On the Simultaneous Processing of Words, Letters and Strokes in Handwriting: Evidence For a Mixed Linear and Parallel Model

The Role of Imitation, Primitives, and Spatial Referent Coordinates in Motor Control: Implications for Writing and Reading

We review a body of literature related to the drawing and recognition of geometrical two-dimensional linear drawings including letters. Handwritten letters are viewed not as two-dimensional geometrical objects but as one-dimensional trajectories of the tip of the implement. Handwritten letters are viewed as composed of a small set of kinematic primitives. Recognition of objects is mediated by processes of their creation (actual or imagined)-the imitation principle, a particular example of action-perception coupling. The concept of spatial directional field guiding the trajectories is introduced and linked to neuronal population vectors. Further, we link the kinematic description to the theory of control with spatial referent coordinates. This framework allows interpreting a number of experimental observations and clinical cases of agnosia. It also allows formulating predictions for new experimental studies of writing.

A deficit in post-graphemic writing processes: Evidence for a graphomotor buffer

Post-graphemic writing processes transform abstract letter representations into representations of writing movements. We describe an individual with an acquired post-graphemic writing deficit. NGN is normal in spelling words aloud, but impaired in writing words to dictation, with most errors involving letter substitutions (e.g., RUMOR written as BUMOR). NGN's deficit affects graphic motor plans, which specify the writing strokes for producing letters. Analyses of writing speed, fluency, and stroke patterns suggest that NGN's errors result from incomplete motor-plan activation. NGN's error rate is high for the first letter in a word, and declines across subsequent positions. On the basis of this serial position effect and other results, we propose that post-graphemic writing mechanisms include a graphomotor buffer, a writing-specific working memory that holds activated graphic motor plans bound to specific serial positions. We suggest that NGN's graphomotor buffer is damaged such that early serial positions are affected most severely. Finally, we present results speaking to the roles and capabilities of the graphomotor buffer, and the structure of graphic motor plans.

Impact of handwriting training on fluency, spelling and text quality among third graders

As recent studies and theoretical assumptions suggest that the quality of texts composed by children and adolescents is affected by their transcription skills, this experimental field trial aims at investigating the impact of combined handwriting/spelling training on fluency, spelling and text quality among normally developing 3rd graders (N = 175). In addition to the combined handwriting/spelling training group, the sample includes two other intervention groups, a handwriting training group and a spelling training group as well as a reading fluency training control group. The participating teachers (N = 11) and their students were randomly assigned to the different intervention and control conditions, which were scheduled to last 20 units (each unit lasts 15 min) distributed over 5 weeks (4 units/week). Data collection was administered both before (pre-test) and after (post-test) the intervention as well as 3 months later (follow-up). Measures included group-administered tests and tasks (spelling, visuo-motor integration, copy task, and composing) and individually administered tests and tasks (working memory and several handwriting tasks on the digitizing tablet). As handwriting automaticity (measured on the digitizing tablet) was already high at the beginning of the study, the intervention was not able to improve it further. In consequence, an intervention effect on the quality of composed texts was not observed. Instead, text quality was predicted by working memory, fluency, spelling, and gender irrespective of the intervention.

How do movements to produce letters become automatic during writing acquisition? Investigating the development of motor anticipation

Learning how to write involves the automation of grapho-motor skills. One of the factors that determine automaticity is motor anticipation. This is the ability to write a letter while processing information on how to produce following letters. It is essential for writing fast and smoothly. We investigated how motor anticipation processes build up during the period of handwriting automation. Children aged 8, 9 and 10 years had to write two letters ( ll, le, ln) in cursive writing on a digitizer. Motor anticipation referred to processing changes in size ( ll vs. le) and rotation direction ( le vs. ln) of the second letter while writing the l. We recorded three measures on the l upstroke and downstroke. The movement time data indicate that the l upstroke was very variable. The l’s downstroke duration was shorter for ll than le and the latter was in turn shorter than ln. This pattern was already observed at age 8. Trajectory length data revealed that the anticipation of a single parameter such as size change is enough to produce a trajectory increase but the addition of parameters is not cumulative, as we observed for stroke duration. The dysfluency data indicated that at age 8, dysfluency values were equivalent for upstrokes and downstrokes. At ages 9 and 10, the children produced more dysfluency on downstrokes than upstrokes. Previous studies on writing with adults have shown that the anticipation of the following letter affects the production of the l’s downstroke. The production of the upstroke did not vary. This experiment suggests that learning to anticipate in handwriting production requires: a) rendering the movements to produce the upstroke constant; and b) modulating the downstroke as a function of the spatial characteristics of the following letter. The pattern of movement time data suggest that motor anticipation would start to be adult-like at around age 9. Dysfluency and latency measures do not seem to be very informative about the development of motor anticipation in handwriting.

Handwriting Fluency in Children

This cross-sectional study aimed to (1) construct a model of handwriting fluency in children and (2) explore the impact of fluent handwriting and visual-motor integration on orthographic skills. In a Swiss sample of 93 fourth graders (mean age = 10 years, 7 months; SD = 6.58 months), handwriting speed and legibility were assessed by means of a copying task. Furthermore, automaticity of handwriting, stroke pressure, and stroke frequency were measured on a digitizing tablet, while visual-motor integration and orthographic skills were assessed by means of standardized tests. SEM modeling revealed that automaticity of handwriting, which is associated with both stroke frequency and stroke pressure, predicts handwriting speed as well as orthographic skills. The latter association remained significant even when visual-motor integration, which also proved to be a predictor of orthographic skills, was included in the model. The results are discussed with respect to theories that assume that the automaticity of handwriting is associated with saving cognitive resources.

Processing complex graphemes in handwriting production

Recent studies on handwriting production and neuropsychological data have suggested that orthographic representations are multilevel structures that encode information on letter identity and order, but also on intermediate-grained processing units such as syllables and morphemes. This study on handwriting production examined whether orthographic representations also include a graphemic-processing level. French adults wrote words containing an embedded one-, two-, or three-letter grapheme (e.g., a in clavier, ai in prairie, ain in plainte) on a digitizer. The results for letter duration revealed that the timing of movement processing depends on grapheme length (e.g., the duration of a for one-letter graphemes was shorter than that for two-letter graphemes, which, in turn, was shorter than that for three-letter graphemes). Two- and three-letter graphemes start to be processed before we start to write them. The results therefore revealed that orthographic representations also encode information on grapheme complexity.

Effects of spatial and motor demands in handwriting

Four experiments were conducted to study response programming in handwriting tasks. Twelve right-handed subjects wrote acoustically presented words and phrases, and their handwriting was digitally recorded. Changes in latency, movement time, trajectory length, and pen pressure were studied as a function of response complexity (i.e., word length, complexity of initial letter, and spacing distance). The lengthening of the spatiotemporal parameters preceding the more complex structures is interpreted to be a reflection of the effects of mental load. The results further indicate that the choice of a programming strategy is dependent on the structural complexity of the task. Writing pressure decreased as a function of increased sequence length. The findings support a hierarchical model of handwriting.

Transcoding zeros within complex numerals

This paper describes a patient (LD) showing a selective syntactic deficit in the production of Arabic numerals. Unlike in previously reported cases, LD's syntactic difficulties result in deletions rather than insertions of zeros, with a reduction of the number magnitude. The pattern of errors highlighted a distinction between "lexical zeros", i.e. the zeros in tens, that are semantically derived, and "syntactic zeros" that are syntactically produced as the result of specific production rules. In LD, only syntactic zeros were affected. Furthermore, the processing of numerals with final zeros was found to be easier than the processing of numerals with internal zeros. This pattern of errors is compatible with the lexical-semantic model of Power and Dal Martello. In this model, in fact, lexical zeros originate from a numerical concept, while syntactic zeros originate from a concatenation operation, plus an overwriting operation leaving one or more intermediary zeros. Thus, lexical zeros may be easier to manipulate than syntactic zeros that merely represent a null quantity associated to a specific power of 10.

Verbal structure of numerals and digits handwriting: new evidence from kinematics

Two experiments used a digitizing tablet to analyse the temporal, spatial, and kinematic characteristics of handwritten production of arabic numbers. They addressed a specific issue of the numerical domain: Does the lexical and syntactic structure of verbal numerals influence the production of arabic numerals (Experiments 1 and 2), even after enforced semantic processing in a comparison task (Experiment 2)? Subjects had to write multi-digit arabic numerals (e.g., 1200) presented in two different verbal structures: a multiplicative one (e.g., teen-hundred, douze cents (twelve hundred)) or an additive one (e.g., thousand-unit-hundred, mille deux cents (one thousand two hundred)). Results show differences in the inter-digit jumps that reflect the influence of the structure of verbal numerals, even after the semantic task. This finding is discussed with regard to different models of number transcoding (McCloskey, Caramazza, & Basili, 1985; Power & Dal Martello, 1990, 1997).

Detecting anticipatory events in handwriting movements

We investigated how visual processes exploit specific anticipatory movements observed in handwriting gestures. Previous research has shown that the kinematic information contained in the downstroke of an l is exploited to predict the identity of the forthcoming letter. Here, we determined the moment at which prediction takes place. Two between-letter effects were examined: changes in size (ll vs le) and changes in rotation direction (le vs ln). Results show that with only 75% of the l downstroke trajectory (or 60% of the downstroke time) subjects are already capable of predicting the identity of the letter following the l, that is well before the end of the downstroke. Analysis also reveals that identification takes place after the presentation of the movement acceleration phase. The visual perception of motor anticipation seems to involve the detection of motor events.

Perceptual anticipation in handwriting: the role of implicit motor competence

In two experiments, perceptual anticipation--that is, the observer's ability to predict the course of dynamic visual events--in the case of handwriting traces was investigated. Observers were shown the dynamic display of the middle letter l excerpted from two cursive trigrams (lll or lln) handwritten by one individual. The experimental factor was the distribution of the velocity along the trace, which was controlled by a single parameter, beta. Only for one value of this parameter (beta = 2/3) did the display comply with the two-thirds power law, which describes how tangential velocity depends on curvature in writing movements. The task was to indicate the trigram from which the trace was excerpted--that is, to guess the letter that followed the specific instance of the l that had been displayed. In Experiment 1, the no answer option was available. Experiment 2 adopted a forced-choice response rule. Responses were never reinforced. When beta = 2/3, the rate of correct guesses was high (Experiment 1, P¿correct¿ = .69; Experiment 2, P¿correct¿ = .78). The probability of a correct answer decreased significantly for both smaller and larger values of beta, with wrong answers becoming predominant at the extremes of the range of variation of this parameter. The results are consistent with the hypothesis that perceptual anticipation of human movements involves comparing the perceptual stimulus with an internal dynamic representation of the ongoing event.

Do hyperactive children have motor organization and/or execution deficits?

Hyperactive children have been described as motorically clumsy. To explore the validity of this assertion, an experiment using the additive factor method was designed to examine motor organization and execution in hyperactive children. Four groups of boys aged 7 to 8 years took part in the study: (1) a pure hyperactive (HA) group, N=20; (2) a pure conduct-disordered (CD) group, N=18; (3) a mixed hyperactive/conduct-disordered (HA+CD) group, N=12; (4) a normal (N) control group, N=22. While the small sample size precluded a definitive conclusion, the results indicated that neither HA nor CD children showed any motor organization or execution deficit in a simple sequential key-tapping task. Given previous findings indicating that hyperactive children show deficits in more complex motor coordination skills, the generalizability of our negative results needs to be examined on other more complex tasks.

A Forthcoming Key Press Can Be Selected While Earlier Ones Are Executed

The possibility that a key press can be selected during execution of earlier key presses and the resulting pattern of interferences were investigated in this study. Subjects (N equals 26) were required to press a series of keys, determined in advance, before they pressed a stimulus-dependent key. Response selection demands were manipulated by using spatially compatible and incompatible SndashR mappings because S-R compatibility is well known to not disappear with practice. The longer time needed to select an incompatible key vanished when the choice key was preceded by two or four predetermined key presses. Only early in practice did the time to press the first and the choice key in a three-key sequence exhibit part of the compatibility effect. With limited practice, concurrent preparation in the three-key sequence was relatively slow and took longer than the time required for executing the fixed keys. These findings suggest that processes involved in execution are not affected by concurrent response selection and that one of the effects of practicing movement sequences is that later movements can be selected while earlier ones are being executed. This need not affect execution rate. Therefore, different degrees of concurrent processing are not always reflected in reduced execution rates.

Practice and the Dynamics of Handwriting Performance

Sixteen adult subjects were served in an experiment in which the writing of six unfamiliar graphemes was practiced. To investigate the learning process, we analyzed the absolute and relative changes of movement time of the first three consecutive segments as a function of practice. The results showed that movement time of all three segments decreased. This decrease was significantly less in the first segment that it was in the second and third segment, however. We interpret these effects of practice, from an information-processing viewpoint, as follows: (a) Initially separate response segments become integrated in more comprehensive response chunks, and (b) the preparation of later segments of the grapheme is realized more and more during the real-time execution of the initial segment. The results further revealed that these learning effects were more pronounced in graphemes composed of familiar segments than in graphemes that contained unfamiliar segments. Finally, it turned out that similarity between initial and final segments hindered the writing speed of the first segment; the effect of similarity was independent of the above-mentioned effects of practice. The latter effect is interpreted as confirming evidence for the view that the preparation of later segments of a grapheme is reflected by changes of movement time of the first segments of a grapheme.