Yves Guiard

Asymmetric Division of Labor in Human Skilled Bimanual Action: The Kinematic Chain as a Model

This article presents a tentative theoretical framework for the study of asymmetry in the context of human bimanual action. It is emphasized that in man most skilled manual activities involve two hands playing different roles, a fact that has been often overlooked in the experimental study of human manual lateralization. As an alternative to the current concepts of manual preference and manual superiority-whose relevance is limited to the particular case of unimanual actions-the more general concept of lateral preference is proposed to denote preference for one of the two possible ways of assigning two roles to two hands. A simple model describing mans favored intermanual division of labor in the model are the following. 1) The two hands represent two motors, that is, decomplexity is ignored in the suggested approach. 2) In man, the two manual motors cooperate with one another as if they were assembled in series, thereby forming a kinematic chain: In a right-hander allowed to follow his or her lateral preferences, motion produced by the right hand tends to articulate with motion produced by the left. It is suggested that the kinematic chain model may help in understanding the adaptive advantage of human manual specialization.

Stimulus-response compatibility and the Simon effect: toward a conceptual clarification

The current view that the Simon effect (Simon & Small, 1969) reflects stimulus-response compatibility (SRC) is questioned. Previous accounts of the Simon effect have overlooked stimulus congruity (SC), the correspondence relation borne by the two simultaneous aspects of the stimulus, a factor inevitably confounded in the Simon paradigm with irrelevant spatial S-R correspondence. The Hedge and Marsh (1975) reversal effect, replicated in Experiment 1, is reinterpreted as decisive evidence that the Simon effect is entirely accounted for by SC. Furthermore, in Experiment 2 irrelevant S-R correspondence was manipulated in the absence of any variation of SC, and the Simon effect vanished. It is concluded that the Simon effect, contrary to current opinion, represents a spatial variant of the Stroop effect and is irrelevant to the SRC issue. The view that mental operations proceed automatically at the stage of response determination loses one of its strongest empirical arguments.

Human on-line response to target expansion

McGuffin and Balakrishnan (M&B) have recently reported evidence that target expansion during a reaching movement reduces pointing time even if the expansion occurs as late as in the last 10% of the distance to be covered by the cursor. While M&B massed their static and expanding targets in separate blocks of trials, thus making expansion predictable for participants, we replicated their experiment with one new condition in which the target could unpredictably expand, shrink, or stay unchanged. Our results show that target expansion occurring as late as in M&Bs experiment enhances pointing performance in the absence of expectation. We discuss these findings in terms of the basic human processes that underlie target-acquisition movements, and we address the implications for user interface design by introducing a revised design for the Mac OS X Dock.

Clutch-free panning and integrated pan-zoom control on touch-sensitive surfaces: the cyclostar approach

This paper introduces two novel navigation techniques, CycloPan, for clutch-free 2D panning and browsing, and CycloZoom+, for integrated 2D panning and zooming. These techniques instantiate a more generic concept which we call Cyclo* (CycloStar). The basic idea is that users can exert closed-loop control over several continuous variables by voluntarily modulating the parameters of a sustained oscillation. Touch-sensitive surfaces tend to offer impoverished input resources. Cyclo* techniques seem particularly promising on these surfaces because oscillations have multiple geometrical and kinematic parameters many of which may be used as controls. While CycloPan and CycloZoom+ are compatible with each other and with much of the state of the art, our experimental evaluations suggest that these two novel techniques outperform flicking and rubbing techniques.

Watchit: simple gestures and eyes-free interaction for wristwatches and bracelets

We present WatchIt, a prototype device that extends interaction beyond the watch surface to the wristband, and two interaction techniques for command selection and execution. Because the small screen of wristwatch computers suffers from visual occlusion and the fat finger problem, we investigated the use of the wristband as an available interaction resource. Not only does WatchIt use a cheap, energy efficient and invisible technology, but it involves simple, basic gestures that allow good performance after little training, as suggested by the results of a pilot study. We propose a novel gesture technique and an adaptation of an existing menu technique suitable for wristband interaction. In a user study, we investigated their usage in eyes-free contexts, finding that they perform well. Finally, we present techniques where the bracelet is used in addition to the screen to provide precise continuous control over list scrolling. We also report on a preliminary survey of traditional and digital jewelry that points to the high frequency of watches and bracelets in both genders and gives a sense of the tasks people feel like performing on such devices.

MicroRolls: expanding touch-screen input vocabulary by distinguishing rolls vs. slides of the thumb

The input vocabulary for touch-screen interaction on handhelds is dramatically limited, especially when the thumb must be used. To enrich that vocabulary we propose to discriminate, among thumb gestures, those we call MicroRolls, characterized by zero tangential velocity of the skin relative to the screen surface. Combining four categories of thumb gestures, Drags, Swipes, Rubbings and MicroRolls, with other classification dimensions, we show that at least 16 elemental gestures can be automatically recognized. We also report the results of two experiments showing that the roll vs. slide distinction facilitates thumb input in a realistic copy and paste task, relative to existing interaction techniques.

The lateral coding of rotations: a study of the simon effect with wheel-rotation responses.

A number of experimental studies have consistently shown the locus of spatial S-R compatibility effects to be the selection of the response within an abstract memory code. The purpose of the present study was to test, in the particular case of wheel rotations, the general proposition that any response that a subject internally codes in terms of left and right may be interfered with by the lateral location of the stimuli in a Simon paradigm. Experiment 1 showed that the auditory Simon effect occurred in a task where the subjects had to rotate a steering wheel bimanually either clockwise or counterclockwise according to sound pitch, despite the fact that responses of this kind are undefined with respect to laterality. Experiment 2 confirmed this result in a unimanual rotation condition and suggested that the ear-rotation compatibility effect may be added to the effect of a biomechanical factor, pronation versus supination, supporting the idea of an abstraction motor code. In Experiment 3, subjects rotated the steering wheel with their hands on the lowest part of the wheel. When the response movement made the spot of a C.R.T. move laterally in accordance with the performed rotation, the subjects coded their response directly in terms of its effect on the visual display. For subjects not receiving visual feedback, no compatibility effect occurred. however, the individual data were compatible with the notion that some subjects in this group coded their responses in terms of wheel rotations, and others in terms of hand movements.

Two-handed performance of a rhythmical fitts task by individuals and dyads.

The authors investigated 4 variants of a reciprocal Fitts task in which the pointer was moved to a stationary target, the target was moved to a stationary pointer, or both the pointer and the target were moved to each other bimanually; the bimanual task was carried out either by a single person or by a dyad. Fittss law held in all 4 conditions, with only minor parametric changes. The kinematic organization varied with task difficulty but remained invariant in task space (i.e., in the mutual frame of reference of the pointer-target system) whatever the pointing condition. In the bimanual conditions, the 2 effectors were coordinated in antiphase with compensatory variability. The authors suggest that the observed chronometric and kinematic patterns emerge from an interplay between simple harmonic motion and the stabilizing influence of the informational flow generated by the closing of the gap between the pointer and the target interval.

Navigation as multiscale pointing: extending Fitts' model to very high precision tasks

Fitts pointing model has proven extremely useful forunderstanding basic selection in WIMP user interfaces. Yet todaysinterfaces involve more complex navigation within electronicenvironments. As navigation amounts to a form of multi-scalepointing, Fitts model can be applied to these more complex tasks.We report the results of a preliminary pointing experiment thatshows that users can handle higher levels of task difficulty withtwo-scale rather than traditional one-scale pointing control. Also,in tasks with very high-precision hand movements, performance ishigher with a stylus than with a mouse.

Beyond the 10-bit Barrier: Fitts' Law in Multi-Scale Electronic Worlds

Multi-scale interfaces make it possible to investigate Fitts’ law beyond 10 bits, so far an inviolable barrier of difficulty. We hadcomputer users, equipped with a zoom, point at visual targets whose index of difficulty (ID) varied between 3 and 30 bits. The zoom was ignored for easy targets and began to be used at ID = 8bits, with zooming amplitude then increasing linearly with the ID. A linear, zero-intercept Fitts’ law equation was found to accurately model target acquisition time throughout our extended spectrum of IDs. Some implications of these findings for human-computer interaction and basic research are discussed.