James W. Meehan

Forward/up directional incompatibilities during cursor placement within graphical user interfaces.

Within graphical user interfaces, an indirect relationship between display and control may lead to directional incompatibilities when a forward mouse movement codes upward cursor motions. However, this should not occur for left/right movements or direct cursor controllers (e.g. touch sensitive screens). In a four-choice reaction time task, 12 participants performed movements from a central start location to a target situated at one of four cardinal points (top, bottom, left, right). A 2 × 2 × 2 design varied directness of controller (moving cursor on computer screen or pen on graphics tablet), compatibility of orientation of cursor controller with screen (horizontal or vertical) and axis of desired cursor motion (left/right or up/down). Incompatibility between orientation of controller and motion of cursor did not affect response latencies, possibly because both forward and upward movements are away from the midline and go up the visual field. However, directional incompatibilities between display and controller led to slower movement with prolonged accelerative phases. Indirect relationships between display and control led to less efficient movements with prolonged decelerative phases and a tendency to undershoot movements along the bottom/top axis. More direct cursor control devices, such as touch sensitive screens, should enhance the efficiency of aspects of cursor trajectories.

Conflicting directional and locational cues afforded by arrowhead cursors in graphical user interfaces

Task-irrelevant features of arowhead cursors may generate conflict during cursor placement within graphical user interfaces. Arrowheads can signify location, but also cue direction and feature in optical illusions. To address the influence of conflicting cues, 14 participants used arrowhead cursors (standard, oversized) pointing upward or downward to move to targets (7.5, 15-mm diameter) situated at the top or bottom of the screen. Compatible arrowhead orientation improved response initiation. Cursor size, orientation, direction of motion, and target size interacted during cursor movement. Overshooting occurred for oversized cursors in the direction the arrow pointed for larger targets. Larger compatible arrowhead cursors elicit less efficient cursor positioning movements that are more susceptible to illusory processes, posing implications for design of cursors and graphical user interfaces.

Apparent minification in an imaging display under reduced viewing conditions

When extended outdoor scenes are imaged with magnification of 1 in optical, electronic, or computer-generated displays, scene features appear smaller and farther than in direct view. This has been shown to occur in various periscopic and camera-viewfinder displays outdoors in daylight. In four experiments it was found that apparent minification of the size of a planar object at a distance of 3–9 m indoors occurs in the viewfinder display of an SLR camera both in good light and in darkness with only the luminous object visible. The effect is robust and survives changes in the relationship between object luminance in the display and in direct view and occurs in the dark when subjects have no prior knowledge of room dimensions, object size or object distance. The results of a fifth experiment suggest that the effect is an instance of reduced visual size constancy consequent on elimination of cues for size, which include those for distance.

Visual accommodation as a cue for size

Accommodation micropsia is examined in the general context of ocular accommodation as a cue for object size. The nature and limits of accommodation micropsia and arguments dealing with the possible contribution of accommodation to the perception of size are reviewed. Literature on the anomalous myopias, the intermediate-resting hypothesis, and theories of ciliary muscle innervation is examined critically in so far as it bears on the accommodation-micropsia hypothesis. The anomalous myopias and evidence for the intermediate-resting hypothesis are well documented, but without a mechanism for proprioceptive feedback from the ciliary complex about the state of accommodation it can only be concluded that such feedback would have to be indirect, either via the reflex link with vergence, or possibly through the agency of efference-copy neurones.

Effects of compatibility and turning biases on arrowhead cursor placement in graphical user interfaces

Arrowhead cursors have the potential to generate response conflict, as they are used to signify location but also implicitly cue direction. This study considered the time course of the resolution of any response conflict. The interplay between object properties and action was addressed through consideration of the effects of arrowhead cursor orientation upon action. Twelve participants moved arrowhead cursors of four possible orientations with respect to direction of movement (compatible, incompatible, port, starboard) towards a square (4mm or 8mm) target in a graphical user interface. Kinematic analysis determined if and how an interplay existed between object properties and action. Cursor orientation primarily influenced cursor movement, with the effects manifesting during terminal guidance. The blunt end of an arrowhead cursor was moved faster by users, and there appeared to be turning biases during cursor placement. Arrowheads have a number of properties (vertex, orientation, width) that influence cursor placement in graphical user interfaces.

Pseudophakes Experience Apparent Minification in an Imaging Display

Apparent minification of virtual images has been attributed to accommodation micropsia, that is, a reduction in the apparent size of viewed objects accompanying an inward accommodation of the eyes. Thirteen bilateral pseudophakes incapable of accommodation but with good residual vision were tested monocularly for apparent minification in the viewfinder of a single-lens reflex camera. Apparent minification of about the same order as that typically found with normals occurred with the pseudophakic observers, demonstrating that pseudophakes are subject to distortions in apparent size with virtual-imaging displays in the same way as normals, thus establishing that visual accommodation is not a necessary condition for the effect.

Cursor type and response conflict in graphical user interfaces

Arrowhead cursor shape may offer irrelevant cues that conflict with desired positioning movements. To assist cursor design this study considered how cursor shape can influence the preparation or execution of cursor positioning movements. An experiment varied cursor shape on-line such that its shape cued the required direction of movement or better afforded hitting the target. Twelve participants performed cursor positioning movements with systematic variations in cursor shape affecting preparation (neutral, pre-cuing target direction), cursor flight (arrowhead, comet) and terminal guidance (big, small target). Kinematic analysis determined the effects on phases of cursor placement. Cursor shape primarily affected terminal guidance and implies conventional cursor designs should be reconsidered.

Non-target flanker effects on movement in a virtual action centred reference frame

Visual selective attention is thought to underly inhibitory control during pointing movements. Accounts of inhibitory control during pointing movements make differential predictions about movement deviations towards or away from highly salient non-target flankers based on their potential cortical activation and subsequent inhibition: (1) Tipper et al. (Vis Cogn 4:1–38, 1997) “response vector model” predicts movements away from highly salient flankers; (2) Welsh and Elliott’s (Q J Exp Psychol 57:1031–1057, 2004a and J Mot Behav 36:200–211, 2004b) “response activation model” predicts movements towards highly salient flankers early in the response, that is resolved by a race for inhibition. To eliminate the confounds of physical properties, such as obstacle avoidance and information cues of non-target objects, pointing was conducted in a virtual environment (graphical user interface). Participants were 14 skilled computer users who moved a computer cursor with a mouse to virtual targets. Analysis revealed non-target flankers significantly interfered with movement consistent with action centred selective attention, and reflecting a proximity-to-hand effect. Spatial analysis revealed evidence of highly salient flankers attracting movement, and less salient flankers repelling movement, supporting Welsh and Elliott’s response activation model. These effects were achieved in a virtual 2D environment where interference caused by the physical properties of objects was less cogent.

Two theories of perception: Internal consistency, separability and interaction between processing modes

Comparisons are drawn between two theories of visual perception and two modes of information processing. Characteristics delineating dorsal and ventral visual systems lack internal consistency, probably because they are not completely separable. Mechanism is inherent when distinguishing these systems, and becomes more apparent with different processing domains. What is lacking is a more explicit means of linking these theories.