Coarticulation in Fluent Fingerspelling

Abstract

In speech, the phenomenon of coarticulation (differentiation of phoneme production depending on the preceding or following phonemes) suggests an organization of movement sequences that is not strictly serial. In the skeletal motor system, however, evidence for comparable fluency has been lacking. Thus the present study was designed to quantify coarticulation in the hand movement sequences of sign language interpreters engaged in fingerspelling. Records of 17 measured joint angles were subjected to discriminant and correlation analyses to determine to what extent and in what manner the hand shape for a particular letter was influenced by the hand shapes for the preceding or the following letters. Substantial evidence of coarticulation was found, revealing both forward and reverse influences across letters. These influences could be further categorized as assimilation (tending to reduce the differences between sequential hand shapes) or dissimilation (tending to emphasize the differences between sequential hand shapes). The proximal interphalangeal (PIP) joints of the index and middle fingers tended to show dissimilation, whereas at the same time (i.e., during the spelling of the same letters) the joints of the wrist and thumb tended to show assimilation. The index and middle finger PIP joints have been shown previously to be among the most important joints for computer recognition of the 26 letter shapes, and therefore the dissimilation may have served to enhance visual discrimination. The simultaneous occurrence of dissimilation in some joints and assimilation in others demonstrates an unprecedented level of parallel control of individual joint rotations in an essentially serial task.

Reorganization of Finger Coordination Patterns During Adaptation to Rotation and Scaling of a Newly Learned Sensorimotor Transformation

“…hand postures can be captured by a small number of independent principal components (PCs) (Jerde et al 2003b;Santello et al 1998Santello et al , 2002. Briefly, subjects donned the data glove and performed three repetitions of a random sequence of 24 hand postures corresponding to the static finger spelling characters of the American Manual Alphabet (AMA).…”

Limb versus Speech Motor Control: A Conceptual Review

“…Jerde et al (2003a) evaluated the impact of coarticulation in finger spelling by measuring movements of fingers and wrist. They found forward and reverse influences across finger-generated letters analogous to the patterns found in speech.…”

Fingerspelling Recognition through Classification of Letter-to-Letter Transitions

“…Modeling transitions results in a recognition system that leverages information available while a letter is being formed to disambiguate between letters whose handshapes appear similar in single-camera video. Additionally, because the letter transition model includes multiple HMM states for each letter depending on the surrounding context, it can learn differences in handshape caused by coarticulation [23].…”