Effects of inhibiting of response on Tower of London performance

The purpose of this study was to determine if inhibiting responses improves performance on the Tower of London (TOL). The TOL has been assumed, though not experimentally proven, to be a measure of problem-solving ability. Problem solving involves inhibiting responses. Finding inhibition to be a factor in successfully completing TOL tasks would help to validate this tool and the research that utilizes it. Student volunteers were randomly assigned to two groups. Inhibition was induced in one of the groups by experimenter suggestion before each trial. The mean performance of the inhibited group was significantly higher, which suggests inhibiting responses increases TOL performance.     

Understanding planning ability measured by the Tower of London: an evaluation of its internal structure by latent variable modeling

The Tower of London (TOL) is a widely used instrument for assessing planning ability. Inhibition and (spatial) working memory are assumed to contribute to performance on the TOL, but findings about the relationship between these cognitive processes are often inconsistent. Moreover, the influence of specific properties of TOL problems on cognitive processes and difficulty level is often not taken into account. Furthermore, it may be expected that several planning strategies can be distinguished that cannot be extracted from the total score. In this study, a factor analysis and a latent class regression analysis were performed to address these issues. The results showed that 4 strategy groups that differed with respect to preplanning time could be distinguished. The effect of problem properties also differed for the 4 groups. Additional analyses showed that the groups differed on average planning performance but that there were no significant differences between inhibition and spatial working memory performance. Finally, it seemed that multiple factors influence performance on the TOL, the most important ones being the score measurements, the problem properties, and strategy use.     

The Tower of London Test: different scoring criteria for diagnosing Alzheimer's disease and mild cognitive impairment

The Tower of London (TOL) is used for evaluating planning skills, which is a component of the executive functions. Different versions and scoring criteria were developed for this task, and some of them present with different psychometrical properties. This study aimed to evaluate two specific scoring methods of the TOL in diagnosing Mild Cognitive Impairment and probable Alzheimer's disease. The TOL total scores from 60 patients of each diagnosis were compared with the performance of 60 healthy-aged controls using receiver operating characteristics analysis and multinomial logistic regression. Krikorian method better diagnosed Alzheimer's disease, while Portellas's was better at discriminating healthy controls from Mild Cognitive Impairment, but were not efficient at comparing this last group with Alzheimer's patients. Regression analysis indicates that in addition to screening tests, TOL improves the classification of the three groups. The results suggest the two scoring methods used for this task may be useful for different diagnostic purposes.     

Visuospatial over verbal demands in predicting Tower of London planning tasks

The role of verbal and visuospatial information processing in Tower of London (TOL) tasks was investigated. The first part of the investigation examined the verbal and visuospatial abilities and preferred cognitive style (visualizer vs. verbalizer) of 79 participants, in an inter-individual differences approach. Visuospatial abilities significantly predicted TOL performance, but the impact of cognitive style was negligible. The second part applied a dual-task manipulation of concurrent interference of TOL planning tasks on verbal and visuospatial memory, using the same participants. Concurrent processing of the TOL tasks diminished visuospatial memory performance considerably but had no effect on verbal memory, and there was no interaction between cognitive style and memory. These findings clearly underscore the role of visuospatial information processing in TOL tasks and indicate little bearing of verbal or visual cognitive style on TOL problem solving. These results have important implications for TOL and cognitive style in clinical application and cognitive neuroimaging research.     

A model point of view

This paper reports a study of planning processes in the five-disc Tower of London (TOL) task in 20 younger and 20 older adult participants. A concurrent direct “think-aloud” method was used to obtain data on planning processes prior to moving discs in the TOL. A check was made of the effects of verbalising by comparing performance data from the experimental groups with data from control groups who did not verbalise during planning or moving. Verbalising slowed down planning and moving but did not appear to distort the participants' approaches to the task. Older and younger participants did not differ in average moves taken to solve the tasks. However, older participants' planning was less complete and more error-prone than that of younger participants. The planning processes were characterised as showing a means-ends “goal selection” strategy. In this strategy participants (1) identify a single active goal disc at the start, (2) select moves and move sequences to enable the placing of the current goal disc in its target position, and (3) continue in this way until all discs are in their target positions. Age differences were found in the planning stage, during which there was no stimulus support and hence a substantial working memory load. During the move phase there was stimulus support and hence little loading of working memory. Age differences in moves required were not found in the move phase. As older participants tend to have depleted working memory capacity the present results suggest that working memory is heavily loaded in TOL planning but less so in the move phase of TOL.     

The Role of Memory in the Tower of London Task

The Tower of London (TOL) task is widely used as a neuropsychological test of planning. Relatively little is known of the cognitive components of the task, and in particular the role of memory in performance. The current studies on normal adults looked at the role of verbal and spatial working memory in the TOL. The effects of verbal and visuospatial dual-task manipulations on TOL performance were examined in an experiment with 36 participants. Both verbal and visuospatial executive secondary tasks caused poorer performance on the TOL; however, concurrent articulatory suppression enhanced performance. The results suggest that executive and spatial components are important in the task, and raise questions about the role of preplanning in the TOL.     

The role of memory in the Tower of London task

The Tower of London (TOL) task is widely used as a neuropsychological test of planning. Relatively little is known of the cognitive components of the task, and in particular the role of memory in performance. The current studies on normal adults looked at the role of verbal and spatial working memory in the TOL. The effects of verbal and visuospatial dual-task manipulations on TOL performance were examined in an experiment with 36 participants. Both verbal and visuospatial executive secondary tasks caused poorer performance on the TOL; however, concurrent articulatory suppression enhanced performance. The results suggest that executive and spatial components are important in the task, and raise questions about the role of preplanning in the TOL.     

Mental planning and the Tower of London task

The Tower of London (TOL) task has been used extensively as a test of planning ability in neuropsychological patients and normal populations. Participants are asked to preplan mentally a sequence of moves to match a start set of discs to a goal, and then to execute the moves one by one. The mental preplanning stage has been identified as critical to efficient performance. The current experiments examined whether manipulations of mental preplanning influence performance on the TOL. In Experiment 1, the effect of different planning instructions was examined. Those told to make full mental plans spent considerably longer in planning than participants given no specific planning instructions, yet there was no effect of instruction condition on the efficiency of executing plans. Experiment 2 investigated whether people were able to plan mentally, by looking at their ability to identify intermediate states of an optimum mental plan. Results indicated that most individuals could make accurate preplans up to two subgoals ahead, but not three. However, making an efficient preplan did not result in better subsequent execution of moves to solve the TOL trial. It is concluded that people can make effective mental plans for a limited number of moves. However, on the TOL task, mental preplanning does not offer benefits in terms of quicker performance, or more accurate solution. The nature of planning in the TOL task is therefore questioned.     

Prospective Memory and Pediatric Traumatic Brain Injury: Effects of Cognitive Demand

This study investigated the effects of pediatric traumatic brain injury (TBI) on prospective memory. Fourteen children and 14 adolescents with TBI were compared with 25 and 23 noninjured children and adolescents, respectively. Based on a prefrontal model, the cognitive demand on the ongoing component of a prospective-memory task was manipulated. Overall, those with TBI had poorer prospective-memory performance than their noninjured peers. Performance was worse in a high cognitive-demand condition than a low, and younger children performed worse than adolescents. Decreases in performance from the low- to high-demand conditions were not significantly different between the two children's groups but were between the two adolescents' groups. Furthermore, the age and injury effects were reflected in the performances on executive function tests: the Self-ordered Pointing Task (SOPT), and the Stroop Color Word Interference Test. The Tower of London (TOL), which did not produce age or injury effects, was nevertheless found to be an important predictor of performance on the high-demand task in those with TBI. Although previous research has demonstrated impaired prospective memory performance in children with TBI, this study attempted to explain why this might occur, specifically that the prefrontal regions might be implicated.     

Prospective memory and pediatric traumatic brain injury: effects of cognitive demand.

This study investigated the effects of pediatric traumatic brain injury (TBI) on prospective memory. Fourteen children and 14 adolescents with TBI were compared with 25 and 23 noninjured children and adolescents, respectively. Based on a prefrontal model, the cognitive demand on the ongoing component of a prospective-memory task was manipulated. Overall, those with TBI had poorer prospective-memory performance than their noninjured peers. Performance was worse in a high cognitive-demand condition than a low, and younger children performed worse than adolescents. Decreases in performance from the low- to high-demand conditions were not significantly different between the two children's groups but were between the two adolescents' groups. Furthermore, the age and injury effects were reflected in the performances on executive function tests: the Self-ordered Pointing Task (SOPT), and the Stroop Color Word Interference Test. The Tower of London (TOL), which did not produce age or injury effects, was nevertheless found to be an important predictor of performance on the high-demand task in those with TBI. Although previous research has demonstrated impaired prospective memory performance in children with TBI, this study attempted to explain why this might occur, specifically that the prefrontal regions might be implicated.     

Tower of London: What Level of Planning Does it Measure?

We examined which of two levels of planning, namely action and operations planning, are involved in Tower of London (TOL). One hundred nine university students (79 females; mean age = 20.81 years) from China were assessed on measures of action planning (Crack the Code), operations planning (Planned Connections, Planned Codes, Matching Numbers), and on TOL. The results of factor analysis showed first that TOL, scored as total number of correct responses, had a split loading on action and operations planning. TOL, scored as first move time, loaded on the same action planning factor represented by Crack the Code first move time. These findings suggest that different TOL scores may capture different levels of planning. The implications of these findings especially for clinical diagnosis and rehabilitation are briefly discussed.     

Deconstructing the tower: Parameters and predictors of problem difficulty on the Tower of London task

The Tower of London (TOL) task has been widely used in both clinical and research realms. In the current study, 104 healthy participants attempted all possible moderate- to high-difficulty TOL problems in order to determine: (1) optimal measures of problem solving performance, (2) problem characteristics, other than the minimum moves necessary to solve the problem, that determine participants’ difficulty in solving problems successfully, quickly, and efficiently, and (3) effects of increased task experience on which problem characteristics determine problem difficulty. A factor analysis of six performance measures found that, regardless of task experience, problem difficulty could be captured well either by a single factor corresponding to general quality of solution or possibly by three subordinate factors corresponding to solution efficiency, solution speed, and initial planning speed. Regression analyses predicting these performance factors revealed that in addition to a problem’s minimum moves three problem parameters were critical in determining the problem difficulty: goal position hierarchy, start position hierarchy, and number of solution paths available. The relative contributions of each of the characteristics strongly depended on which performance factor defined performance. We conclude that TOL problem performance is multifaceted, and that classifying problem difficulty using only the minimum moves necessary to solve the problem is inadequate.     

Mental fatigue and the control of cognitive processes: effects on perseveration and planning

We tested whether behavioural manifestations of mental fatigue may be linked to compromised executive control, which refers to the ability to regulate perceptual and motor processes for goal-directed behaviour. In complex tasks, compromised executive control may become manifest as decreased flexibility and sub-optimal planning. In the study we use the Wisconsin Card Sorting Test (WCST) and the Tower of London (TOL), which respectively measure flexibility (e.g., perseverative errors) and planning. A simple memory task was used as a control measure. Fatigue was induced through working for 2 h on cognitively demanding tasks. The results showed that compared to a non-fatigued group, fatigued participants displayed more perseveration on the WCST and showed prolonged planning time on the TOL. Fatigue did not affect performance on the simple memory task. These findings indicate compromised executive control under fatigue, which may explain the typical errors and sub-optimal performance that are often found in fatigued people.     

Associations of transcranial doppler velocity,age, and gender with cognitive function in children with sickle cell anemia in Nigeria

Children with sickle cell anemia (SCA) have elevated cerebral blood velocity relative to healthy peers. The primary aim of this study was to evaluate the association between cerebral blood velocity, measured by transcranial Doppler (TCD) ultrasound, age, and gender with cognitive function in children with SCA in Nigeria. Eighty-three children (M_age = 9.10, SD = 1.90 years; 55% female) with SCA in Nigeria completed cognitive assessments and a TCD ultrasound. The association between TCD velocity and measures of perceptual reasoning (Raven’s Progressive Matrices), working memory (WISC-IV Digit Span), and executive planning (Tower of London, TOL) were assessed. Results showed that elevated TCD velocity significantly predicted lower scores on TOL Time Violations and Total Problem-Solving Time when controlling for BMI, hemoglobin level, and parent education, suggesting that TCD velocity is related to the efficiency of executive function. Further, age was negatively related to children’s performance on the Ravens Matrices and TOL Total Correct, and boys showed greater deficits on the TOL Total Correct relative to girls. Moderation analyses for gender showed that there was a conditional negative association between TCD velocity and Digit Span for boys, but not for girls. Findings suggest that children with SCA in Nigeria with elevated TCD velocity are at risk for deficits in efficiency of executive planning, and boys with elevated TCD velocity are particularly at increased risk for deficits in auditory working memory. Implications of this study are important for interventions to reduce cerebral blood velocity and the use of TCD in this population.     

Working memory, inhibition, and fluid intelligence as predictors of performance on Tower of Hanoi and London tasks

The contributions of working memory, inhibition, and fluid intelligence to performance on the Tower of Hanoi (TOH) and Tower of London (TOL) were examined in 85 undergraduate participants. All three factors accounted for significant variance on the TOH, but only fluid intelligence accounted for significant variance on the TOL. When the contribution of fluid intelligence was accounted for, working memory and inhibition continued to account for significant variance on the TOH. These findings support argument that fluid intelligence contributes to executive functioning, but also show that the executive processes elicited by tasks vary according to task structure.     

Visuo-spatial and verbal working memory in the five-disc Tower of London task: An individual differences approach

This paper reports a study of the roles of visuo-spatial and verbal working memory capacities in solving a planning task—the five-disc Tower of London (TOL) task. An individual differences approach was taken. Sixty adult participants were tested on 20 TOL tasks of varying difficulty. Total moves over the 20 TOL tasks was taken as a measure of performance. Participants were also assessed on measures of fluid intelligence (Raven's matrices), verbal short-term storage (Digit span), verbal working memory span (Silly Sentence span), visuo-spatial short-term storage (Visual Pattern span and Corsi Block span), visuo-spatial working memory (Corsi Distance Estimation), visuo-spatial processing speed (Manikin test), and verbal speed (Rehearsal speed). Exploratory factor analysis using an oblique rotation method revealed three factors which were interpreted as (1) a visuo-spatial working memory factor, (2) an age-speed factor, and (3) a verbal working memory factor. The visuo-spatial and verbal factors were only moderately correlated. Performance on the TOL task loaded on the visuo-spatial factor but did not load on the other factors. It is concluded that the predominant goal-selection strategy adopted in solving the TOL relies on visuo-spatial working memory capacity and particularly involves the active “inner scribe” spatial rehearsal mechanism. These correlational analyses confirm and extend results previously obtained by use of dual task methods, (Phillips, Wynn, Gilhooly, Della Sala, & Logie, 1999).     

Age,working memory,and the Tower of London task

The current study explores the role of three components of working memory in age differences in an executive task, the Tower of London (TOL). The TOL task is sensitive to frontal lobe damage, and is widely used to measure planning ability. Dual tasks were used to test the involvement of the phonological loop (articulatory suppression), visuospatial buffer (pattern tapping), and central executive (random generation) in age effects on the TOL. Older adults showed greater reliance than young on domain-specific verbal and spatial memory components in performing the TOL. In terms of executive function, qualitatively different interference patterns were seen in young and old participants. However, the validity of using random generation tasks to assess executive function in older populations can be questioned. For older participants, performing the TOL loads all components of working memory, whereas for the younger participants the TOL more specifically loads executive functioning.     

A Latent Profile Analysis of the Criterion-related Validity of a Divergent Thinking Test

The criterion-related validity of divergent thinking (DT) tests has been questioned because of relatively low correlations between DT test scores and creative performance. A possible inhibiting factor in previous correlations—heterogeneity of the sample—has been ignored. If groups with different DT profiles are involved in this line of research, low correlations would not necessarily be indicative of actual relationships, and criterion-related validity would appear to be lower than it is. Thus, this study identified groups with their own unique DT profiles and examined their creative performance. To this end, elementary children’s (N = 325) responses in 3 DT tasks were analyzed using latent profile analysis. Results suggested 3 groups with unique DT profiles: One group scored moderate on fluency and low on originality; another group scored moderate on fluency and high on originality; the third group scored uniformly low across fluency, originality, and flexibility. Surprisingly, only the low-originality group excelled in creative achievement, but the hypothesis of this investigation was supported by the fact that only the high-originality group significantly excelled in ideation. These results confirm that low correlations between DT indices and creative performance do not necessarily indicate a lack of the criterion-related validity of DT tests. Differences between the creative achievement and the ideation criterion measures are detailed, and idiosyncratic properties in DT profiles and their corresponding creative strengths are discussed as educational implications.     

Counterintuitive and alternative moves choice in the Water Jug task

MOVE problems, like the Tower of London (TOL) or the Water Jug (WJ) task, are planning tasks that appear structurally similar and are assumed to involve similar cognitive processes. Carder et al. [Carder, H.P., Handley, S.J., & Perfect, T.J. ( 2004). Deconstructing the Tower of London: Alternative moves and conflict resolution as predictors of task performance. The Quarterly Journal of Experimental Psychology 57a, 8, 1459-1483] showed that one predictor of TOL performance was the number of alternative move choices there were at a given point in the solution. In two experiments an individual move experienced on the WJ task was manipulated (perceptually consistent/counterintuitive) along with the number of alternative moves there were to choose between. A verification paradigm was employed in which participants made speeded judgements about the correctness of a move. Results showed performance was consistent with the application of a perceptual strategy accompanied by a process involving the evaluation of non-redundant alternative moves. These are discussed in the context of recent research that has examined the impact of executive dysfunction on Water Jug performance [Colvin, M.K., Dunbar, K., & Grafman, J. (2001). The effects of frontal lobe lesions on goal achievement in the Water Jug task. Journal of Cognitive Neuroscience, 13, 1129-1147].     

Brief report: Response inhibition and processing speed in children with motor difficulties and developmental coordination disorder

A previous study reported that children with poor motor skills, classified as having motor difficulties (MD) or Developmental Coordination Disorder (DCD), produced more errors in a motor response inhibition task compared to typically developing (TD) children but did not differ in verbal inhibition errors. The present study investigated whether these groups differed in the length of time they took to respond in order to achieve these levels of accuracy, and whether any differences in response speed could be explained by generally slow information processing in children with poor motor skills. Timing data from the Verbal Inhibition Motor Inhibition test were analyzed to identify differences in performance between the groups on verbal and motor inhibition, as well as on processing speed measures from standardized batteries. Although children with MD and DCD produced more errors in the motor inhibition task than TD children, the current analyses found that they did not take longer to complete the task. Children with DCD were slower at inhibiting verbal responses than TD children, while the MD group seemed to perform at an intermediate level between the other groups in terms of verbal inhibition speed. Slow processing speed did not account for these group differences. Results extended previous research into response inhibition in children with poor motor skills by explicitly comparing motor and verbal responses, and suggesting that slow performance, even when accurate, may be attributable to an inefficient way of inhibiting responses, rather than slow information processing speed per se.