Adapting to the surface: A comparison of handwriting measures when writing on a tablet computer and on paper

Our study addresses the following research questions: Are there differences between handwriting movements on paper and on a tablet computer? Can experienced writers, such as most adults, adapt their graphomotor execution during writing to a rather unfamiliar surface for instance a tablet computer?We examined the handwriting performance of adults in three tasks with different complexity: (a) graphomotor abilities, (b) visuomotor abilities and (c) handwriting. Each participant performed each task twice, once on paper and once on a tablet computer with a pen.We tested 25 participants by measuring their writing duration, in air time, number of pen lifts, writing velocity and number of inversions in velocity. The data were analyzed using linear mixed-effects modeling with repeated measures.Our results reveal differences between writing on paper and on a tablet computer which were partly task-dependent. Our findings also show that participants were able to adapt their graphomotor execution to the smoother surface of the tablet computer during the tasks.     

Similarity of tactual and visual picture recognition with limited field of view.

Subjects attempted to recognize simple line drawings of common objects using either touch or vision. In the touch condition, subjects explored raised line drawings using the distal pad of the index finger or the distal pads both of the index and of the middle fingers. In the visual condition, a computer-driven display was used to simulate tactual exploration. By moving an electronic pen over a digitizing tablet, the subject could explore a line drawing stored in memory; on the display screen a portion of the drawing appeared to move behind a stationary aperture, in concert with the movement of the pen. This aperture was varied in width, thus simulating the use of one or two fingers. In terms of average recognition accuracy and average response latency, recognition performance was virtually the same in the one-finger touch condition and the simulated one-finger vision condition. Visual recognition performance improved considerably when the visual field size was doubled (simulating two fingers), but tactual performance showed little improvement, suggesting that the effective tactual field of view for this task is approximately equal to one finger pad. This latter result agrees with other reports in the literature indicating that integration of two-dimensional pattern information extending over multiple fingers on the same hand is quite poor. The near equivalence of tactual picture perception and narrow-field vision suggests that the difficulties of tactual picture recognition must be largely due to the narrowness of the effective field of view.     

An Apple microcomputer-based laboratory system for the study of visual-motor behavior

An apparatus for studying motor control and visual-motor coordination is described. The system consists of an Apple II+ with two expansions boards installed. One board provides advanced graphics capabilities; the other interfaces the Apple with a digitizing tablet and also provides a real-time clock. Target stimulus and visual feedback concerning self-produced movement (i.e., a cursor) are displayed on a standard video monitor, and movement data are sampled by the digitizing tablet. Software consists of about 3K bytes of assembled 6502 code and a 2K byte Applesoft BASIC program. The system is inexpensive, versatile, and particularly well suited for developmental research. It has been used with human subjects as young as 3 years of age.     

An inexpensive videoprojection/digitization system for behavioral research

We present an inexpensive approach to image analysis of spatial coordinates for behavioral research. Image analysis of still video images (freeze frames) with current technology can be prohibitively expensive, as well as time consuming. The system outlined here provides an accurate, inexpensive, and fast approach to acquiring information from videotape. It consists simply of a video monitor, bellows, large diameter lens, and a digitizing tablet. The images are projected onto a digitizing tablet, and data acquisition is controlled with a series of three functions written in APL. We used this system to acquire positional information on fish responding to the threat of aerial predation. We discuss several approaches to design and construction of this system, as well as provide computer listings for initiation of communication with digitization boards.     

Selective reaching: distracter effects on movement kinematics as a function of target-distracter separation

The authors investigated distracter effects on the kinematics of reaching movements to determine when during reaching responses (reaction time, time to peak velocity, time after peak velocity, or peak velocity) distracter interference occurred and how target-distracter separation affected the locus of interference. Participants moved a pen on a digitizing tablet toward a target appearing with or without a distracter. With a small target-distracter separation, distracter interference occurred during time after peak velocity (similar amounts of interference from near and far distracters). With a large target-distracter separation, distracter interference occurred during time to peak velocity (more interference from near compared to far distracters). The results demonstrated that target-distracter separation is an important determinant of the locus of distracter interference.     

A low-cost method for digitizing videotaped continuous movements on the Macintosh

We describe an inexpensive means of digitizing videotaped positions of moving points, such as the positions of the joints of a person who is performing an action. Single-frame video images and a Macintosh computer monitor are optically superimposed, using a half-silvered mirror, and the positions of reference points in the video image are manually clicked in by the operator, so that the screen coordinates of the reference points on each frame can be stored in a text file for later analysis. The digitizing program records comments and identifying information along with the position data.     

Individual and group modelling of aesthetic judgment strategies

Individual differences in aesthetic judgments were investigated by comparing quantitative group and individual performance models of the judgment processes. Aesthetic judgments of beauty over novel, formal, graphic patterns were collected from 34 non‐artist college students using a two‐step ranking‐rating procedure. Their judgment processes were individually modelled using Judgment Analysis. The participants showed noted individual differences. Certain features of the stimulus material, which were considered to contribute to the picture's beauty by one participant, were used in an opposing fashion by another. A group model was derived based on the average ratings of the patterns' beauty. It was concluded that the group model was not an adequate representation of the present data, whereas the data revealed systematic judgment processes at the individual subject level.     

STRUCTURE IN SIMILARITY MATRICES

Waern, Y. Structure in similarity matrices. A graphic approach. Scand. J. Psychol ., 1972, 13 , 5–16.—The present paper proposes a simple method for representing the structure inherent in the similarity matrix, i.e. a graphic representation. The traditional multidimensional scaling methods are compared with each other and with the graphic representation with regard to representation, interpretation and assumptions concerning the subject's performance. The graph gives a topological representation and the derivation of the graph from the similarity matrix may be made so as to reduce the demands on the subjects somewhat. As to interpretation, the graph is able to reveal dimensions, clusters, and hierarchies. Compared with some multidimensional scaling it gives very similar interpretations.     

Visual dominance in amending the directional parameter of feedforward control

The authors examined visual dominance between trials in which the movement program was amended (i.e., off-line processing). Weighting between visual and proprioceptive feedback was examined in a trial-by-trial analysis of the directional parameter of feedforward control. Eight participants moved a cursor to a target displayed on a computer screen by manipulating a hand-held stylus on a digitizing tablet. In the first 30 trials, the cursor followed the stylus movement (practice condition). In the next 30 trials, the directional error of the stylus movement was presented in the opposite direction (reversal condition). Subjects knew the presence and the nature of the reversal. In the last 10 trials, the reversal was withdrawn (transfer condition). Directional error of feedforward control was relatively small in the practice condition, and it increased gradually in 1 of 2 directions as trials proceeded in the reversal condition. Positive aftereffect was observed in the transfer condition. A constant increment of the directional error indicated that both visual and proprioceptive feedback are registered, with higher weight on vision, and that weighting between those inputs is determined automatically or is fixed without any strategic control.     

Visual Dominance in Amending the Directional Parameter of Feedforward Control

The authors examined visual dominance between trials in which the movement program was amended (i.e., off-line processing). Weighting between visual and proprioceptive feedback was examined in a trial-by-trial analysis of the directional parameter of feedforward control. Eight participants moved a cursor to a target displayed on a computer screen by manipulating a hand-held stylus on a digitizing tablet. In the first 30 trials, the cursor followed the stylus movement (practice condition). In the next 30 trials, the directional error of the stylus movement was presented in the opposite direction (reversal condition). Subjects knew the presence and the nature of the reversal. In the last 10 trials, the reversal was withdrawn (transfer condition). Directional error of feedforward control was relatively small in the practice condition, and it increased gradually in 1 of 2 directions as trials proceeded in the reversal condition. Positive aftereffect was observed in the transfer condition. A constant increment of the directional error indicated that both visual and proprioceptive feedback are registered, with higher weight on vision, and that weighting between those inputs is determined automatically or is fixed without any strategic control.     

What happens to an individual visual working memory representation when it is interrupted?

This study tested the hypothesis that even the simplest cognitive tasks require the storage of information in working memory (WM), distorting any information that was previously stored in WM. Experiment 1 tested this hypothesis by requiring observers to perform a simple letter discrimination task while they were holding a single orientation in WM. We predicted that performing the task on the interposed letter stimulus would cause the orientation memory to become less precise and more categorical compared to when the letter was absent or when it was present but could be ignored. This prediction was confirmed. Experiment 2 tested the modality specificity of this effect by replacing the visual letter discrimination task with an auditory pitch discrimination task. Unlike the interposed visual stimulus, the interposed auditory stimulus produced little or no disruption of WM, consistent with the use of modality‐specific representations. Thus, performing a simple visual discrimination task, but not a simple auditory discrimination task, distorts information about a single feature being maintained in visual WM. We suggest that the interposed task eliminates information stored within the focus of attention, leaving behind a WM representation outside the focus of attention that is relatively imprecise and categorical.     

Submovement Organization,Pen Pressure,and Muscle Activity Are Modulated to Precision Demands in 2D Tracking

The authors investigated how tracking performance, submovement organization, pen pressure and muscle activity in forearm and shoulder muscles were affected by target size in a 2D tracking task performed with a pen on a digitizer tablet. Twenty-six subjects took part in an experiment, in which either a small dot or a large dot was tracked, while it moved quasirandomly across a computer screen at a constant velocity of 2 cm/s. The manipulation of precision level was successful, because mean distance to target and the standard deviation of this distance were significantly smaller with the small target than with the large target. With a small target, subjects trailed more behind the center of target and used submovements with larger amplitudes and of shorter duration, resulting in higher tracking accuracy. This change in submovement organization was accompanied by higher pen pressure, while at the same time muscle activity in the forearm extensors and flexors was increased, indicating higher endpoint stability. In conclusion, increased precision demands were accommodated by both a different organization of submovements and higher endpoint stability in a 2D tracking task performed with a pen on a digitizer tablet.     

MODELING PROBABIUSTIC CATEGORIZATION DATA:

Abstract— In probabilistic categorization tasks, the correct category is determined only probabilistically by the stimulus pattern Data from such experiments have been successfully accounted for by a simple network model, but have posed difficulties for exemplar models In the present article, we consider an exemplar model, CLEM (concept learning by exemplar memorization), which differs from previously tested exemplar models in that exemplar traces are assumed to be stored only when the subject has guessed or made a classification error Fits of CLEM to both learning and test data were comparable to those of the network model, and better than those obtained for a version of CLEM in which encoding was independent of the subject's response The implications of these results for the processes underlying classification decisions are discussed.     

客体同维度特征的视觉工作记忆存储机制

客体理论认为视觉工作记忆的存储单位是客体, 人类能够把组成物体的所有特征整合成一个单元进行记忆, 不管这些特征是来自不同维度还是同一维度。然而同一维度多个特征可以被整合成客体记忆的结果只被少数研究证实, 大量研究发现同一维度的多个特征不能被整合记忆, 这形成了弱客体理论的基本观点。为了解决两大理论之间的争议, 本研究主要探究同维度特征能否被整合记忆。通过分析以往研究, 我们认为实验范式和物体意义两个因素可能是导致之前大部分研究没有发现维度内特征能够被整合记忆的原因。因此, 实验1采用回忆报告范式替代以往研究经常使用的变化觉察范式, 结果发现, 同一维度的多个特征难以被整合记忆。实验2以记忆无意义物体的特征为基线, 探究在记忆有意义物体的特征时是否可能将多个特征进行整合记忆。结果发现, 对于有意义物体的特征的记忆成绩并没有显著好于记忆无意义物体特征的成绩, 说明即使采用具有较强整合线索的有意义物体作为载体, 同一维度多个特征也难以被整合记忆。两个实验结果进一步支持了弱客体理论。     

Can computer mice be used as low-cost devices for the acquisition of planar human movement velocity signals?

The main goal of this work is to determine whether a computer mouse can be used as a low-cost device for the acquisition of two-dimensional human movement velocity signals in the context of psychophysical studies and biomedical applications. A comprehensive overview of the related literature is presented, and the problem of characterizing mouse movement acquisition is analyzed and discussed. Then, the quality of velocity signals acquired with this kind of device is measured on horizontal oscillatory movements by comparing the mouse data to the signals acquired simultaneously by a video motion tracking system and a digitizing tablet. A synthesis of the information gathered in this work indicates that the computer mouse can be used for the reliable acquisition of biosignals in the context of human movement studies, particularly for many applications dealing with the velocity of the end effector of the upper limb. This paper concludes by discussing the possibilities and limitations of such use.     

Effects of stimulus omission and stimulus change on dishabituation of the skin conductance response

Three experiments examined the effects of stimulus omission and stimulus change on dishabituation of the skin conductance response. In all experiments, subjects received 17 tone-light or light-tone (S1-S2) pairings, and the primary manipulations were omission of and change in S2 on Trial 16. Responses to S1 and S2 on Trial 17 constituted the data of primary interest. Experiment 1 (N = 72) demonstrated that omission of an expected stimulus was more effective in producing dishabituation than was presentation of an unexpected but not experimentally novel stimulus. Experiment 2 (N = 60) indicated that both omission of an expected stimulus and presentation of an unexpected and experimentally novel stimulus produced dishabituation. Experiment 3 (N = 72) revealed that both the omission and the miscuing of 52 produced reliable dishabituation. The results are interpreted as indicating the importance of a comparison between current input and the stored representation of previous stimulation in the development of habituation.     

The effects of reordering the response categories on the area under the ROC

The area under the rating ROC can be a useful index of stimulus discriminability. It has the advantage that few assumptions must be made about the underlying distributions of signal and noise. One of the assumptions that must be made is the order of the subject’s response scale. A procedure is outlined for determining the order of the response scale actually used by the subject, and some of the implications of reordering the scale used in analysis are discussed. Results of computer simulation of the effects of varying some important experimental parameters are presented.     

Evaluating models of collinearity judgment for reliability and scale.

In prior work from this laboratory, we have examined how accurately subjects can judge collinearity, i.e. alignment, as a function of the angular position of stimulus elements. In those experiments, subjects were presented with a line segment (or a pair of dots) which varied across the 360 degrees range of angular positions, and were required to select and mark a point which was perceived as being collinear. We found that the models of error for each subject consisted of a complex set of peaks and valleys which are herein described as delta excursions. The error tendencies appeared to be idiosyncratic, in that each subject manifested a different profile of these excursions. Here we report the results of three experiments. In the first, we tested subjects across five sessions, and found that the five models of error were fairly comparable for a given subject. In the second and third experiments, we tested at close intervals of angular position, and found evidence for localized sources of error. We continue to find that the error model for each subject is idiosyncratic, and argue that the excursions may be due to defects in a system which combines responses from position-encoding fields that vary in size.     

Effect of postural instability on drawing errors in children: a synchronized kinematic analysis of hand drawing and body motion

To investigate the role that postural stability plays in fine motor control, we assessed kinematics of the head, shoulder, elbow, and the pen during an accuracy drawing task in 24 children. Twelve children were classified into an accurate drawing (AD) group and 12 children into an inaccurate drawing (ID) group based on a manual dexterity task from the movement assessment battery for children [Henderson, S. E., & Sugden, D. A. (1992). Movement assessment battery for children. London: Psychological Corporation.]. Their parents completed a questionnaire to assess children's inattention, hyperactivity, and impulsivity. An electromagnetic tracking system was used to monitor 3-D kinematic data of the body parts, while 2-D kinematic data of pen movement was simultaneously collected from a computer digitizer tablet. If a sudden body motion (1cm/s) occurred within a time window from one second prior to the onset of the drawing error to the end of the error, we considered that the error coincided with the extraneous body movement. For each drawing trial, the coincidence rate was computed as (number of coincidences)/(number of errors). The ID group had a significantly higher coincidence rate of head and shoulder movements compared with elbow movements, whereas coincidence rates did not differ between the three body parts in the AD group. Parental ratings of children's behavioral ratings of inattention, hyperactivity, and impulsivity were not correlated with the coincidence rates. The results indicated that inaccurate drawing was a result of postural instability rather than fidgeting caused by inattention or hyperactivity/impulsivity.     

Sensitivity to shifts of a point stimulus: An instance of tactile hyperacuity

The sensitivity of the tactile sense to shifts in the position of a point stimulus was determined at four body loci: the index finger, forehead, belly, and back. Water-jet stimulation was used, a method which allows frictionless travel of a point stimulus over the skin. Three subjects were tested by means of the method of forced choice, with the task being to say whether the stimulus moved to the right or to the left. The shift threshold was defined as that shift excursion which gave rise to 75% correct responding. The basic finding was that shift thresholds were on the order of 10 to 30 times smaller than the corresponding two-point limens obtained by Weinstein (1968) for the same body loci. These unexpectedly small shift thresholds indicate an exquisite sensitivity of the cutaneous sense to rapid changes in position of a point stimulus. A physiological model is presented which accounts for the difference between localization and spatial resolution. nt]mis|This research was supported by Department of Health~ Education, and Welfare Grant 14-P-SS282/9 from the Social and Rehabilitation Services, NIH Research Grant R01-EY-00686 from the National Eye Institute, and the Smith-Kettlewell Eye Research Foundation.