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H.j. Woltring, Fax/tel +31.40.413 744
09-08-1992, 11:11 PM
Dear Biomch-L readers,

One of our long-standing subscribers posted the item below onto his own
list this morning; I think that it might also be of interest to Biomch-L.

Enjoy -- hjw.

-----------------------------------

Date: Wed, 9 Sep 92 11:29:00 MET
From: "Hans-Leo Teulings Tel:+31-80-615476 Fax:-615938"
Subject: Invariant properties between stroke features
Sender:
"SCRIB-L Handwriting Production, Recognition, Reading, Education, Expertise"


Dear Scrib-lers,

The following paper can be retrieved by anonymous ftp (or requested by
e-mail from the authors). Feel free to report troubles to hlt@nici.kun.nl.

ftp ftp.nici.kun.nl
anonymous

cd pub/nici/handwriting/teulinvar
mget *
bye


+--------------------------------------------------------------------+
|Accepted: Acta Psychologica, 82, 1993. |
|Submitted: 26 June 1992 |
|Presented: 5th Handwriting Conference: Motor Control of Handwriting,|
| October 27-30, 1991, Tempe, AZ, USA. |
|Title: Invariant properties of handwriting motor programs to be |
| employed in automatic handwriting recognition. |
+--------------------------------------------------------------------+

Invariant properties between stroke features in handwriting

Hans-Leo Teulings & Lambert R.B. Schomaker

Nijmegen Institute for Cognition and Information (NICI) University of
Nijmegen, P.O.Box 9104, 6500 HE Nijmegen, The Netherlands E-mail:
hlt@nici.kun.nl & schomaker@nici.kun.nl, Fax: +31-80-615938

Abstract

A handwriting pattern is considered as a sequence of ballistic
strokes. Replications of a pattern may be generated from a single,
higher-level memory representation, acting as a motor program.
Therefore, those stroke features which show the most invariant pattern
are probably related to the parameters of the higher-level
representation, whereas the more noisy features are probably related
to the parameters derived at the lower levels (top-down hierarchy).
This hierarchy of invariances can be revealed by the signal-to-noise
ratio (SNR), the between-parameter correlations, and the
between-condition correlations. Similarly, at the higher level a
sequence of strokes may act as a unit from which individual strokes
are derived (sequence hierarchy). This hierarchy of invariances can be
revealed by the between-stroke correlation, which forms a weaker
criterion than rescalability, which has been rejected mostly. Previous
research showed that vertical stroke size has higher SNRs and higher
between-condition correlations than stroke duration or peak force,
whereas the latter two features were also negatively correlated. This
suggested that vertical stroke size is a higher-level parameter than
the other two. The present research largely confirmed this
top-down-hierarchy and even for upstrokes and downstrokes separately.
Downstrokes were more invariant than upstrokes in terms of vertical
stroke size. However, contrary to the vertical stroke size, the
horizontal stroke size was not invariant. Both vertical and horizontal
sizes showed substantial between-stroke correlations. In contrast, the
stroke durations did not show any between-stroke correlations. This
suggests that stroke segmentation is reliable in spite of the discrete
sampling of the handwriting movements.