Linguistic and perceptual-motor contributions to the kinematic properties of the braille reading finger
Introduction
Relative to visual print reading, the linkages between the perceptual, cognitive, and motor processes of braille reading have not been deeply investigated. It is clear that visual reading and braille reading must share common types of operations: both can be held to involve perceptual information utilization, in letter, morpheme, and word recognition (with attendant demands on attention and memory), as well as the range of syntactic and semantic operations that give text a specific interpretation (Daneman, 1988, Foulke, 1991). In addition, both are highly dependent on concurrent active motor control: via fixations and saccadic eye movements or via finger movements. However, dissimilarities are also clear. As Bertelson, 1995, Millar, 1997 have pointed out, braille reading is held to begin with exhaustive and serial contact with the surface on which the text is embossed and to involve movements that are smoother than saccades and fixations.1 As a consequence, empirically grounded models of braille reading need to show how the fingers move, how the interaction of skin and textured surface gives rise to pattern recognition, and if and how the linguistic processing of the braille code influences these perceptual and motor operations.
Since the finger movements of the braille reader need to be controlled with a degree of precision commensurate with the spatial details of the braille code, as well as the temporal rate at which words, syntax, and semantic content can be processed, analysis of the reading movements would benefit from measurements of higher order variables, such as velocity and acceleration. Consider Panel A of Fig. 1. When reading a line of text with a single dominant finger, the position of a braille reader’s dominant reading finger is highly linear when plotted as a function of time. That is, the dominant finger tends to move continuously from left to right, with contact maintained between skin and text surface. Similar position-by-time data have been reported previously (see, e.g., Bertelson et al., 1985, Millar, 1997, Mousty and Bertelson, 1985). Finger position-by-time plots suggest that braille reading is “smooth, with few variations in speed” (Bertelson, 1995, p. 94).
However, when the position data can be differentiated with respect to time, a measure of the instantaneous velocity of the finger as it crosses text becomes available (Fig. 1B). Such computations reveal that the finger rapidly alternates between phases of acceleration and deceleration and that there is considerable variability of velocity about the mean. Finger velocity tends to be neither constant nor smooth. Such an intermittent2 profile is by no means peculiar to this trial; it is representative of all readings of all sentences by all individuals that we have recorded.
To what processes should such intermittencies be attributed? A priori, those exemplified in Fig. 1B can be attributed to more than one source. The fluctuations might originate by virtue of skin contact with textured surfaces – that is, in haptic texture perception. Raised dots of the braille code are, at this level, differentially rough surfaces that may well generate position-based fluctuations in the friction quotient. These fluctuations in resistance to movement across the surface might also impact the discharge of cutaneous receptors and proprioceptive afferents, and therefore motor efference, all of which characterize haptic explorations of texture (e.g., Hughes and Jansson, 1994, Katz, 1925–1989, Loomis and Lederman, 1986).
A second possibility is that, at the speeds characteristic of braille, the limb motor control system simply cannot generate either constant or smooth velocity profiles at the distal fingertips, even if that is the intent of readers. Intermittent velocity traces may be an emergent feature of finger movements that are slow enough to permit letter and word recognition but not fast enough to constitute singular trajectories.
It may be that the intermittency of the velocity profile is owing to fluctuations in the ongoing demands of linguistic comprehension. Do the kinematics of the movements of braille readers similarly reflect the instantaneous demands of text perception and processing in a manner that is comparable with print reading? Perhaps unfamiliar letter combinations, or rare words, or sentences of complex syntax, or unpredictable content have the effect of briefly reducing the velocity of the moving finger to accommodate longer lexical search, or parsing operations, or semantic processing. Psycholinguistic factors are known to have consistent effects on the patterns of eye fixations and saccades in visual reading (for recent reviews, see Kliegl et al., 2006, Rayner, 1998) and hence it would not surprise if there were analogous language processing modulations of reading movements in braille.
Our major objective was to investigate how each of these factors contributes to the kinematic profiles of the reading finger. First, we sought to establish the extent to which the kinematic characteristics of movements of the fingerpad over braille text are influenced by the texture composition of the braille cells, independently of needing to be read. We did this by asking readers to scan “as smoothly as possible” a single line of meaningless braille text comprised of repeated braille cells with zero, one, three, or five raised elements. We hypothesized that the velocity of scanning movements would be higher and the intermittency lower than during reading because there were no requirements to process text at any level. If the texture composition of braille cells influences the kinematics of finger movements, we expected to find text with more raised cells to create more resistance to smooth left–right movements and lines containing no raised cells at all to be scanned with the smoothest velocity profiles.
To measure text processing effects on finger kinematics, we created sentences that varied in two ways: by comprising either high- or low-frequency key words, which were embedded in sentences with or without meaning. If language processing demands are directly reflected in finger kinematics, then we should observe reduced mean velocities, more intermittent velocities, and more frequent reversals when reading sentences with low-frequency words. We examined these hypotheses in conjunction with two others. We asked whether second readings of sentences were faster and smoother than first readings, and whether the benefit of a second reading was greater for sentences with low-frequency words and/or sentences without semantic content. If first readings are slowed and made more intermittent by vagaries of lexical access or a lack of semantic context, is this true for second readings where memory for – and hence anticipation of – text is possible? In addition, we required readers to read either silently, so as to be able to repeat verbatim the contents of the sentences at completion of reading, or to read out-loud. These tasks differ primarily in their working memory demands (greater for silent reading) and their phonological encoding (greater for reading aloud but not absent in silent reading). Silent and oral reading have been found to differ in their visual reading characteristics: fixation durations tend to be longer and saccade lengths shorter in oral reading (see Rayner, 1984). Millar (1990) found that braille readers of all levels of experience were no faster on average reading aloud than silently. We sought a replication of this finding, while leaving open the possibility that the reading modes would have the different effects on finger movement kinematics, including velocity intermittency.
Section snippets
Participants
Twelve fluent braille readers (10 females; 2 males) provided informed consent under protocols approved by the University of Auckland Human Participants Research Committee and the Institutional Review Board of Arizona State University. Ten participants were congenitally blind; two lost their sight completely at age 10 y. Their ages ranged from 27 y to 75 y (mean: 44.9 ± 14.0 y). On average, participants began reading braille at 7.8 y (±4.2 y) although three did not begin reading braille until later (at
Smooth scanning
The participants were asked to scan lines of meaningless text “as smoothly as possible”, the purpose of which was to determine exactly how smooth “smooth movements” can be generated by braille readers. Velocity plots upon which the following analyses are based are shown in Fig. 2. These plots indicate that braille readers cannot easily generate movements that are kinematically smooth even if they are consciously smooth.
Analysis of variance (ANOVA) of mean velocity revealed a significant effect
Discussion
Eye movements have long been considered an important and unobstrusive window onto the cognitive processes associated with reading (e.g., Just and Carpenter, 1980, Rayner, 1998, Rayner and Sereno, 1994, Underwood, 1985) as well as reading disorders such as dyslexia (e.g., Pollatsek, 1983). The measurement of saccade timing and fixation durations is central to understanding the functional characteristics of saccades and fixations in reading which, in turn, constitute major points of difference in
Acknowledgments
This research was supported from grants from the University of Auckland Research Committee and the Royal Society of New Zealand (Bilateral Research Assistance Programme) to the first author and the research was conducted while he was Visiting Research Scholar at Arizona State University. Portions of the research were presented at the 20th Annual Convention of the Association for Psychological Science, Chicago (May 2008) and the European Conference on Visual Perception, Utrecht University,
References (44)
- et al.
Central neural mechanisms contributing to the perception of tactile roughness
Behavioural and Brain Research
(2002) - et al.
Relationship between hand movements, reading competence and passage difficulty in braille reading∗
Neuropsychologia
(1980) - et al.
Origins of submovements during pointing movements
Acta Psychologica
(2008) - et al.
Roughness coding in the somatosensory system
Acta Psychologica
(1993) - et al.
Texture perception via active touch
Human Movement Science
(1994) - et al.
Finger movements in braille reading: The effect of local ambiguity
Cognition
(1992) Computational models of eye-movement control during reading: Theories of the “eye-mind” link
Cognitive Systems Research
(2006)Language by touch: The case of braille reading
- et al.
A study of braille reading: 2. Patterns of hand activity in one-handed and two-handed reading
Quarterly Journal of Experimental Psychology
(1985) - et al.
The time course of braille word recognition
Journal of Experimental Psychology: Learning, Memory and Cognition
(1992)
Enlightened: The art of finger reading
Studia Linguistica
Visual attention and word recognition in Stroop color naming: Is word recognition automatic?
Journal of Experimental Psychology: General
Comprehension processes in braille reading
Journal of Visual Impairment & Blindness
Temporal cues contribute to tactile perception of roughness
Journal of Neuroscience
Neural coding of tactile texture: Comparison of spatial and temporal mechanisms for roughness perception
Journal of Neuroscience
How reading braille is both like and unlike reading print
Memory & Cognition
Intermittency in preplanned elbow movements persists in the absence of visual feedback
Journal of Neurophysiology
Braille
The intermittency of the braille reading finger velocities
Cited by (17)
The effect of hand movements on braille reading accuracy
2017, International Journal of Educational ResearchCitation Excerpt :Regressions may range from one or two braille characters until a number of words (Papadopoulos, 2005) and they are performed with gentle movements at relatively high speeds (Hughes, 2011). One or two hands move backwards for a short time without fingers rising from the braille characters, in order to reread something that was not detected by the initial scanning (Hughes et al., 2011), to control or/and to regulate tactile reading (Mousty & Bertelson, 1992). Alternatively, it may be the second phase of forward scanning (Millar, 1997).
Behavioural and Electrophysiological effects related to semantic violations during braille reading
2015, NeuropsychologiaCitation Excerpt :At no point during the movements did the pen tip contact the raised dots. These methods of recording the reading finger replicated earlier work (e.g., Hughes et al., 2011; Hughes et al., 2009). Trials were segmented for analysis using a TTL pulse as a “trigger”.
Parallel versus sequential processing in print and braille reading
2012, Research in Developmental DisabilitiesEncoding/decoding of first and second order tactile afferents in a neurorobotic application
2011, Journal of Physiology ParisStructure of variability in scanning movement predicts braille reading performance in children
2021, Scientific Reports