Properties of graphic motor plans in the writing system

ABSTRACT

The present study explores the extent to which properties of abstract graphemic representations are maintained at the post-graphemic level of graphic motor plans, where the sequences of writing strokes for producing the letters in a word are represented. On the basis of results from a stroke patient (NGN) who has a deficit affecting the activation of graphic motor plans, we explore the post-graphemic representation of 1) consonant/vowel status of letters; 2) geminate (double) letters, such as the BB in RABBIT; and 3) digraphs, such as the SH in SHIP. Through analyses of NGN’s letter substitution errors, we conclude that 1) consonant–vowel status is not represented at the level of graphic motor plans; 2) geminates have special representations at the motor-plan level, as at the graphemic level; and 3) digraphs are represented by two separate single-letter graphic motor plans, and not by unitary digraph motor plans.

KEYWORDS:

• Acquired dysgraphia
• peripheral dysgraphia
• writing
• motor plan

Acknowledgements

The author reports there are no competing interests to declare, and no conflict of interest. Correspondence should be addressed to Michael McCloskey, Department of Cognitive Science, Krieger Hall, Johns Hopkins University, Baltimore, MD 21218 USA (Email: [email protected]).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 We did not attempt to match geminate and control words on C/V status of the geminate and control letters, because our results indicate that C/V status is not represented at the graphic-motor-plan level at which NGN’s errors arise, and there is no theoretical motivation for assuming that C/V status would play a role in processing at this level. Hence, for example, controls for the second B in RABBIT included not only CARBON, but also TREBLE.

2 The results in Table 3 do suggest that the probability of a repeated error may be higher the smaller the number of intervening letters: The probability of the same error on both letters decreased from .21 to .02 as the number of intervening letters increased from 1 to 3. This pattern suggests that when attempts are made to activate the same graphic motor plan on two separate occasions, the process is more likely to go awry in the same way on both occasions the closer in time the two attempts are. However, the very large difference between the .97 probability of a repeated error for geminate letters and the .21 probability in cases with an intervening letter suggests that the geminate result does not reflect two separate attempts to retrieve the graphic motor plan (one for each geminate letter), but rather from a process that activates the graphic motor plan once, and uses this plan to drive production of both letters in the geminate.

3 In an earlier study focused primarily on representation of orthographic geminates, Tainturier and Caramazza (1996) found only non-significant differences for patient FM in analyses comparing digraphs and control letter clusters.

4 The digraph pairs were AI, AU, AW, AY, CH, CK, DG, EA, EI, EO, EU, EW, EY, GH, IA, IE, IO, IU, KN, MB, MN, NG, OA, OE, OI, OU, OW, OY, PH, SH, TH, UA, UE, UI, UY, WH, and WR. Several additional letter pairs occur occasionally as digraphs in English (e.g., GN, PS), but these pairs did not appear as digraphs in the stimulus words presented to NGN and so were not considered in the analysis.

Additional information

Funding

This research was supported by a grant from the Johns Hopkins Science of Learning Institute.