Immediate memory spans in dementia

Spatial span (Corsi's block-tapping test) and verbal spans for digits (Wechsler Digits Forward Test) and for words were measured in 30 normal subjects and in 51 demented patients, divided into two groups (mildly demented and severely demented) according to selective clinical and neuropsychological criteria. Statistical analysis showed significant differences among the three groups for spatial span. By contrast, controls' and mildly demented patients' performances on both verbal spans were not significantly different. These findings are discussed in the light of theory about working memory.     

Attention switching and working memory spans

Barrouillet and Camos () concluded from their developmental study on working memory that when performing complex span tasks, individuals maintain memory items by switching rapidly their attention from processing to storage while performing the concurrent task. Thus, a processing component that would require a continuous attentional focusing should have a highly detrimental effect on span. The present study verifies two predictions issuing from this hypothesis by comparing the classical self‐paced reading and operation span tasks with new computer‐paced tasks in adults. First, any increase in the pace at which the processing component of a working memory span task has to be performed impedes switching and then leads to lower spans. Second, when presented at a fast pace, even simple activities such as reading letters or adding and subtracting 1 to small numbers have an effect on spans as detrimental as complex activities like reading and understanding sentences or solving complex equations.     

Configurational information in face perception

A new facial composites technique is demonstrated, in which photographs of the top and bottom halves of different familiar faces fuse to form unfamiliar faces when aligned with each other. The perception of a novel configuration in such composite stimuli is sufficiently convincing to interfere with identification of the constituent parts (experiment 1), but this effect disappears when stimuli are inverted (experiment 2). Difficulty in identifying the parts of upright composites is found even for stimuli made from parts of unfamiliar faces that have only ever been encountered as face fragments (experiment 3). An equivalent effect is found for composites made from internal and external facial features of well-known people (experiment 4). These findings demonstrate the importance of configurational information in face perception, and that configurations are only properly perceived in upright faces.     

Configurational effects in visual information processing

These experiments show that the perceptual organization of a multielement display affects both the speed and accuracy with which a target letter in it is detected. The first two experiments show that a target is detected more poorly if it is arranged in good form (a perceptual Gestalt) with noise elements than if it is not. This effect is not confounded with target-noise proximity or display size, and it holds for stimuli terminated by the subject’s response as well as for stimuli of very brief duration. Increasing the number of noise elements can actually improve performance if the added noise elements increase the degree to which the noise elements form perceptual groups separately from the target. A third experiment tries out a new method for scaling the perceptual structure of an array, and it shows that the main features of the first two experiments can be predicted from the scaled perceptual structure of the arrays they used.     

A comparison of backward and forward spatial spans

The standard Corsi blocks task is frequently used to measure the capacity of visuospatial working memory, but the implications of the use of both forward and backward recall are still unclear. In the present study, we showed that the backward Corsi task is particularly powerful in discriminating between low- and high-spatial-ability individuals and involves different processes from those involved in the forward task. From a sample of 425 participants we selected one group of 20 high-spatial-ability participants and one of 20 low-spatial-ability participants. The results demonstrated that a backward spatial span offers specific information not available from a forward spatial span, and that there was no facilitation due to a descending format. In particular, in the low-spatial-ability group, performance was generally poorer, but backward Corsi recall was lower than forward recall, and participants did not show any advantage following the descending presentation format—which in some contexts is considered to reduce proactive interference. We conclude that the backward Corsi task has specific value and that the assumption of fully parallel verbal and visuospatial working-memory systems can lead to a variety of misunderstandings.     

A comparison of backward and forward spatial spans

The standard Corsi blocks task is frequently used to measure the capacity of visuospatial working memory, but the implications of the use of both forward and backward recall are still unclear. In the present study, we showed that the backward Corsi task is particularly powerful in discriminating between low- and high-spatial-ability individuals and involves different processes from those involved in the forward task. From a sample of 425 participants we selected one group of 20 high-spatial-ability participants and one of 20 low-spatial-ability participants. The results demonstrated that a backward spatial span offers specific information not available from a forward spatial span, and that there was no facilitation due to a descending format. In particular, in the low-spatial-ability group, performance was generally poorer, but backward Corsi recall was lower than forward recall, and participants did not show any advantage following the descending presentation format—which in some contexts is considered to reduce proactive interference. We conclude that the backward Corsi task has specific value and that the assumption of fully parallel verbal and visuospatial working-memory systems can lead to a variety of misunderstandings.     

Reaction time to letter name or letter case

Subjects were shown two letters from the set BDGbdg. In one condition, subjects were required to decide whether or not the letters had the same name. In the other condition, subjects decided whether or not the two letters were presented in the same case. Reaction times were always faster when the two letters on a given trial were physically identical. However, there was no difference in the speed of a name match or a case match when the two letters were not physically identical. Since subjects could have based a case match on the presence or absence of a single feature — a protruding vertical line — it was concluded that subjects are not able to selectively attend to a single visual feature in order to identify a letter. Rather, a subject analyzes several features in parallel in order to arrive at a simultaneous decision about a letter's name or case.     

Effect of age on forward and backward digit spans

Abstract

A number of studies has suggested that aging is characterized by a decline in the central executive while the automatic processes (in particular operations by the phonological loop) remain intact. According to interpretation, age differences should be minimal in verbal forward digit span while they should be more important in backward verbal digit span. A sample of 1,000 subjects with ages ranging from 16 years to 79 years was used to test this hypothesis. the results show no significant effect of age on the difference between digit span forward and backward. the theoretical implications of these results are discussed.     

Time constraints and resource sharing in adults' working memory spans

This article presents a new model that accounts for working memory spans in adults, the time-based resource-sharing model. The model assumes that both components (i.e., processing and maintenance) of the main working memory tasks require attention and that memory traces decay as soon as attention is switched away. Because memory retrievals are constrained by a central bottleneck and thus totally capture attention, it was predicted that the maintenance of the items to be recalled depends on both the number of memory retrievals required by the intervening treatment and the time allowed to perform them. This number of retrievals:time ratio determines the cognitive load of the processing component. The authors show in 7 experiments that working memory spans vary as a function of this cognitive load.     

Priming of abstract letter identities in the letter match task

Previous studies of letter recognition have not found priming for abstract letter identities. We used a task that required participants to decide whether a target is the same or different from a reference letter presented in opposite case, which avoids the shortcomings of tasks used in previous studies. We found robust priming effects in this task, which were the same size for letter pairs that have similar visual features across case (e.g., c/C, x/X) and dissimilar features (e.g., a/A, b/B). Also, the pattern of priming was the same whether the prime was in the same or different case as the reference. We take these findings as evidence that abstract letter identities support priming in this task. We suggest that the same–different match task is a useful tool for studying representations used to support masked priming in letter recognition and with other stimuli with limited set size.     

The independence of letter identity and letter doubling in reading

The ability to read requires processing the letter identities in the word and their order, but it is by no means obvious that our long-term memory representations of words spellings consist of only these dimensions of information. The current investigation focuses on whether we process information about another dimension—letter doubling (i.e., that there is a double letter in WEED)—independently of the identity of the letter being doubled. Two experiments that use the illusory word paradigm are reported to test this question. In both experiments, participants are more likely to misperceive a target word with only singleton letters (e.g., WED) as a word with a double (e.g., WEED) when the target is presented with a distractor that contains a different double letter (e.g., WOOD) than when the distractor does not contain a double letter (e.g., WORD). This pattern of results is not predicted by existing computational models of word reading but is consistent with the hypothesis that written language separately represents letter identity and letter doubling information, as previously shown in written language production. These results support a view that the orthographic representations that underlie our ability to read are internally complex and suggest that reading and writing rely on a common level of orthographic representation.     

Priming of abstract letter identities in the letter match task

Previous studies of letter recognition have not found priming for abstract letter identities. We used a task that required participants to decide whether a target is the same or different from a reference letter presented in opposite case, which avoids the shortcomings of tasks used in previous studies. We found robust priming effects in this task, which were the same size for letter pairs that have similar visual features across case (e.g., c/C, x/X) and dissimilar features (e.g., a/A, b/B). Also, the pattern of priming was the same whether the prime was in the same or different case as the reference. We take these findings as evidence that abstract letter identities support priming in this task. We suggest that the same-different match task is a useful tool for studying representations used to support masked priming in letter recognition and with other stimuli with limited set size.     

Knowing letter names and learning letter sounds: a causal connection

Two experiments tested the common assumption that knowing the letter names helps children learn basic letter-sound (grapheme-phoneme) relation because most names contain the relevant sounds. In Experiment 1 (n=45), children in an experimental group learned English letter names for letter-like symbols. Some of these names contained the corresponding letter sounds, whereas others did not. Following training, children were taught the sounds of these same "letters." Control children learned the same six letters, but with meaningful real-word labels unrelated to the sounds learned in the criterion letter-sound phase. Differences between children in the experimental and control groups indicated that letter-name knowledge had a significant impact on letter-sound learning. Furthermore, letters with names containing the relevant sound facilitated letter-sound learning, but not letters with unrelated names. The benefit of letter-name knowledge was found to depend, in part, on skill at isolating phonemes in spoken syllables. A second experiment (n=20) replicated the name-to-sound facilitation effect with a new sample of kindergarteners who participated in a fully within-subject design in which all children learned meaningless pseudoword names for letters and with phoneme class equated across related and unrelated conditions.