Evidence against the relative invariance of timing in handwriting

Gentner (1987) has called into question the role of timing information in a number of motor behaviours. The status of an invariant relative timing model for handwriting, however, is still unclear, due to lack of previous studies that have applied appropriate tests to a suitable database.

This study employs a direct application of the tests proposed by Gentner (1987) to handwriting samples collected from adult subjects, to ascertain whether an invariant temporal pattern was retained across changes in size and speed of writing.

In line with Gentner's (1987) study of typing, the findings are strongly against the invariant relative timing model and bring into question motor program models that posit timing as an independent parameter.     

Dyslexic children fail to comply with the rhythmic constraints of handwriting

In this study, we sought to demonstrate that deficits in a specific motor activity, handwriting, are associated to Developmental Dyslexia. The linguistic and writing performance of children with Developmental Dyslexia, with and without handwriting problems (dysgraphia), were compared to that of children with Typical Development. The quantitative kinematic variables of handwriting were collected by means of a digitizing tablet. The results showed that all children with Developmental Dyslexia wrote more slowly than those with Typical Development. Contrary to typically developing children, they also varied more in the time taken to write the individual letters of a word and failed to comply with the principles of isochrony and homothety. Moreover, a series of correlations was found among reading, language measures and writing measures suggesting that the two abilities may be linked. We propose that the link between handwriting and reading/language deficits is mediated by rhythm, as both reading (which is grounded on language) and handwriting are ruled by principles of rhythmic organization.     

A quantitative evaluation of the AVITEWRITE model of handwriting learning

Much sensory-motor behavior develops through imitation, as during the learning of handwriting by children. Such complex sequential acts are broken down into distinct motor control synergies, or muscle groups, whose activities overlap in time to generate continuous, curved movements that obey an inverse relation between curvature and speed. The adaptive vector integration to endpoint handwriting (AVITEWRITE) model of Grossberg and Paine (2000) [A neural model of corticocerebellar interactions during attentive imitation and predictive learning of sequential handwriting movements. Neural Networks, 13, 999-1046] addressed how such complex movements may be learned through attentive imitation. The model suggested how parietal and motor cortical mechanisms, such as difference vector encoding, interact with adaptively-timed, predictive cerebellar learning during movement imitation and predictive performance. Key psychophysical and neural data about learning to make curved movements were simulated, including a decrease in writing time as learning progresses; generation of unimodal, bell-shaped velocity profiles for each movement synergy; size scaling with isochrony, and speed scaling with preservation of the letter shape and the shapes of the velocity profiles; an inverse relation between curvature and tangential velocity; and a two-thirds power law relation between angular velocity and curvature. However, the model learned from letter trajectories of only one subject, and only qualitative kinematic comparisons were made with previously published human data. The present work describes a quantitative test of AVITEWRITE through direct comparison of a corpus of human handwriting data with the model's performance when it learns by tracing the human trajectories. The results show that model performance was variable across the subjects, with an average correlation between the model and human data of 0.89+/-0.10. The present data from simulations using the AVITEWRITE model highlight some of its strengths while focusing attention on areas, such as novel shape learning in children, where all models of handwriting and the learning of other complex sensory-motor skills would benefit from further research.     

Attention and movement execution during handwriting

Two studies were performed in order to test the hypothesis that movement execution during handwriting in skilled writers is independent of attention. Study I examined the relationship between attentional functioning and kinematic aspects of handwriting movements in 24 adult participants. A digitizing tablet was used for the assessment of handwriting movements. Participants were asked to perform a simple writing task and various components of their attention were assessed. Correlation analysis indicated no significant relationship between attention functions and both kinematic aspects of handwriting movements and quality of handwriting. In Study II, 20 participants underwent total sleep deprivation (TSD) for 24h. While attention, as assessed with alertness and vigilance tasks, deteriorated during TSD, the execution of handwriting movements, as assessed with a digitizing tablet, improved markedly. The quality of handwriting was not affected by TSD. These findings may suggest an independence between attention and movement generation during handwriting.     

Effects of methylphenidate on kinematic aspects of handwriting in hyperactive boys

Poor handwriting in hyperactive children often contributes to academic failure. Beneficial effects of methylphenidate on the quality of handwriting have been shown. Using a digitizing tablet, the handwriting of 21 hyperactive boys was examined both during methylphenidate treatment and following withdrawal of the drug. Half of the hyperactive boys were tested first on methylphenidate and then following withdrawal of the drug and the remaining hyperactive boys were examined in the reverse order. Twenty-one control boys underwent the same examination. Velocity and acceleration of handwriting movements were measured. Furthermore, every writing specimen was independently rated by four examiners regarding the quality of handwriting. Following withdrawal of the drug, the quality of handwriting specimens of hyperactive boys was poorer than during treatment with methylphenidate. Statistical comparison of writing movements of hyperactive boys on and off methylphenidate revealed that the medication resulted in a deterioration in handwriting fluency. The results showed that following withdrawal of medication, hyperactive children did not differ from control boys in handwriting movements. The improvement in hyperactive behavior through methylphenidate was associated with increased legibility and greater accuracy of handwriting. The intention to write neatly may interfere with the fluent writing process.     

The effect of conscious control on handwriting in children with attention deficit hyperactivity disorder

Two experiments were performed regarding the effect of conscious control on handwriting fluency in healthy adults and ADHD children. First, 26 healthy students were asked to write a sentence under different conditions. The results indicate that automated handwriting movements are independent from visual feedback. Second, the writing performance of 12 children with ADHD was examined on their usual medication with methylphenidate and under placebo. In comparison to placebo, medication with methylphenidate resulted in a reduced fluency of handwriting. Automated handwriting movements could be elicited in children with ADHD on medication. The results suggest that both visual and mental control of handwriting movements affect the automation of handwriting movements. Furthermore, a simple training procedure was designed and performed in a case study of a boy with ADHD.     

Visual perceptual and handwriting skills in children with Developmental Coordination Disorder

ObjectiveChildren with Developmental Coordination Disorder demonstrate a lack of automaticity in handwriting as measured by pauses during writing. Deficits in visual perception have been proposed in the literature as underlying mechanisms of handwriting difficulties in children with DCD. The aim of this study was to examine whether correlations exist between measures of visual perception and visual motor integration with measures of the handwriting product and process in children with DCD.MethodThe performance of twenty-eight 8–14 year-old children who met the DSM-5 criteria for DCD was compared with 28 typically developing (TD) age and gender-matched controls. The children completed the Developmental Test of Visual Motor Integration (VMI) and the Test of Visual Perceptual Skills (TVPS). Group comparisons were made, correlations were conducted between the visual perceptual measures and handwriting measures and the sensitivity and specificity examined.ResultsThe DCD group performed below the TD group on the VMI and TVPS. There were no significant correlations between the VMI or TVPS and any of the handwriting measures in the DCD group. In addition, both tests demonstrated low sensitivity.ConclusionClinicians should execute caution in using visual perceptual measures to inform them about handwriting skill in children with DCD.     

Dynamic time warping: a new method in the study of poor handwriting

Poor handwriting is a diagnostic criterion for developmental coordination disorder. Typical of poor handwriting is its low overall quality and the high variability of the spatial characteristics of the letters, usually assessed with a subjective handwriting scale. Recently, Dynamic Time Warping (DTW), a technique originally developed for speech recognition, was introduced for pattern recognition in handwriting. The present study evaluates its application to analyze poor handwriting. Forty children attending Dutch mainstream primary schools were recruited and based on their scores on the Concise Evaluation Scale for Children's Handwriting (Dutch abbreviation: BHK), 20 good and 20 poor writers (of whom 13 were scheduled for handwriting intervention) were identified. The groups were matched for age (7-9 years), school grade (grades 2 and 3) and handedness. The children subsequently wrote sequences of the letter "a" on a graphics tablet in three conditions (normal, fast, and accurate). Classical kinematics were obtained and for each individual letter DTW was used to calculate the distance from the mean shape. The DTW data revealed much higher variability in the letter forms of the poor writers that was independent of the kinematic results of larger trajectories, faster movements, and higher pen pressure. The current results suggest that DTW is a valid and objective technique for letter-form analysis in handwriting and may hence be useful to evaluate the rehabilitation treatments of children suffering from poor handwriting. In education research it may be exploited to explore how children (should) learn to write.     

Timing and the Control of Rhythmic Upper-Limb Movements

Accurate timing of limb displacement is crucial for effective motor control. The authors examined the effects of movement velocity, duration, direction, added mass, and auditory cueing on timing, spatial, and trajectory variability of single- and multijoint rhythmic movements. During single-joint movements, increased velocity decreased timing and spatial variability, whereas increased movement duration increased timing variability but decreased spatial variability. For multijoint movements, regardless of condition, increasing velocity decreased joint timing, spatial, and trajectory variability, but all hand variabilities were unaffected by velocity, duration, load, or direction. Timing, spatial, and trajectory variability was greater at the shoulder compared with the elbow and minimal at the hand, supporting the notion that reaching movements are planned in hand space as opposed to joint space.     

The effect of caffeine on handwriting movements in skilled writers

In laboratory tasks, caffeine has been shown to improve psychomotor performance. The aim of the present experiment was to assess the effects of caffeine on a skilled everyday life task in habitual caffeine consumers. The assessment of handwriting movements of 20 adults was performed following the administration of 0mg/kg (placebo), 1.5mg/kg, 3.0mg/kg or 4.5mg/kg of caffeine. A digitising tablet was used for the assessment of fine motor movements. Participants were asked to perform a simple writing task. Kinematic analysis of handwriting movements showed that, in comparison to placebo administration, high doses of caffeine (i.e., 4.5mg/kg) can produce improvements in handwriting as indicated by more fluent handwriting movements as well as an increase in maximum velocity and maximum positive and negative accelerations. The results suggest that higher doses of caffeine can enhance psychomotor performance.     

Lifts and stops in proficient and dysgraphic handwriting

In this study, the handwriting performances of dysgraphic children were compared to those of proficient children and adults. The task consisted in writing a single word at normal and fast speeds. A distinction was made between two kinds of pauses, which are often confounded: pen lifts, when the pen is above the paper, and pen stops, when it is immobile on the paper. The number and duration of lifts and stops were analyzed, together with the mean velocity. No difference in the number of lifts was observed between the three groups of writers, but the lift durations were shorter for adults. While dysgraphic children were able to write as fast as proficient children, their stops were more numerous and longer than those of proficient children who, themselves, made more stops than adults. A distinction was made between short, normal, and long, abnormal, stops. The results of this study suggest that pen stops are more appropriate than pen lifts in differentiating the handwriting fluency of dysgraphic and proficient children.     

The effect of perceptual-motor continuity compatibility on the temporal control of continuous and discontinuous self-paced rhythmic movements

One of the questions yet to be fully understood is to what extent the properties of the sensory and the movement information interact to facilitate sensorimotor integration. In this study, we examined the relative contribution of the continuity compatibility between motor goals and their sensory outcomes in timing variability. The variability of inter-response intervals was measured in a synchronization-continuation paradigm. Participants performed two repetitive movement tasks whereby they drew circles either using continuous or discontinuous self-paced movements while receiving discrete or continuous auditory feedback. The results demonstrated that the effect of perceptual-motor continuity compatibility may be limited in self-paced auditory-motor synchronization as timing variability was not significantly influenced by the continuity of the feedback or the continuity compatibility between feedback and the movement produced. In addition, results suggested that the presence of salient perceptual events marking the completion of the time intervals elicited a common timing process in both continuous and discontinuous circle drawing, regardless of the continuity of the auditory feedback. These findings open a new line of investigation into the role of the discriminability and reliability of the event-based information in determining the nature of the timing mechanisms engaged in continuous and discontinuous self-paced rhythmic movements.     

Analysis of timing variability in human movements by aligning parameter curves in time

The analysis of timing in human movements requires a reference with which timing can be quantified. In reactive movements this reference is given by the stimulus. However, many movements do not respond to such an external event. In throwing, for instance, the hand opening for release has to be timed to an acceleration of the throwing arm. A common approach to analyzing release-timing variability is to choose a landmark in the movement that is supposed to have a fixed temporal relation to the release. Such distinct landmarks, however, are not always well definable. Therefore, the present article describes an alternative approach analyzing timing variability on the basis of the alignment of different trials relative to their kinematic shape, by shifting the trials in the time domain. The basic assumption behind this approach is that single throwing movements are one instance of an acquired movement template, and thus show a considerable similarity. In contrast, the location of the temporal moment of release varies from trial to trial, generating imprecision regarding the release timing. In trials synchronized with respect to the release, this variability can be assessed by shifting the kinematic profiles of the throwing movements in time such that they superimpose as closely as possible. As a result, the corresponding time shifts for all trials represent a measure of the release time deviations across trials, and the standard deviation of these deviations represents the timing variability. Aside from timing analyses in such movements as throwing, the approach can be applied to very different tasks with timing demands—for example, to neurophysiological signals.     

Studying the variability of handwriting patterns using the Kinematic Theory

The variability observed in handwriting patterns is analyzed from the perspective of integrating the resulting motor control knowledge in the design of more powerful handwriting recognizers in personal digital assistants (PDAs) and smartphones. Using the highest representational level of the Kinematic Theory of Rapid Human Movement, the Sigma-Lognormal model, this article reports basic theoretical and practical results that could be taken into account in the design of such systems. The main movement variability introduced by the neuromuscular system (NMS) and induced through the scheduling of motor tasks by the central nervous system (CNS) is divided into global and local fluctuations. From a fiducial action plan decoded by this model, a wide range of handwriting distortions are artificially generated by acting on the Sigma-Lognormal parameters. The resulting patterns are studied to understand scale changes and rotational deformations, the two basic features that a recognizer has to take into account. An experiment based on the writing of the same word by six writers is also reported. The results, obtained by an ANOVA analysis, corroborate the predictions and support the relevance of the Kinematic Theory for the analysis and synthesis of handwriting disruptions. These findings consolidate the results of previous studies on single strokes using the Sigma-Lognormal model. Overall, this report provides new insights into our understanding of motor control, as well as into practical cues for the development of huge databases of letters and words to train and test on-line handwriting classifiers and recognizers.     

Eye movements during the handwriting of words: Individually and within sentences

Handwriting, a complex motor process involves the coordination of both the upper limb and visual system. The gaze behavior that occurs during the handwriting process is an area that has been little studied. This study investigated the eye-movements of adults during writing and reading tasks. Eye and handwriting movements were recorded for six different words over three different tasks. The results compared reading and handwriting the same words, a between condition comparison and a comparison between the two handwriting tasks. Compared to reading, participants produced more fixations during handwriting tasks and the average fixation durations were longer. When reading fixations were found to be mostly around the center of word, whereas fixations when writing appear to be made for each letter in a written word and were located around the base of letters and flowed in a left to right direction. Between the two writing tasks more fixations were made when words were written individually compared to within sentences, yet fixation durations were no different. Correlation of the number of fixations made to kinematic variables revealed that horizontal size and road length held a strong correlation with the number of fixations made by participants.     

Ductus: A software package for the study of handwriting production

Ductus is a software tool designed to analyze and aid understanding of the processes underlying handwriting production. Ductus is a digitizer-based device that provides online information on the handwriting process. It consists of two distinct modules that operate independently. The first module concerns stimulus presentation. It is particularly suited to experiments with children and patients presenting handwriting pathologies. The second module is devoted to data analysis. Apart from the geometrical aspects of handwriting, such as trajectory formation, Ductus provides a wide range of kinematic information, such as velocity, duration, fluency, and pauses, linked to the mastery of the movement itself. Ductus is available free from the authors. It works on a Windows platform with Wacom digitizers.     

Tier 1 and Tier 2 early intervention for handwriting and composing

Three studies evaluated Tier 1 early intervention for handwriting at a critical period for literacy development in first grade and one study evaluated Tier 2 early intervention in the critical period between third and fourth grades for composing on high stakes tests. The results contribute to knowledge of research-supported handwriting and composing instruction that informs practice as school psychologists are empowered to embrace the role of intervention specialist. The first study found that neurodevelopmental training (orthographic-free motor activities and motor-free orthographic activities) led to improved accuracy and legibility of letter formation, but that direct handwriting instruction with visual cues and verbal mediation led to improved automatic handwriting (rate of writing legible letters) and transfer to improved word reading. The second study found that neither motor training nor orthographic training alone added value to direct instruction in automatic letter writing and composing practice in developing handwriting skills, which transferred to improved word reading; but the added motor training did improve performance on a grapho-motor planning task for sequential finger movements that is relevant to composing. A related analysis showed that direct instruction with visual cues and memory delays may reduce reversals. A third study found that adding handwriting to reading instruction improved handwriting but did not add value to reading outcomes for at risk readers; reading instruction alone was beneficial for word reading, decoding, and comprehension. The fourth study showed that comprehensive, explicit instruction in the processes of composition led to more significant improvement, based on group and individual data, than did the regular fourth grade program, on high stakes writing assessment.     

Automatic segmentation as a tool for examining the handwriting process of children with dysgraphic and proficient handwriting

The purpose of this study was to use an x-y digitizer to collect handwriting samples typical of those written by the child in his or her natural environment, to analyze these samples with novel segmentation algorithms, and to present them visually in ways that illuminate spatial and temporal dynamic features amongst children with dysgraphic and proficient handwriting. While using the POET software (Penmanship Objective Evaluation Tool), a paragraph was copied onto paper affixed to an x-y digitizer by third-grade students, 14 with proficient and 14 with poor handwriting. A segmentation algorithm was developed to automatically isolate writing segments. Results yielded significant differences between the groups in various measures, including the number of the raw segments (i.e., the number of segments before combined with letters), the number of reverse segments (i.e., when the participant returned to correct or complete a previously written segment), the number of letters per minute, and the mean "In-Air" time between letters. Variability in both the spatial and temporal domains of instances of the same letter throughout the text was greater among the dysgraphic handwriters in comparison to the variability among the proficient. These results demonstrated the potential of using automated analytic techniques and visual display to achieve a more comprehensive understanding of handwriting difficulties.     

Cognitive processes in writing during pause and execution periods

The present study investigated how writing processes are activated during pause and execution periods. In two experiments, handwriting demands were manipulated by asking participants to compose with their familiar handwriting or with a high-demanding cursive uppercase calligraphy. Experiment 1 investigated narrative writing, a task with low planning demands. Experiment 2 addressed essay writing, a task with stronger planning demands. Occurrences of processes and their cognitive effort were analysed by asking participants to respond to random auditory probes and then to report their ongoing mental activity according to learned categories referring to the planning, translating, and revising writing processes. All together, the findings indicate that demands on planning did not affect how writing processes were activated during pauses and execution periods but automaticity of handwriting did. When handwriting was effortless, translating was mostly activated in parallel with motor execution, whereas revising and planning were mainly activated during pauses. However, none of the writing processes could be characterised as being typical of pauses, since translating was activated to a similar extent as the other two processes. By contrast, when handwriting was effortful, participants shifted to a more sequential functioning and activated translating mainly during pauses.