Children with autism spectrum disorders (ASD) often show difficulties in controlling letter size and consistent letter formation during handwriting; however, there has been little research into the underlying nature of handwriting impairments in this group. The aim of this study was to assess the ability of children with ASD to regulate the size and consistency of fundamental handwriting movements when using writing guides, and determine whether the kinematic profile during writing is different to typically developing children. Twenty-six boys with ASD (16 with high-functioning autism, 10 with Asperger's disorder) aged 8–13 years (IQ > 75), and 17 typically developing children wrote a series of four cursive letter l's using 10 mm and 40 mm writing guides, using a graphics tablet and stylus. Movement size and consistency was comparable between groups when the writing guides were set at 10 mm; however, handwriting movements of children with ASD were significantly faster and more fluent than typically developing children when writing guides were set at 40 mm. Neuromotor noise was comparable to that of typically developing children across both writing sizes. Clinically, our findings indicate that children with ASD have a well-automated motor plan for simple handwriting movements when writing guides are present and that problems of handwriting legibility in ASD are likely to arise from other factors, such as complex motor chaining (i.e. writing whole words and sentences), or attentional, working memory and linguistic demands when writing.
Autism spectrum disorder (ASD) is characterized by impaired social interaction and communication, and repetitive and stereotyped behaviors and interests (American Psychiatric Association, 2013). In addition to these deficits, children with ASD often experience impairments in motor functioning (Fournier, Hass, Naik, Lodha, & Cauraugh, 2010). In particular, more than half of elementary school aged children with ASD receive occupational assistance for fine motor control problems (Cartmill et al., 2009 and Church et al., 2000), with handwriting problems shown to persist into adolescence (Fuentes, Mostofsky, & Bastian, 2010) and adulthood (Beversdorf et al., 2001). Despite this, very few studies have examined the underlying nature of handwriting difficulties in ASD (Cartmill et al., 2009 and Kushki et al., 2011, Hellinckx, Roeyers, & Van Waelvelde, 2013) or the impact of occupational therapy interventions (Pennington & Delano, 2012). Handwriting impairments, such as difficulty maintaining consistent letter formation and size, have been consistently reported in studies of handwriting in ASD (Cartmill et al., 2009, Fuentes et al., 2009, Kushki et al., 2011, Hellinckx et al., 2013 and Johnson et al., 2013).
Simple loops of different sizes, such as l and e, are the basic motor unit for all cursive writing, which can be chained together to form more complex letters and whole words ( Plamondon & Guerfali, 1998). When the motor plan is poorly formed, this will manifest as an impaired ability to control the consistency of writing size and shape, as well as movement dynamics, such as movement duration, velocity, and neuromotor noise. Neuromotor noise can be considered the natural variability inherent in the motor system. Where motor control is impaired or inefficient, the motor profile will be characterized by a failure to inhibit this inherent neuromuscular variability. We have recently demonstrated that children with ASD display macrographic handwriting movements and increased neuromotor noise in the absence of writing guides that may reflect difficulties with the internal regulation of the motor plan for basic handwriting movements ( Johnson et al., 2013). To better understand why children with ASD have difficulty controlling the size and consistency, and consequently overall legibility of their handwriting, the aim of this study was to investigate how visual cues, such as writing guides, affect the integrity of fundamental handwriting movements.
We firstly assessed the ability of children with ASD to control the size, shape and dynamics (duration, velocity profile) of simple handwriting movements (cursive letter l's) between writing guides of a well-practiced size (10 mm) when compared to control children. Secondly, to further examine the ability to control handwriting size, we also assessed motor constancy in children with ASD. Motor constancy describes how, in typically developing individuals, when writing at different sizes the overall shape and letter formation (trajectory) and movement dynamics remain relatively constant and only the size will change ( Phillips, Ogeil, & Best, 2009). To explore this, we asked participants to write cursive l's at a larger, less practiced size (between 40 mm writing guides), but which can still be performed using the same effectors, i.e. fingers and wrist. This task has previously been used to investigate motor constancy in children with ADHD ( Langmaid, Papadopoulos, Johnson, Phillips, & Rinehart, 2013), and other motor disorders such as Parkinson's disease ( Caligiuri, Teulings, Filoteo, Song, & Lohr, 2006). Based on previous studies that visual cues improve gait variability in children with ASD ( Rinehart et al., 2006), specifically stride length and consistency, we predicted that writing guides across different sizes would constrain writing size and consistency. Based on findings of continuous circle drawing at various sizes in adults with ASD by Fleury, Kushki, Tanel, Anagnostou, and Chau (2013), a task which is similar to writing cursive l's, we predicted that there would be no difference in neuromotor noise between groups as assessed by power spectral density analysis. However, in line with previous studies of upper limb kinematics in children with ASD ( Dowd et al., 2012, Glazebrook et al., 2009 and Johnson et al., 2013), we predicted that control of overall movement dynamics (velocity, motor smoothness) would be atypical in children with ASD.
