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Difficulties in handwriting, such as dysgraphia, impact several aspects of a child’s everyday life. Current methodologies for the detection of such difficulties in children have the following three main weaknesses: (1) they are prone to subjective evaluation; (2) they can be administered only when handwriting is mastered, thus delaying the diagnosis and the possible adoption of countermeasures; and (3) they are not always easily accessible to the entire community.
This work aims at developing a solution able to: (1) quantitatively measure handwriting features whose alteration is typically seen in children with dysgraphia; (2) enable their study in a preliteracy population; and (3) leverage a standard consumer technology to increase the accessibility of both early screening and longitudinal monitoring of handwriting difficulties.
We designed and developed a novel tablet-based app
App testing in 15 primary school children confirmed that the three laws hold on the tablet surface when both writing words and drawing symbols. We found significant speed modulation according to size (
The designed app represents a promising solution for the screening of handwriting difficulties, since it allows (1) anticipation of the detection of alteration of handwriting principles at a preliteracy age and (2) provision of broader access to the monitoring of handwriting principles. Such a solution potentially enables the selective strengthening of lacking abilities before they exacerbate and affect the child’s whole life.
Dysgraphia is a learning disability that involves unsatisfactory handwriting production, given age, normal intelligence, and absence of neurological, perceptual, or motor problems [
The exact epidemiology of dysgraphia is still under debate, resulting in differences in the diagnostic criteria adopted by different schools of thought [
The limitations of the diagnostic procedure contribute to uncertainty in the estimation of the actual incidence of the phenomenon. Indeed, the reported prevalence of handwriting problems ranges between 5% and 27% [
Against this background, there is an urgent need for innovative solutions to support the screening for dysgraphia. An effective solution must meet the following requirements: (1) quantitatively reveal potential alterations in writing production; (2) detect potential weaknesses at an early stage, thus enabling early intervention; and (3) be easily accessible to the user in order to reduce delayed diagnoses and allow longitudinal monitoring.
To meet the first requirement, understanding in which way dysgraphia alters the principles of handwriting is fundamental to quantify such alterations. It is known that handwriting problems are often linked to a lacking sense of rhythm [
Experts stress the concept that pupils with dysgraphia tend to write every single letter faster than typically developing peers, with greater pauses and poorer accuracy [
To meet the second requirement, uncovering the laws underlying handwriting in drawing is crucial. This would allow the detection of potential difficulties before the acquisition or at least before the complete maturation of the writing gesture. Previous studies on isochrony [
Finally, to meet the third requirement, leveraging standard consumer technology is key to allowing easy access to the screening process, as reported in other fields [
Given the highlighted needs, we devised and developed
The hardware chosen for the experiment was Samsung Galaxy Tab A with an S-Pen (
Experimental setup. A kindergartner is executing one of the exercises on the tablet with an S-Pen.
The app was developed in Unity 2018.3.2f1 following the principles of theory-driven evidence-based serious games for health [
The app
App interface. A: copy game; B: tunnel game.
The tunnel game was aimed at testing the speed-accuracy tradeoff for both words and symbols. Our purpose was to detect the adaptability to different task requirements (ie, accuracy). According to the steering law, accuracy is defined by the index of difficulty (ID) as follows:
ID = A / W (
where W is the width between the borders of the path and A is the amplitude of the gesture (ie, perimeter for symbols and the path length for words, both measured in the center of the path). We combined A and W to obtain five different IDs for words and five for symbols, following clinicians’ guidelines (
Data collection was performed on children attending the third grade of a primary school and the last year of a kindergarten in the province of Como, Italy. Target ages were selected as handwriting is mastered in third grade [
A minimum sample size of 10 children per group was computed on the basis of previous experiments in the field of the speed-accuracy tradeoff [
We collected data at the end of the school year. Acquisition took place in a quiet room with the child comfortably seated. The complete protocol (
In the copy game, the instructions were to copy the word/symbol shown in the upper part of the screen, in the indicated modality (
The experimental procedure was approved by the Ethics Committee of Politecnico di Milano (n.10/2019). Written consent was received from school deans, parents, and primary school children.
Study protocol. A: copy game; B: tunnel game.
Data analysis was performed in Matlab R2018b (MathWorks) and R 3.3.3 (R Development Core Team). Significance was set at .05. Given the small sample size, nonparametric statistics were selected for all tests.
First, instruction compliance was tested using a Wilcoxon matched paired test comparing the trajectory length between the
To test isochrony, separately for words and symbols, we considered between-condition differences in the average execution speed. To be compliant with the isochrony principle, we expected the
We considered speed, rather than time, to normalize the execution time for the size, as it was self-selected. For both words and symbols, we discarded the first and last 5% of the trajectory to avoid border effects. Thereafter, we computed speed as the ratio between the discrete difference between adjacent coordinates and the corresponding timestamps. We filtered the result with a 10-Hz low-pass filter, and we averaged the speed over the entire path to obtain a single value per execution. To test the effect of the modality on speed, we used Friedman and Bonferroni
To understand if the primary school and kindergarten groups approached the exercise differently, we performed, separately for each symbol, a Mann-Whitney
To test for homothety on both word and symbol sequences, we computed the percentage of time (
To study the speed-accuracy tradeoff during handwriting, the steering law was adopted. The steering law predicts a linear relationship between movement time (MT) and ID as follows:
MT = a + b ID (
To compute MT in the word “ele,” we considered the timestamp difference between the first “
To compute MT in symbols, we considered the central part of the execution as follows: for the circle, we discarded the first and last semicircles, leaving a complete central circle; for the square, we discarded the first two and the last two sides, leaving a complete central square. We discarded trials where more than 40% of the path was outside the borders [
Speed-accuracy tradeoff exercise. The transparent background represents the app interface.
Separately for the word and the two symbols, we calculated the
IP = 1 / b (
The IP is an index of adaptation to a task’s accuracy requirements [
We enrolled 15 right-handed primary school children (7 males and 8 females; mean age 8.8 years, SD 0.3) and 19 kindergartners (9 males and 10 females; 2 left handed; mean age 5.9 years, SD 0.4).
Test results are reported in
Isochrony. A: word, primary school; B: symbols, primary school; C: symbols, kindergarten. X-axis: execution modality; Y-axis: mean speed as box-and-whiskers plots. The red horizontal line is the median, the notch is its 95% CI, and the box is the IQR. Asterisks for between-condition differences involving the spontaneous modality are not reported for clarity purposes.*
Homothety. A and B: primary school; C: kindergarten. A: word; B and C: symbols. Each subplot represents one element of the sequence of letters or symbols. X-axis: execution modality; Y-axis: fraction time, in normalized unit (1 represents the total execution time) as box-and-whiskers plots. The red horizontal line is the median, the notch is its 95% CI, and the boxes represent the IQR. *
Speed-accuracy tradeoff. A: global movement time (ie, the median movement time computed across all indexes of difficulty). B: root mean square error (RMSE) (ie, the goodness of fit of the steering law). C: index of performance (ie, the inverse of the regression line slope). Data are divided by symbol/word and age group. *
Concerning the copy game, instruction compliance was confirmed by all subjects in all the tests. Indeed, the trajectory in the
The speed execution of the word “mele” (
A significant effect of the modality was also found for symbol speed execution in primary school children (
The copy game (
When investigating possible mean speed differences in the
When analyzing the fraction time of letters in primary school children (
As for the fraction time in the sequence of symbols (
As for the sequence of symbols in the kindergartners (
Among all trials, two kindergartners were not able to comply with the instructions during word steering, and thus, their data were removed.
Global MT (
In the primary school group, the linear fitting between ID and MT was significant for all children, except one in the square task. In the kindergarten group, all children obtained significant fitting for the square, whereas 15/19 circles and 15/17 word fittings were significant (
The RMSE of symbol fitting (
The IP (
A tablet-based app to investigate handwriting difficulties through serious games was developed and validated. Standard consumer technology, which does not require supervision and is suitable for home or school use, was leveraged to increase the usability and accessibility of the devised tool. The app was designed to quantitatively characterize the three principles underlying handwriting of isochrony, homothety, and speed-accuracy tradeoff in not only word writing but also symbol drawing, with the final aim of anticipating the screening procedure for handwriting alterations in the preliteracy stage.
To verify that isochrony, homothety, and speed-accuracy tradeoff hold on a tablet surface during word writing, the app was tested on 15 typically developing third graders. Results showed that the tablet surface did not affect the presence of these laws for cursive word writing.
Specifically, isochrony was verified, as writing bigger always increases speed and writing smaller has the opposite effect. This confirms the results reported by Pagliarini et al [
Additionally, the homothety principle holds on the tablet surface, as it was respected in 38 out of 40 cases during cursive writing. Neither writing size nor speed showed a relevant effect on the percentage of time dedicated to each letter with respect to the total word duration, with the only exception of one letter in the
Finally, the speed-accuracy tradeoff principle was confirmed while writing on the tablet surface, since the steering law on words reached significance for 14 out of 15 primary school children. Importantly, these results support our proposal to leverage the steering law to study the speed-accuracy tradeoff during handwriting, which was never performed previously.
The above results support the use of tablet technology to quantitatively assess handwriting production. This is an important achievement, as previous research revealed that changing the writing surface is challenging for writers. Although literature reports an increase in writing speed resulting from the low friction coefficient of the tablet surface [
To detect possible handwriting alterations at an early stage, we investigated whether the principles underlying word writing hold also for symbol drawing in 15 typically developing third graders. Concerning isochrony, we found that it held for symbols. Indeed, isochrony-related speed modulation was observed for all symbols.
Results on homothety further support the possibility to replace a word with a sequence of symbols. Indeed, homothety regarding symbols was confirmed in 29 out of 30 cases. Our results showed that the principle of homothety is even stronger for a sequence of symbols than for a cursive word. An analogy can be found with the work of Pagliarini et al [
As for the speed-accuracy tradeoff for symbols, the linear regression of MT on ID was found to be relevant in 29 out of 30 trials.
Thus, we can conclude that symbols are valid candidates to substitute words and anticipate the study of possible violations of the principles, typical of dysgraphia.
Finally, we tested our app among 19 kindergartners to investigate if and how handwriting maturation affects the skills and laws underlying handwriting. Speed modulation and fraction time preservation were confirmed among kindergarteners during symbol drawing in 100% of cases, supporting that adherence to the isochrony and homothety principles when writing on a tablet surface does not develop as a consequence of mastering handwriting [
Among kindergartners, the speed-accuracy tradeoff was studied while steering both symbols and a cursive word, since we hypothesized that path guidance was a valid help in task execution even before writing acquisition. Our findings showed that the linear regression of MT on ID was significant in the majority of cases (
The steering law parameters revealed a developing trend with age. In particular, kindergartners needed more time to complete the speed-accuracy exercises than older children. This result seems to contradict the group invariance of the average speed obtained when copying symbols (copy game in the
Finally, a higher RMSE emerged for kindergartners during symbol drawing, suggesting that adherence to the steering law is a process that is refined with age. In primary school children only, the RMSE for word tracing was significantly higher than that for symbol tracing (
In conclusion, we proposed a simple tool to quantify the degree of deviation from physiological handwriting, which could help with the objective detection of dysgraphic alterations. The tool exploits serious games to assess important rhythmic principles of handwriting, such as isochrony, homothety, and speed-accuracy tradeoff. It does not require any professional equipment or professional supervision, making the assessment simple and accessible in nonclinical environments. Importantly, we proved that it is possible to start evaluating characteristics underlying handwriting in preschoolers through the use of symbols, which makes the evaluation language independent. Eventually, the tool can provide interesting insights on graphomotor abilities correlated with handwriting and can be used to monitor their evolution over time. Thus, the proposed tool paves the way toward a new model of care. It includes the screening of preliteracy skills to identify potential difficulties before they arise and offers continuous, accessible, and low-cost monitoring of their evolution.
Copy game: sequence.
Tunnel game: word.
Index of difficulty calculation.
Statistical test results for the copy game.
Statistical test results for the tunnel game.
confidence interval
index of difficulty
index of performance
interquartile range
movement time
root mean square error
This study was partly funded by the European H2020 project Movecare (H2020-ICT-2016-1; g.a. 732158).
None declared.