Control of goal-directed movements: the contribution of orienting of visual attention and motor preparation.

Three experiments investigated the role of attention and motor preparation for the control of goal-directed movements. In Experiment 1 (double step paradigm), a movement correction was required on 25% of the trials towards the left or right of the initial target. Within these 25% of trials, the probability of location of the second target was manipulated. The efficiency of movement control increased when increasing the probability of correcting the movement in a given direction. In Experiment 2, attentional processes were isolated by asking the subjects to verbally detect the more or less probable target displacement, without correcting their movement. Subjects were able to orient visual attention during movement execution, thus improving the processing of visual feedbacks from target displacement. In Experiment 3, motor preparation processes were isolated by asking the subjects to correct their movement towards a fixed target in response to a more or less probable mechanical perturbation. It was shown that motor preparation not only specifies the initial movement parameters but may also include some parameters of the most probable movement modulations. Overall, these results highlight the role of both attentional and motor preparation processes in the control of goal-directed movements and suggest that the feedback-based corrections of the movement are modulated by a feedforward control.     

Hide-and-seek around the centre of interest: The dead zone of attention revealed by change blindness

Three experiments examined spatial allocation of attention during active search for visual changes. In all experiments, there were three conditions of change location related to a centre of interest: (1) Central (most attended location itself), (2) near, and (3) far marginal change. In Experiment 1, participants showed the slowest search and the largest number of undetected changes in near condition. Moreover, they misidentified near changes more frequently than central and far ones. In Experiment 2, participants had to search for marginal changes in the presence of a once noticed central change that summoned additional attention to a central location. It resulted in further search slowing for near changes. In Experiment 3, participants searched for one of two concurrent marginal changes in the presence of a central one. They detected far changes about 2.3 times more frequently than near ones. Taken together, these results support the notion of “dead zone of attention” surrounding attentional focus. Several speculations about the nature of dead zone are discussed.     

Mood-induced self-focused attention.

The influence of mood on self-focused attention was explored in 2 experiments involving the induction of moods in the laboratory. Experiment 1 tested the hypothesis that mood states, whether pleasant or unpleasant, induce self-focused attention. This hypothesis was supported using a sentence completion task as the measure of self-focus. Experiment 2 replicated Experiment 1 results using a measure of self-complexity as an index of self-focus. These experiments provide support for a model of affect-action sequences the first step of which entails the turning of attention toward the self in response to the arousal of affect.     

Splitting focal attention.

The study was based on the inverse relationship between the effect of attention on reaction time (RT) and the size of the area over which focal attention is allocated. Independent occurrence of this in 2 locations in the opposite hemifields would be evidence of attention splitting. In Experiment 1, in which the 2 locations were denoted by empty boxes, there was an inverse relationship between size of the stimulated box and RT. Experiment 2 replicated the finding with different stimulation conditions. In Experiment 3, no relationship was found between RT and length of a cuing line. In Experiment 4, in which attention was manipulated by central cues, there was an effect of box size on valid and neutral trials but not invalid trials. Observers could split focal attention and manipulate simultaneously 2 independent attentional foci on objects located in the opposite hemifields.     

Reallocation of visual attention.

Attentional movement time was investigated within and across hemifields in a discrimination task in which retinal acuity was controlled. Ss discriminated targets in a two-alternative, forced-choice latency paradigm. In Experiments 1-3, costs were mediated by distance, even though it was varied independently of acuity. In Experiments 4 and 7, with distance held constant, costs were equivalent for crossing the vertical and horizontal meridians and for crossing 1 and 2 meridians. However, crossing 1 meridian produced costs that were less than the costs for shifts to unexpected locations in the same quadrant, partially replicating the inhibitory aftereffect of Tassinari, Aglioti,Chelazzi,Marzi,and Berlucchi (1987). An explanation based on a combination of analog movement (Tsal, 1983) and attentional distribution (Downing & Pinker, 1985; Hughes & Zimba, 1987; Tassinari et al., 1987) models was discussed.     

Two-pulse temporal integration functions in the fovea and peripheral retina

The temporal integration of luminous energy was compared in the fovea and at 7 degrees eccentricity using two-pulse stimuli and two methodologies. The two-pulse stimuli consisted of two 1-msec. light pulses separated by intervals of darkness ranging from 1 to 400 msec.; they were provided by a glow modulator tube transilluminating a 21.8' opal glass target. In Exp. 1 (equal-performance design), integration functions were generated using a forced-choice staircase procedure to estimate threshold luminance. The data for two Os showed that the critical duration (CD), and thus the period of complete integration, was briefer in the fovea than at 7 degrees. Beyond the CD, integration continued to differ for the two retinal locations. In the fovea, two-pulse stimuli beyond CD evidenced partial integration and at the longest stimulus durations no integration or inhibition. In contrast, at 7 degrees stimuli beyond CD appeared to evidence probability summation. In Exp. 2 (equal-energy design), integration functions were generated by measuring the detectability of two-pulse stimuli of different durations but equal in total luminous energy. A signal-detection procedure yielded measures of both response frequency and signal detectability, P(A). The data for two Os showed that for both measures CD was briefer in the fovea than at 7 degrees. Also, in the fovea, long two-pulse stimuli appeared to show no integration or inhibition. Both experiments then showed a foveal-peripheral difference in two-pulse measures of visual temporal integration, with the fovea evidencing less integration. In addition, the forced-choice and signal-detection procedures showed that these loci differences in integration were independent of the Os' response criterion.     

Frequency response characteristics for sinusoidal movement in the fovea and periphery

Threshold sensitivity was measured for sinusoidal movement of bright 1-deg lines against a dark background as a function of oscillation frequency and retinal location. Sensitivity was greatest in the fovea and at a frequency of 1–2 Hz. Peripheral sensitivity was more narrowly tuned than foveal sensitivity. The presence of a stationary reference line affected mainly the foveal sensitivity. The results are interpreted as evidence for both position- and velocity-sensitive mechanisms in the movement detection system.     

Drawing attention to meaning.

The engineering of displays that adapt to particular tasks, users, and/or contexts depends on insight into how display content is processed and understood. There are different levels at which content carries meaning, and this paper sets out a model of how these levels of meaning are integrated within human information processing. Such a model is important in establishing a principled basis for adaptation; in particular, it identifies the critical role of a highly schematic level of representation in mediating interpretation of content. The role of this level in effecting forms of adaptation is discussed, and used to argue why recent work at the overlap between graphics and semantic web technologies may now provide a suitable foundation for delivering adaptive and minimal graphics in practice.     

Age similarities in the inertial properties of attention.

Adult age differences in the mode of allocation of visual attention were investigated, using a visual search task with a circular display containing one target letter and seven distractor letters. In two experiments, a total of 56 younger adults (M = 20 years) and 56 older adults (M = 66 years) searched for a target appearing with equal probability at one of two cued locations. The first cue appeared 115 msec before display onset, and the second cue appeared with display onset; distance between the two cued locations was varied. Target identification performance indicated that attention was inertial, in that reaction time for second-cued targets was related either to the area of the portion of the visual field containing possible target locations or to the mean path length of a serial self-terminating search. There were no age-related decrements in the allocation of visual attention.     

Recent developments in the study of tactile attention.

The last few years have seen a rapid growth of research on the topic of tactile attention. We review the evidence showing that attention can be directed to the tactile modality, or to the region of space where tactile stimuli are presented, in either an endogenous or exogenous (top-down or bottom-up) manner. We highlight the latest findings on the interaction between these two forms of attentional orienting in touch. We also review the latest research on tactile numerosity judgments and change detection highlighting the severe cognitive (attentional) limitations that constrain people's ability to process more complex tactile information displays. These findings are particularly important given that tactile interfaces are currently being developed for a number of different application domains.     

Reducing the effects of adjacent distractors by narrowing attention.

Three experiments explored the gradual narrowing of visual attention to a letter target when other letters were positioned close by. The method by which attention was narrowed involved presenting a digit target immediately prior to the latter target and in the same location for progressively shorter durations and requiring the subject to identify both the digit target and the letter target before responding. The response time data from the first 2 experiments indicated that shorter durations of the digit reduced the amount of information processed from noise letters positioned on either side of the letter target. In the third experiment, in which separation of letters was increased slightly, the response times indicated that the information from flanking noise letters may have been virtually eliminated.     

Infant attention and the development of smooth pursuit tracking.

The effect of attention on smooth pursuit and saccadic tracking was studied in infants at 8, 14, 20, and 26 weeks of age. A small rectangle was presented moving in a sinusoidal pattern in either the horizontal or vertical direction. Attention level was distinguished with a recording of heart rate. There was an increase across age in overall tracking, the gain of the smooth pursuit eye movements, and an increase in the amplitude of compensatory saccades at faster tracking speeds. One age change was an increase in the preservation of smooth pursuit tracking ability as stimulus speed increased. A second change was the increasing tendency during attentive tracking to shift from smooth pursuit to saccadic tracking when the stimulus speed increased to the highest velocities. This study shows that the development of smooth pursuit and targeted saccadic eye movements is closely related to the development of sustained attention in this age range.     

The spatial resolution of visual attention.

Two tasks were used to evaluate the grain of visual attention, the minimum spacing at which attention can select individual items. First, observers performed a tracking task at many viewing distances. When the display subtended less than 1 degrees in size, tracking was no longer possible even though observers could resolve the items and their motions: The items were visible but could not be individuated one from the other. The limiting size for selection was roughly the same whether tracking one or three targets, suggesting that the resolution limit acts independently of the capacity limit of attention. Second, the closest spacing that still allowed individuation of single items in dense, static displays was examined. This critical spacing was about 50% coarser in the radial direction compared to the tangential direction and was coarser in the upper as opposed to the lower visual field. The results suggest that no more than about 60 items can be arrayed in the central 30 degrees of the visual field while still allowing attentional access to each individually. Our data show that selection has a coarse grain, much coarser than visual resolution. These measures of the resolution of attention are based solely on the selection of location and are not confounded with preattentive feature interactions that may contribute to measures from flanker and crowding tasks. The results suggest that the parietal area is the most likely locus of this selection mechanism and that it acts by pointing to the spatial coordinates (or cortical coordinates) of items of interest rather than by holding a representation of the items themselves.