Visuospatial Working Memory Abilities Research Articles

Executive function and spatial abilities in physically active children: an explorative study

BackgroundRegular physical activity has consistently shown promise in improving cognitive functioning among children. However, there is a shortage of comprehensive studies that delve into these benefits across various cognitive domains. This preliminary investigation aimed to discern potential disparities in cognitive performance between active and sedentary children, with a specific focus on inhibitory control, cognitive flexibility, and visuo-spatial working memory abilities.MethodsThe study employed a cross-sectional design encompassing 26 children (mean age 9.53 ± 2.20 years), categorized into two groups: Active and Sedentary. Executive functions were assessed using the NEPSY-II, while visuo-spatial working memory abilities were evaluated through the table version of the Radial Arm Maze (table-RAM) task. All outputs were analyzed with One-way ANOVAS or Kruskal–Wallis Tests to assess differences between Active and Sedentary children in both executive functioning and visuo-spatial working memory processes.ResultsThe findings revealed that the Active group outperformed the sedentary group in inhibitory control (F1,23 = 4.99, p = 0.03*), cognitive flexibility (F1,23 = 5.77, p = 0.02*), spatial span (F1,23 = 4.40, p = 0.04*), and working memory errors (F1,23 = 8.59, p = 0.01**). Both spatial span and working memory errors are parameters closely associated with visuo-spatial working memory abilities.ConclusionsAlthough preliminary, these results offer evidence of a positive link between physical activity and cognitive functioning in children. This indicates the importance of promoting active behaviors, especially within educational environments.

Visuospatial working memory abilities in children analyzed by the bricks game task (BGT)

The study of the development of visuospatial memory processes is useful for devising personalized educational interventions as well as for understanding the changes in cognitive functioning in an era characterized by technological progress. The present research is aimed at investigating spatial working memory ability in children that attended the first three years of primary school by means of the Brick Game Task (BGT), a novel visuospatial working memory test. BGT is a small-scale ecological test inspired by behavioral walking tasks with nine white bricks in different spatial configurations as well as to Corsi Block-Tapping test.228 Italian children (121 F; mean age: 7.22 ± 1.18) were assigned to three groups based on the primary school class attended: Group 1 (N = 85; 40 F; mean age 6.18 ± .5), Group 2 (N = 61; 36 F; mean age 7.2 ± .83), and Group 3 (N = 82; 44 F; mean age 8.32 ± .94). All participants were asked to complete the Digit Span test, the Corsi Block-Tapping test, and to explore the three spatial configurations of the BGT with the form of Matrix, M-BGT, Cluster, CL-BGT, Cross, CR-BGT.MANOVA revealed a main significant effect for Group (F12,434 = 15.06; p < .0001) indicating that the group of older obtained a better global executive performance than 1 and 2 groups. Multiple linear regression indicated that Corsi Block-Tapping test performance and Age significantly predicted the M-BGT score. Moreover, Corsi Block-Tapping test and Digit Span significantly predicted the CL-BGT performance, showing how a higher score results in a better CL- BGT performance. Finally, Corsi Block-Tapping test, Digit Span, and Age were positively associated with the CR- BGT performance. The present findings evidenced that novel BGT is a sensible visuospatial working memory task suggesting thus its use to assess the children’s executive performance in ecological way. These results open to the development of personalized educational interventions.

Visuospatial working memory capacity moderates the relationship between anxiety and OCD related checking behaviors.

Compulsive checking behavior is the most prevalent compulsive behavior in patients with obsessive-compulsive disorder (OCD). While some studies have shown that anxiety and executive function influence compulsive checking behavior, the relationship between these constructs is inconclusive. Hence, we sought to explore the interplay between executive function, anxiety and compulsive checking behavior. 47 healthy participants (HC) and 51 patients with OCD participated in the study. Symptoms and emotional states were assessed using the Yale-Brown Obsessive Compulsive Scale, the Obsessive-Compulsive Inventory-Revised, the Beck Anxiety Inventory, and the Beck Depression Inventory. Participants also completed three tests of neuropsychological functioning: the Stop Signal Task, the Spatial working memory Task, and the Wisconsin card sorting test. We analyzed the relationships between anxiety, executive function, and compulsive checking symptoms. Patients with OCD showed significantly greater anxiety (p < 0.001) and impairments in visuospatial working memory function (p = 0.030) compared to HC participants, while inhibition and set-shifting were not significantly different between the two groups. Visuospatial working memory was negatively related to compulsive checking behavior (p = 0.016). Visuospatial working memory also played a moderating role in the positive relationship between anxiety and compulsive checking behavior (β = -0.281, p = 0.022). Anxiety symptoms play an important role in explaining compulsive checking behavior in patients with OCD who have relatively weak visuospatial working memory ability. These findings provide a foundation for further research regarding the roles of emotion and cognitive inflexibility in compulsive checking behavior in patients with OCD.

Visuospatial working memory abilities and spontaneous sensations perception

Aim: Body awareness arises when attending to and maintaining awareness of visuospatial body representations. By the same token, focussing on representations transfers them to working memory. Body awareness and working memory seemingly rely on similar processes and recruit common parietal areas involved in perception. Therefore, we asked whether visuospatial working memory abilities would define individual differences in the perception of spontaneous sensations (SPS), i.e., bodily sensations perceived in the absence of triggers (e.g., tactile stimulation or movement), when attending to the body. Method: Participants completed two visuospatial working memory tasks to assess various mechanisms: (i) the decay of representations was assessed through a Brown-Peterson task in which the delay between the memorandum presentation and its recall was manipulated, and (ii) the impact of distractors’ interference and cognitive load (i.e., complexity) on recall performances were assessed through a complex span task that required the processing of distractors while maintaining a memorandum. A standard SPS task involving localization and characterization of SPS perceived on the hands was completed afterwards. Results: Low performance due to decay, distractors’ interference and cognitive load in visuospatial working memory was associated with a decrease in the frequency of SPS. Additionally, low performance due to distractors’ cognitive load predicted a decrease in the perception of surface-type sensations, and high performance despite distractors’ interference led to a better perception of SPS on less sensitive areas of the hand. Conclusion: We discuss how visuospatial working memory processes might contribute to body awareness and perceptual distortions of the body.

Developmental trajectories of strategy use in children with mathematical anxiety

The main goal of the present study was to explore strategy selection in high mathematical anxiety (MA) individuals, and to test the role of development in the selection of strategy. We tested 2nd, 3rd and 5th graders with high or low MA in simple and complex addition problems. Participants first solved the problems and were then asked to report the strategy that they used. During elementary school, typically developing children change strategy use. In the first years backup strategies of counting are very frequent, but with maturation and schooling, they can shift to memory- based strategies. Hence, we tested finger counting and advanced memory based strategies in high MA children. In finger counting, high MA children showed developmental delay. For example, in the third grade, low MA children stopped using finger counting, while high MA participants continued to use it. However, in the case of advanced strategy use, we found a different pattern: regardless of age, high MA children used less advanced strategies than low MA participants. Moreover, usage of advanced memory based strategies was modulated by visuospatial working memory abilities in the two groups. The present results suggest that the MA participant has atypical developmental trajectories in strategy use.

Does learner cognition count on modality? Working memory and L2 morphosyntactic achievement across oral and written tasks

AbstractThis study investigates how working memory (WM) abilities are implicated in second language (L2) learners’ (a) morphosyntactic achievement and (b) perceptions of required mental effort and task difficulty under oral versus written task modality conditions. Beginning-level learners of L2 Spanish completed two computerized focused tasks in which they produced output and received feedback in oral form (Speaking group) or written form (Writing group). Two grammatical structures varying in their relative level of salience were targeted. After each task, participants rated their perceptions of mental effort required and task difficulty. Production and written and aural acceptability judgment tasks were employed to measure immediate and sustained L2 morphosyntactic achievement. Executive, phonological, and visuospatial WM abilities were gauged using automated operation span, nonword recognition, and forward Corsi block-tapping tasks, respectively. Regression analyses revealed that WM capacity was predictive of L2 morphosyntactic outcomes and task perception ratings in the Speaking group only. Specifically, phonological and visuospatial WM were associated with production and acceptability judgment performance accuracy, whereas executive WM was related to learners’ ratings of perceived mental effort. Differences were also observed based on the target structure.

Are morphological and structural MRI characteristics related to specific cognitive impairments in neurofibromatosis type 1 (NF1) children?

NF1 children have cognitive disorders, especially in executive functions, visuospatial, and language domains, the pathophysiological mechanisms of which are still poorly understood. A correlation study was performed from neuropsychological assessments and brain MRIs of 38 NF1 patients and 42 controls, all right-handed, aged 8-12 years and matched in age and gender. The most discriminating neuropsychological tests were selected to assess their visuospatial, metaphonological and visuospatial working memory abilities. The MRI analyses focused on the presence and location of Unidentified Bright Objects (UBOs) (1), volume analysis (2) and diffusion analysis (fractional anisotropy and mean diffusivity) (3) of the regions of interest including subcortical structures and posterior fossa, as well as shape analysis of subcortical structures (4). The level of attention, intelligence quotient, age and gender of the patients were taken into account in the statistical analysis. Then, we studied how diffusion and volumes parameters were associated with neuropsychological characteristics in NF1 children. NF1 children present different brain imaging characteristics compared to the control such as (1) UBOs in 68%, (2) enlarged total intracranial volume, involving all subcortical structures, especially thalamus, (3) increased MD and decreased FA in thalamus, corpus callosum and hippocampus. These alterations are diffuse, without shape involvement. In NF1 group, brain microstructure is all the more altered that volumes are enlarged. However, we fail to find a link between these brain characteristics and neurocognitive scores. While NF1 patients have obvious pathological brain characteristics, the neuronal substrates of their cognitive deficits are still not fully understood, perhaps due to complex and multiple pathophysiological mechanisms underlying this disorder, as suggested by the heterogeneity observed in our study. However, our results are compatible with an interpretation of NF1 as a diffuse white matter disease.

Executive functions in kindergarten children at risk for developmental coordination disorder

Executive functioning (EF) is a key cognitive process for development. Little is known about EF in Kindergarten children at risk for developmental coordination disorder (DCD), despite this age being one of the most critical and intensive period of motor and cognitive development. In our investigation we compared EF in kindergarten children at risk for DCD with Typically Developing (TD) children. Participants were 36 Italian children, 18 at risk for DCD (9 boys and 9 girls) who had a mean age of 4.6 years and 18 TD (9 boys and 9 girls) who had a mean age of 4.6. Executive functions were measured by tasks targeting cold executive functioning (working memory, fluency, inhibitory control) and two assessments of hot executive functioning (Snack Delay and Gift Wrap). Significant differences were found between children at risk for DCD and TD children on cold EF tasks of visuo-spatial working memory abilities, fluency and inhibitory control, but not on hot EF tasks. The findings suggest that it is advisable to implement preschool cognitively challenging physical activities programmes.

New protocol for dissociating visuospatial working memory ability in reaching space and in navigational space.

Several studies have demonstrated that the processing of visuospatial memory for locations in reaching space and in navigational space is supported by independent systems, and that the coding of visuospatial information depends on the modality of the presentation (i.e., sequential or simultaneous). However, these lines of evidence and the most common neuropsychological tests used by clinicians to investigate visuospatial memory have several limitations (e.g., they are unable to analyze all the subcomponents of this function and are not directly comparable). Therefore, we developed a new battery of tests that is able to investigate these subcomponents. We recruited 71 healthy subjects who underwent sequential and simultaneous navigational tests by using an innovative sensorized platform, as well as comparable paper tests to evaluate the same components in reaching space (Exp. 1). Consistent with the literature, the principal-component method of analysis used in this study demonstrated the presence of distinct memory for sequences in different portions of space, but no distinction was found for simultaneous presentation, suggesting that different modalities of eye gaze exploration are used when subjects have to perform different types of tasks. For this purpose, an infrared Tobii Eye-Tracking X50 system was used in both spatial conditions (Exp. 2), showing that a clear effect of the presentation modality was due to the specific strategy used by subjects to explore the stimuli in space. Given these findings, the neuropsychological battery established in the present study allows us to show basic differences in the normal coding of stimuli, which can explain the specific visuospatial deficits found in various neurological conditions.

Intrinsic motivation and academic performance in school-age children born extremely preterm: The contribution of working memory

Intrinsic motivation is associated with better academic performance. Working memory abilities may contribute to this association, especially in children at risk for learning and academic difficulties such as those born extremely preterm. This study examined whether verbal and visuo-spatial working memory abilities mediate the relationship between intrinsic motivation for school learning (mastery, challenge and curiosity) and academic performance (word reading, spelling and mathematics) in 7-year old extremely preterm or extremely low birth weight children (n = 91). Structural equation modeling revealed verbal short-term memory to mediate associations between aspects of intrinsic motivation and literacy performance. Positive associations between mastery and verbal short-term memory, reading and spelling, and a positive association between challenge and mathematics performance were also identified. These findings highlight potential pathways linking intrinsic motivation for school learning, working memory, and academic achievement in early school-age children at risk of academic impairments. Examination of individual characteristics such as motivation and cognitive skills is important for understanding factors that shape children's learning and performance.

Visuospatial working memory assessment using a digital tablet in adolescents with attention deficit hyperactivity disorder

Background and objectiveAttention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder hypothesized to involve impaired visuospatial working memory (VSWM). However, there are few studies utilizing neuropsychological tests to measure VSWM in ADHD adolescents. The Rey–Osterrieth complex figure test (ROCF) is commonly used as a neuropsychological test to assess visuospatial working memory for individuals with ADHD. We assessed working memory using the ROCF test on a digital Galaxy tablet with the technically new Gaussian filter method. MethodsThirty adolescents with ADHD and 30 healthy control adolescents were recruited for participation in the current study. All adolescents were assessed with K-WISC-IV, Children's depression inventory, and the Korean ADHD rating scale. All adolescents were asked to copy the ROCF from paper onto a Galaxy tablet screen using a wireless pen. ResultsThere was a significant difference in representative value of the deviation of the original images from template images (R-value) in copy and delayed recall between ADHD adolescents and healthy adolescents. There was no significant difference in R-value of immediate recall between ADHD adolescents and healthy adolescents. In all adolescents (ADHD and healthy) and ADHD adolescents, the R-value of copy was negatively correlated with visuospatial index and working memory index, and the R-value of delayed recall was negatively correlated with WMI. The R-value of copy and delayed recall was positively correlated with K-ARS in all adolescents and ADHD adolescents. ConclusionsADHD adolescents showed differences in the R-values of copy and delayed recall in the digital ROCF version compared to healthy adolescents. The digital ROCF assessment tool can represent different patterns of visuospatial working memory abilities in ADHD adolescents compared to healthy adolescents.

TEMA and Dot Enumeration Profiles Predict Mental Addition Problem Solving Speed Longitudinally.

Different math indices can be used to assess math potential at school entry. We evaluated whether standardized math achievement (TEMA-2 performance), core number abilities (dot enumeration, symbolic magnitude comparison), non-verbal intelligence (NVIQ) and visuo-spatial working memory (VSWM), in combination or separately, predicted mental addition problem solving speed over time. We assessed 267 children’s TEMA-2, magnitude comparison, dot enumeration, and VSWM abilities at school entry (5 years) and NVIQ at 8 years. Mental addition problem solving speed was assessed at 6, 8, and 10 years. Longitudinal path analysis supported a model in which dot enumeration performance ability profiles and previous mental addition speed predicted future mental addition speed on all occasions, supporting a componential account of math ability. Standardized math achievement and NVIQ predicted mental addition speed at specific time points, while VSWM and symbolic magnitude comparison did not contribute unique variance to the model. The implications of using standardized math achievement and dot enumeration ability to index math learning potential at school entry are discussed.

Executive functions predict conceptual learning of science.

We examined the relationship between executive functions and both factual and conceptual learning of science, specifically chemistry, in early adolescence. Sixty-three pupils in their second year of secondary school (aged 12-13years) participated. Pupils completed tasks of working memory (Spatial Working Memory), inhibition (Stop-Signal), attention set-shifting (ID/ED), and planning (Stockings of Cambridge), from the CANTAB. They also participated in a chemistry teaching session, practical, and assessment on the topic of acids and alkalis designed specifically for this study. Executive function data were related to (1) the chemistry assessment which included aspects of factual and conceptual learning and (2) a recent school science exam. Correlational analyses between executive functions and both the chemistry assessment and science grades revealed that science achievements were significantly correlated with working memory. Linear regression analysis revealed that visuospatial working memory ability was predictive of chemistry performance. Interestingly, this relationship was observed solely in relation to the conceptual learning condition of the assessment highlighting the role of executive functions in understanding and applying knowledge about what is learned within science teaching.

Brain structural substrates of cognitive procedural learning in alcoholic patients early in abstinence.

Procedural learning allows for the acquisition of new behavioral skills. Previous studies have shown that chronic alcoholism is characterized by impaired cognitive procedural learning and brain abnormalities affecting regions that are involved in the automation of new cognitive procedures in healthy individuals. The goal of the present study was to investigate the brain structural substrates of cognitive procedural learning in alcoholic patients (ALs) early in abstinence. Thirty-one ALs and 31 control participants (NCs) performed the Tower of Toronto task (4 daily learning sessions, each comprising 10 trials) to assess cognitive procedural learning. We also assessed episodic and working memory, executive functions, and visuospatial abilities. ALs underwent 1.5T structural magnetic resonance imaging. The initial cognitive phase was longer in the AL group than in the NC group, whereas the autonomous phase was shorter. In ALs, the longer cognitive phase was predicted by poorer planning and visuospatial working memory abilities, and by smaller gray matter (GM) volumes in the angular gyrus and caudate nucleus. ALs' planning abilities correlated with smaller GM volume in the angular gyrus. Cognitive procedural learning was impaired in ALs, with a delayed transition from the cognitive to the autonomous phase. This slowdown in the automation of the cognitive procedure was related to lower planning abilities, which may have hampered the initial generation of the procedure to be learned. In agreement with this neuropsychological finding, a persistent relationship was found between learning performance and the GM volumes of the angular gyrus and caudate nucleus, which are usually regarded as markers of planning and initial learning of the cognitive procedure.

How Does Experience Modulate Auditory Spatial Processing in Individuals with Blindness?

Comparing early- and late-onset blindness in individuals offers a unique model for studying the influence of visual experience on neural processing. This study investigated how prior visual experience would modulate auditory spatial processing among blind individuals. BOLD responses of early- and late-onset blind participants were captured while performing a sound localization task. The task required participants to listen to novel “Bat-ears” sounds, analyze the spatial information embedded in the sounds, and specify out of 15 locations where the sound would have been emitted. In addition to sound localization, participants were assessed on visuospatial working memory and general intellectual abilities. The results revealed common increases in BOLD responses in the middle occipital gyrus, superior frontal gyrus, precuneus, and precentral gyrus during sound localization for both groups. Between-group dissociations, however, were found in the right middle occipital gyrus and left superior frontal gyrus. The BOLD responses in the left superior frontal gyrus were significantly correlated with accuracy on sound localization and visuospatial working memory abilities among the late-onset blind participants. In contrast, the accuracy on sound localization only correlated with BOLD responses in the right middle occipital gyrus among the early-onset counterpart. The findings support the notion that early-onset blind individuals rely more on the occipital areas as a result of cross-modal plasticity for auditory spatial processing, while late-onset blind individuals rely more on the prefrontal areas which subserve visuospatial working memory.

Visuo–spatial working memory is an important source of domain-general vulnerability in the development of arithmetic cognition

The study of developmental disorders can provide a unique window into the role of domain-general cognitive abilities and neural systems in typical and atypical development. Mathematical disabilities (MD) are characterized by marked difficulty in mathematical cognition in the presence of preserved intelligence and verbal ability. Although studies of MD have most often focused on the role of core deficits in numerical processing, domain-general cognitive abilities, in particular working memory (WM), have also been implicated. Here we identify specific WM components that are impaired in children with MD and then examine their role in arithmetic problem solving. Compared to typically developing (TD) children, the MD group demonstrated lower arithmetic performance and lower visuo-spatial working memory (VSWM) scores with preserved abilities on the phonological and central executive components of WM. Whole brain analysis revealed that, during arithmetic problem solving, left posterior parietal cortex, bilateral dorsolateral and ventrolateral prefrontal cortex, cingulate gyrus and precuneus, and fusiform gyrus responses were positively correlated with VSWM ability in TD children, but not in the MD group. Additional analyses using a priori posterior parietal cortex regions previously implicated in WM tasks, demonstrated a convergent pattern of results during arithmetic problem solving. These results suggest that MD is characterized by a common locus of arithmetic and VSWM deficits at both the cognitive and functional neuroanatomical levels. Unlike TD children, children with MD do not use VSWM resources appropriately during arithmetic problem solving. This work advances our understanding of VSWM as an important domain-general cognitive process in both typical and atypical mathematical skill development.

Right-sided representational neglect after left brain damage in a case without visuospatial working memory deficits

Brain damaged patients suffering from representational neglect (RN) fail to report, orient to, or verbally describe contra-lesional elements of imagined environments or objects. So far this disorder has only been reported after right brain damage, leading to the idea that only the right hemisphere is involved in this deficit. A widely accepted account attributes RN to a lateralized impairment in the visuospatial component of working memory. So far, however, this hypothesis has not been tested in detail. In the present paper, we describe, for the first time, the case of a left brain damaged patient suffering from right-sided RN while imagining both known and new environments and objects. An in-depth evaluation of her visuospatial working memory abilities, with special focus on the presence of a lateralized deficit, did not reveal any abnormality. In sharp contrast, her ability to memorize visual information was severely compromised. The implications of these results are discussed in the light of recent insights in the neglect syndrome.

Attention Problems of Very Preterm Children Compared with Age-Matched Term Controls at School-Age

To clarify the severity, specificity, and neurocognitive underpinnings of attention problems in very preterm children. A sample of 66 preterm (<32 weeks gestation), mean (SD) age 7.5 (0.4) years, and 66 age-matched term controls participated. Symptoms of inattention were assessed using parent and teacher-rated questionnaires, and neurocognitive measures included speed and consistency in speed of information processing, lapses of attention (tau), alerting, orienting, and executive attention, as well as verbal and visuospatial working memory. Group differences were investigated using ANOVA, and Sobel tests were used to clarify the mediating role of neurocognitive impairments on attention problems. There was a large decrease in visuospatial working memory abilities (P < .001, d = .87), and medium increases in tau (P = .002, d = 0.55) as well as parent and teacher ratings of inattention (range d = 0.40-0.56) in very preterm children compared with term peers. Tau and visuospatial working memory were significant predictors of parent (R(2) = .161, P < .001 and R(2) = .071, P = .001; respectively) and teacher (R(2) = .152, P < .001 and R(2) = .064, P = .002; respectively) ratings of inattention, and completely explained the effects of very preterm birth on attention problems. Increased lapses of attention and poorer visuospatial working memory fully account for the attention problems in very premature children at school-age.

Neonatal Cerebral Abnormalities and Later Verbal and Visuospatial Working Memory Abilities of Children Born Very Preterm

As part of a prospective, longitudinal study, 103 very preterm children underwent structural magnetic resonance (MR) imaging at term equivalent age and an assessment of verbal (Digit Span) and visuospatial (Corsi Blocks) working memory at 6 years corrected age. Compared to children born full term (N = 108), very preterm children were characterized by poorer verbal and visuospatial working memory performance. Very preterm children without cerebral abnormalities performed similarly to full-term children. Verbal impairments were largely confined to children with earlier moderate-severe cerebral abnormalities, while children with mild and moderate-severe abnormalities showed greater difficulties in visuospatial working memory. Findings suggest that very preterm children may be particularly vulnerable to visuospatial impairment. They also highlight the role of early neurological disturbance in the evolution of these difficulties.

The Role of Distinct Components of Visuo-spatial Working Memory in the Processing of Texts

Three experiments examined whether visuo-spatial working memory is involved in processing spatial descriptions and tested whether different processes within the visuo-spatial working memory are involved in processing different kinds of descriptions. Experiment 1 considered the performance of two groups with low and high visuo-spatial working memory abilities in memorising the description of a city. The high visuo-spatial working memory group had a better memory performance than the low visuo-spatial working memory group. In Experiment 2, the Brooks' (1967) task was adapted to investigate the selective interference of four different concurrent tasks (a verbal, a visual, a spatial-sequential, and a spatial-simultaneous task) on the recall of short abstract, visual and spatial texts. In Experiment 3, the same distinction was extended to longer and natural descriptions of different environments. Participants listened to three descriptions: a description that mainly stressed the visual properties of an environment, a description from a route perspective, and a description from a survey perspective. They also performed the concurrent visual and the two concurrent spatial tasks proposed in Experiment 2. Results of Experiments 2 and 3 demonstrated that tasks involving different cognitive resources (i.e. the verbal, visual, spatial-simultaneous, and the spatial-sequential tasks) had a differential interference with the free recall of different kinds of descriptions.