Models for the generation of writing units in handwriting under variation of size, slant, and orientation

In a split second: Handwriting pauses in typical and struggling writers

Introduction

A two-second threshold has been typically used when analyzing the writing processes. However, there is only a weak empirical basis to claim that specific average numbers and durations of pauses may be associated with specific writing processes. We focused on handwriting execution pauses, because immature writers are known to struggle with transcription skills. We aimed to provide an evidence-based account of the average number and duration of handwriting pauses in the mid-Primary grades and to identify process-level markers of writing difficulties.

Methods

Eighty 3rd and 5th graders, with and without writing difficulties, participated in the study. We examined pauses in a handwriting-only task, to be able to isolate those which could only be attributed to handwriting processes. Letter features were considered, as well as children's handwriting fluency level.

Results

The average duration of handwriting pauses was around 400ms, in line with assumptions that transcription pauses would fall under the 2,000ms threshold. We found that 3rd graders made more and longer pauses than 5th graders. Struggling writers made a similar number of pauses across grades than typically-developing children, although they were significantly longer, even after controlling for the effect of handwriting fluency.

Discussion

Our findings provide an evidence-based account of the duration of handwriting pauses. They also suggest that children need fewer and shorter handwriting pauses as they progress in automatizing transcription. However, some young writers struggle with letter formation even after 3 to 5 years of instruction.

Circadian rhythm in handwriting

The aim of the present study was to determine whether the motor process of handwriting is influenced by a circadian rhythm. Nine healthy young male subjects underwent a 40-h sleep deprivation protocol under constant routine conditions. Starting at 09:00 hours, subjects performed every 3 h two handwriting tasks of different complexity. Handwriting performance was evaluated by writing speed, writing fluency and script size. The frequency of handwriting, as a measure of movement speed, revealed a circadian rhythm, validated by harmonic regression, with a slowing at the time of the onset of melatonin secretion (22:17 hours) and a trough in the very early morning at around 03:30 hours. In the temporal variability of handwriting an effect of task complexity was suggested in the direction of circadian variations in parallel with speed only for the sentence. Despite deficits of speed and temporal variability, writing fluency did not change significantly across sessions indicating that the basic automation of handwriting was preserved at any time. On the second day, daytime levels of the kinematics of handwriting did not reflect impaired performance after sleep deprivation. Our results show for the first time a clear circadian rhythm for the production of handwriting.

Authorship effects in the prediction of handwriting strokes: evidence for action simulation during action perception

Does the action system contribute to action perception? Recent evidence suggests that actions are simulated while being observed. Given that the planning and simulating system are the same only when one observes one's own actions, it might be easier to predict the future outcomes of actions when one has carried them out oneself earlier on. In order to test this hypothesis, three experiments were conducted in which participants observed parts of earlier self- and other-produced trajectories and judged whether another stroke would follow or not. When the trajectories were produced without constraints, participants accomplished this task only for self-produced trajectories. When the trajectories were produced under narrow constraints, the predictions were equally accurate for self- and for other-generated trajectories. These results support the action simulation assumption. The more the actions that one observes resemble the way one would carry them out oneself, the more accurate the simulation.

The role of vision in the temporal and spatial control of handwriting

The general observation that handwriting is not noticeably impaired by the withdrawal of vision can be explained in two ways. One might argue that vision is not needed during the act of writing. Micro-analyses should then reveal that spatial as well as temporal writing features are identical in conditions of vision and no vision. Alternatively, it is possible that vision is needed during the act of writing, but that without vision possible errors and inaccuracies have to be prevented. Assuming that the latter would place an extra demand on movement control, this should be revealed by an increase in processing time. We have found evidence for the latter view in the present study in which 12 subjects wrote a nonsense letter sequence with and without vision. Close examination showed that writing shapes remained equally invariant under both vision conditions, suggesting that spatial control was unaffected by withdrawing vision. The prediction that invariance of shapes is preserved in the absence of vision at the expense of processing time increments was confirmed. The increase of reaction time observed when visual guidance was withdrawn suggests that more processing time was needed prior to the movement start. Moreover, the RT increment was larger when a short writing duration was instructed. The present findings will be discussed in light of the remarkable flexibility of writing as a motor skill in which writers appear to be able to employ specific strategies to preserve shape in the absence of visual guidance.