fit are then discussed. We conclude that it is important for models to retain a multiple-resource coding, although the best features of that coding remain to be determined. Coding tasks by their demand level appears to be less critical.     

Validation of a pictorial recall test in three visual formats.

This study describes the validation of a visual recall test which was constructed using three different levels of visual complexity, line drawing, monochrome photographic, and color photographic. For a sample of 111 college students, the test was significantly correlated (.42 and .92) with two recognized tests of visual memory.     

On coding the position of letters in words: a test of two models

Open-bigram and spatial-coding schemes provide different accounts of how letter position is encoded by the brain during visual word recognition. Open-bigram coding involves an explicit representation of order based on letter pairs, while spatial coding involves a comparison function operating over representations of individual letters. We identify a set of priming conditions (subset primes and reversed interior primes) for which the two types of coding schemes give opposing predictions, hence providing the opportunity for strong scientific inference. Experimental results are consistent with the open-bigram account, and inconsistent with the spatial-coding scheme.     

Sex differences in memory estimates for pictures and words with multiple recall trials

Undergraduate students (23 men and 23 women) provided memory performance estimates before and after each of three recall trials involving 80 stimuli (40 pictures and 40 words). No sex differences were found across trials for the total recall of items or for the recall of pictures and words separately. A significant increase in recall for pictures (not words) was found for both sexes across trials. The previous results of Ionescu were replicated on the first and second recall trials: men underestimated their performance on the pictures and women underestimated their performance on the word items. These differences in postrecall estimates were not found after the third recall trial: men and women alike underestimated their performance on both the picture and word items. The disappearance of item-specific sex differences in postrecall estimates for the third recall trial does not imply that men and women become more accurate at estimating their actual performance with multiple recall trials.     

Hypermnesia for pictures: Incremental memory for pictures but not words in multiple recall trials

Two studies are reported on multiple forced recall following a single visual presentation of a sequence of pictures or words. In both experiments, a hypermnesic memory function (in which performance improved with repeated recall) was obtained for pictures, while a flat, nonincremental function was obtained for words. Interpolation of intervals of thinking between recall trials further enhanced hypermnesia for pictorial items. Retrieval, whether overt (recall trials) or covert (thinking), apparently produces increased net recovery of pictures but not words.     

The effect of increased incentive on free recall by learning-disabled and nondisabled children

Immediate free recall by learning-disabled and nondisabled children was compared under two incentive conditions. Recall of the first few words of each list by disabled children and younger nondisabled children was lower than that by older nondisabled children, and receiving a monetary reward increased early list item recall by older disabled and nondisabled learners. These findings suggest that elaborative encoding processes, such as rehearsal, are impaired in younger disabled and nondisabled children and that receiving a reward increased elaborative encoding by older children. Similar recall of the last few list items by all groups suggests that attention and immediate memory are comparable in disabled and nondisabled children of different ages. Receiving a reward increased recall of the last few list items by younger disabled and nondisabled children, suggesting that a reward increased attention, immediate memory, or both, in these groups. Because receiving a reward increased recall equally in all groups, lower motivation did not appear to be responsible for the lower recall by younger nondisabled children and learning-disabled children.     

Name and face matching in one or two visual fields: a test of models of hemispheric specialization

In two experiments a name and a face (each male or female) were simultaneously flashed to either the same or opposite visual fields (left or right), for matching congruent (same sex) or incongruent (opposite sex), to test the predictions of various models of hemispheric specialization. While overall best performance occurred with a face in the left visual field (LVF) and a name in the right visual field (RVF), and worst with the opposite configuration, the general pattern of results was incompatible with either a direct access model or an activational/attentional account. The results were, however, most compatible with the predictions of a semispecialized hemispheres account, whereby cerebral asymmetries are seen as relative rather than absolute, either hemisphere being capable of processing either kind of material (verbal or visuospatial), but to different levels of efficiency. However, despite the fact that the stimulus materials had previously been shown to produce stable and consistent lateral asymmetries in the predicted directions when presented in isolation, in the composite, integrative matching task the position of the name seemed to be the major determinant of the resultant asymmetries. It would seem therefore that when such stimuli are to be cross matched, either left hemisphere (language) processes somehow dominate right hemisphere (visuospatial) processing (though not in the way that would be predicted by a simple activational/attentional account) or the left hemisphere's greater capacity predominates.     

Two- versus three-alternative concurrent-chain schedules: a test of three models

Two experiments with pigeons used concurrent-chain procedures with variable-interval schedules as initial links and different delays to food as terminal links. Two schedules were present in all sessions, but a 3rd schedule was alternately present and absent in successive sessions. When the 3rd schedule delivered food with no terminal-link delay, the presence of this schedule led to an increase in preference for the schedule with the shorter terminal link of the 2 unchanged schedules. When the terminal-link delay for the 3rd schedule was 30 s, the presence of this schedule led to a decrease in preference for the schedule with the shorter terminal link of the 2 unchanged schedules. These results are inconsistent with the predictions of R. Grace's (1994) contextual-choice model, but they are consistent with 2 other mathematical models--delay-reduction theory and the hyperbolic value-added model.     

Production deficiencies in free recall: A comparison of hyperactive,learning-disabled,and normal children

Free recall of weakly categorizable words was compared in hyperactive (ADDH), reading-disabled, and normal boys. During a baseline trial, hyperactive boys recalled fewer words and showed less category organization than both reading-disabled and normal boys. Following a manipulation designed to encourage semantic encoding of words, hyperactive boys showed an immediate improvement in item recall and organization so that their free-recall performance was similar to that of reading-disabled and normal children. During later trials of a multiple-trial format, hyperactive boys recalled fewer words than did the reading-disabled and normal boys, despite maintaining equality in category organization. Rather than lacking the skill to use semantic organization as a strategy in free recall, hyperactive boys had difficulty in spontaneously generating the organizational strategy in response to instructions to remember and sustaining sufficient effort to task completion.     

Menatal addition: A test of three verification models

Three explanations of adults’ mental addition performance, a counting-based model, a direct-access model with a backup counting procedure, and a network retrieval model, were tested. Whereas important predictions of the two counting models were not upheld, reaction times (RTs) to simple addition problems were consistent with the network retrieval model. RT both increased with problem size and was progressively attenuated to false stimuli as the split (numerical difference between the false and correct sums increased. For large problems, the extreme level of split (13) yielded an RT advantage for false over true problems, suggestive of a global evaluation process operating in parallel with retrieval. RTs to the more complex addition problems in Experiment 2 exhibited a similar pattern of significance and, in regression analyses, demonstrated that complex addition (e.g., 14+12=26) involves retrieval of the simple addition components (4+2=6). The network retrieval/decision model is discussed in terms of its fit to the present data, and predictions concerning priming facilitation and inhibition are specified. The similarities between mental arithmetic results and the areas of semantic memory and mental comparisons indicate both the usefulness of the network approach to mental arithmetic and the usefulness of mental arithmetic to cognitive psychology.     

Recognition failure of recallable words: free and cued recall compared

The experiment reported was conducted with the purpose of studying whether the phenomenon of recognition failure of recallable words would hold for a paradigm which involves a free recall test rather than a cued recall test used in previous research. The 3×2 design used comprised two between-subjects factors: the subjects were instructed that a recognition test, a cued recall test, or a free recall test would follow the study trial, but the actual test sequence given was recognition followed by cued recall, or recognition followed by free recall. The results demonstrate that cases of recognition failure of recallable words do occur in all six conditions, but the amount of recognition failure for the recognition-free recall test sequence was less than that predicted from the Tulving & Wiseman (1975) function. In line with previous research the data for the recognition-cued recall test sequence showed the amount of recognition failure that was predicted by this function.     

Sex task and processing strategy effects in hemispheric alpha asymmetries for the recall and recognition of arousal words: results from perceptual and motor tasks in males and females

Hemispheric alpha asymmetries of males and females were observed during perceptual and motor tasks requiring recall and recognition of words controlled for level of arousal (positive, negative, and neutral). Verbal reports of individual processing strategy were collected and analyzed relative to hemispheric alpha ratios. Results showed greater alpha suppression in the left relative to right hemisphere for recall as compared to recognition tasks and for word presentation when contrasted with motor conditions. High positive correlations were found between narrative report of processing strategy and hemispheric alpha data. A separate analysis revealed that seven subjects identified as highly analytic processors showed greater alpha suppression in the left relative to right hemisphere across tasks, conditions, and stimuli than did seven highly visual processors who, in contrast, demonstrated greater right hemispheric alpha suppression. Task difficulty and individual differences in processing style that modify cerebral laterality effects are discussed.     

Left-side infant holding: a test of the hemispheric arousal-attentional hypothesis

When asked to hold a young infant in their arms, most adults hold on the left side (Harris, 1997). In a prior study, we found the same bias when we asked adults merely to imagine holding an infant in their arms (Harris, Almerigi, & Kirsch, 1999). It has been hypothesized that the left-side bias is the product of right-hemisphere arousal accompanying certain aspects of the act, causing attention to be driven to the contralateral, or left, side of personal space. Left-side holding, whether actual or imagined, thus would be consistent with the direction to which the holder's attention has been endogenously directed. We tested this hypothesis by giving 250 college students the "imagine-holding" task and then, as an independent measure of lateralized hemispheric arousal, a 34-item Chimeric Faces Test (CFT). On the "imagine" test, a significant majority reported a left-side hold, and, on the CFT, left-side holders had a significantly stronger left-hemispace bias than right-side holders, although both left- and right side holders had left-hemispace CFT biases. The results thus support the attentional-arousal hypothesis but indicate that other factors are contributing as well.     

Examining the relationship between free recall and immediate serial recall: The serial nature of recall and the effect of test expectancy

In two experiments, we examined the relationship between free recall and immediate serial recall (ISR), using a within-subjects (Experiment 1) and a between-subjects (Experiment 2) design. In both experiments, participants read aloud lists of eight words and were precued or postcued to respond using free recall or ISR. The serial position curves were U-shaped for free recall and showed extended primacy effects with little or no recency for ISR, and there was little or no difference between recall for the precued and the postcued conditions. Critically, analyses of the output order showed that although the participants started their recall from different list positions in the two tasks, the degree to which subsequent recall was serial in a forward order was strikingly similar. We argue that recalling in a serial forward order is a general characteristic of memory and that performance on ISR and free recall is underpinned by common memory mechanisms.     

Recognizing words and pictures in sentence contexts: a test of lexical modularity

Words or pictures completed sentence fragments to form coherent or incoherent sentences. Subjects made lexical decisions about words and object decisions about pictures. Modality was blocked in Experiment 1 and mixed in Experiment 2. In both experiments there were similar effects of context for words and pictures, contrary to the hypothesis that lexical priming produces the sentence context effect. Mixed conditions produced longer response latencies than blocked conditions but did not interact with the context effect. The finding of no interaction between the effect of context and the mixed-blocked manipulation, supports a version of lexical modularity in which context effects arise as a function of post-access integration processing.     

Immediate serial recall of words and nonwords: Tests of the retrieval-based hypothesis

In two experiments, the immediate serial recall of lists of words or nonwords was investigated under quiet and articulatory suppression conditions. The results showed better item recall for words but better order recall for nonwords, as measured with proportion of order errors per item recalled. Articulatory suppression hindered the recall of item information for both types of lists and of order information for words. These results are interpreted in light of a retrieval account in which degraded phonological traces must undergo a reconstruction process calling on long-term knowledge of the tobe-remembered items. The minimal long-term representations for nonwords are thought to be responsible for their lower item recall and their better order recall. Under suppression, phonological representations are thought to be minimal, producing trace interpretation problems responsible for the greater number of item and order errors, relative to quiet conditions. The very low performance for nonwords under suppression is attributed to the combination of degraded phonological information and minimal long-term knowledge.