Analysis of Handwriting Fluency in Children with Autism

Background: Children with autism spectrum disorders (ASD) experience difficulty performing a host of skilled motor behaviors, including handwriting (Fuentes et al., 2009; Fuentes et al., 2010). In learning to write, children develop fluidity in handwriting which minimizes the interference of motor demands with higher-order cognitive processes related to composition, and thus, the dynamics of writing account for a large portion of variance in composition fluency (Graham et al, 1997). Despite the recognition of handwriting impairment in ASD and the known importance of handwriting to academic as well as social and communicative growth, there has been little systematic examination of the dynamics of handwriting in children with ASD.

Objectives: The aim of this study was to investigate the dynamic mechanisms underlying writing impairment in children with ASD compared to typically developing (TD) children, which will help to inform the development of effective methods for handwriting remediation.

Methods: Writing performance was assessed using a digitizing tablet (Wacom Intuos4) in sixteen children, 8 with ASD and 8 TD, ages 8-12. Groups were balanced for gender, age, and perceptual reasoning. Each participant completed the Minnesota Handwriting Assessment (MHA) on the digitizing table under three conditions: normal copy, trace, and fast trace. Position and pressure of the pen tip were recorded at a sampling rate of 100 Hz. Using Matlab, handwriting data were segmented using pen pressure to demarcate time spent on and off of the tablet. For each segment, duration, pressure, and total distance traveled were extracted to calculate three dependent variables: speed, fluidity (number of inflection points in speed or decelerations/accelerations), and pen pressure variability.  Significance of group differences in handwriting kinematics was assessed using Mann-Whitney U Tests and the relationship between handwriting kinematics and Movement Assessment Battery for Children, version 2 (mABC-2) score was investigated using Pearson’s correlations.

Results: Regardless of writing condition, children with ASD showed significantly more speed inflections per segment compared to TDs (p < .001 for all three conditions).  There were no significant group differences in mean segment speed or pen pressure variability on any of the conditions. Within the ASD group, higher mABC-2 Manual Dexterity scores were correlated with fewer speed inflections per segment for ASD subjects across conditions (R = -.8, p =.017 for all conditions).

Conclusions: Children with ASD show decreased fluidity of movements during handwriting, regardless of whether copying or tracing letters.  This increased tendency to change speed while writing letter segments may indicate that handwriting is less automated in children with ASD (Mai and Marquardt 1992). Alternatively, it may indicate less stable pen control, particularly given that decreased fluidity was correlated with manual dexterity in children with ASD.  Further investigation using additional metrics (e.g., letter form) and using novel letter forms will help to clarify the basis of these findings.