Visual orienting with central and peripheral precues: Deconfounding the contributions of cue eccentricity, cue discrimination and spatial correspondence

Landmark cueing and exogenous (onset) cueing: How are they related?

Attentional consequences of (i) mere onset of a peripheral visual cue, and (ii)encoding spatially predictive, landmark features of that cue were studied in two experiments. Target location was associated with landmark features of peripheral cues. Cue onset elicited both attention capture (Experiment Two) and inhibition of return (Experiment One) effects. In both experiments, attentional effects of landmark features of the cues were observed early in practice, and diminished with time on task. Contrary to hypotheses based on models that liken attention to a moving spotlight or zoom lens, in both experiments attentional effects of landmark features were confined to the location where the cue was presented. To explain this, we enlist the concept of attentional priority maps, and propose that visual encoding causes attentional priorities to be updated via alternative input routes and mechanisms. We suggest that onset cueing effects are associated with retinotectal 'spatial indexing', which registers the location, but not the attributes of new stimuli, while landmark cueing effects are associated with interaction between spatial indexing and dorsal stream visual processing of attentionally relevant landmark features.

The time-course of activation in the dorsal and ventral visual streams during landmark cueing and perceptual discrimination tasks

Different patterns of high density EEG activity were elicited by the same peripheral stimuli, in the context of Landmark Cueing and Perceptual Discrimination tasks. The C1 component of the visual event-related potential (ERP) at parietal - occipital electrode sites was larger in the Landmark Cueing task, and source localisation suggested greater activation in the superior parietal lobule (SPL) in this task, compared to the Perceptual Discrimination task, indicating stronger early recruitment of the dorsal visual stream. In the Perceptual Discrimination task, source localisation suggested widespread activation of the inferior temporal gyrus (ITG) and fusiform gyrus (FFG), structures associated with the ventral visual stream, during the early phase of the P1 ERP component. Moreover, during a later epoch (171-270ms after stimulus onset) increased temporal-occipital negativity, and stronger recruitment of ITG and FFG were observed in the Perceptual Discrimination task. These findings illuminate the contrasting functions of the dorsal and ventral visual streams, to support rapid shifts of attention in response to contextual landmarks, and conscious discrimination, respectively.

Illusory line motion is not caused by object-differentiating mechanisms or endogenous attention

Christie and Klein [2005. Does attention cause illusory line motion? Perception & Psychophysics, 67(6), 1032-1043] published line motion ratings consistent with illusory line motion (ILM) after peripheral endogenous cues but not central arrow cues. When attention was directed endogenously on the basis of the shape of one of two peripherally presented objects, participants reported small, but significant motion away from the attended object, and this was attributed to participant bias, or to a peripherally directed object-based attention system endogenously recruited to differentiate the peripheral shapes. By using a unique cueing method with identical peripheral markers, but still allowing them to act as cues, the findings of Christie and Klein Experiment 4 were replicated. This reduces the likelihood that object discrimination or object attention mechanisms are responsible for the reported ILM-like effects.

Ageing and Visual Orienting in Response to Complex Spatial Cues

An experiment is reported in which young and older adults performed a visual orienting task and a cue discrimination task. In the visual orienting task symbolic cues (letters) provided predictive information concerning the likely location of a target stimulus. Two letters, drawn from a pool of four ‘valid’ and four ‘invalid’ letters, were presented bilaterally, at either central or peripheral locations. In the cue discrimination task participants were presented with the same bilateral letter stimuli, and indicated whether these represented a valid letter on the right with an invalid letter on the left, or vice versa. In the visual orienting task young adults shifted attention appropriately in response to the letter cues, but older adults failed to do this. Older participants also performed more poorly on the cue discrimination task. However, even older participants who performed as well as young participants on the cue discrimination task failed to orient in response to the letter cues. Results are discussed in terms of effects of ageing on the ability to forge functionally effective links between different task components in the course of learning how to perform new perceptuomotor skills.

Adaptive Gaze Control for Object Detection

We propose a novel gaze-control model for detecting objects in images. The model, named act-detect, uses the information from local image samples in order to shift its gaze towards object locations. The model constitutes two main contributions. The first contribution is that the model’s setup makes it computationally highly efficient in comparison with existing window-sliding methods for object detection, while retaining an acceptable detection performance. act-detect is evaluated on a face-detection task using a publicly available image set. In terms of detection performance, act-detect slightly outperforms the window-sliding methods that have been applied to the face-detection task. In terms of computational efficiency, act-detect clearly outperforms the window-sliding methods: it requires in the order of hundreds fewer samples for detection. The second contribution of the model lies in its more extensive use of local samples than previous models: instead of merely using them for verifying object presence at the gaze location, the model uses them to determine a direction and distance to the object of interest. The simultaneous adaptation of both the model’s visual features and its gaze-control strategy leads to the discovery of features and strategies for exploiting the local context of objects. For example, the model uses the spatial relations between the bodies of the persons in the images and their faces. The resulting gaze control is a temporal process, in which the object’s context is exploited at different scales and at different image locations relative to the object.

Orienting of attention with eye and arrow cues and the effect of overtraining

In contrast to the classical distinction between a controlled orienting of attention induced by central cues and an automatic capture induced by peripheral cues, recent studies suggest that central cues, such as eyes and arrows, may trigger a reflexive-like attentional shift. Yet, it is not clear if the attention shifts induced by these two cues are similar or if they differ in some important aspect. To answer this question, in Experiment 1 we directly compared eye and arrow cues in a counter-predictive paradigm while in Experiment 2 we compared the above cues with a different symbolic cue. Finally, in Experiment 3 we tested the role of over-learned associations in cueing effects. The results provide evidence that eyes and arrows induce identical behavioural effects. Moreover, they show that over-learned associations between spatially neutral symbols and the cued location play an important role in yielding early attentional effects.

Does attention cause illusory line motion?

Illusory line motion (ILM) has been shown to occur when a line is presented with one end next to a previously stimulated location. The line appears to be drawn away from the site of stimulation. It has been suggested that this is because of the allocation of attention to the stimulated site. Using an endogenous attentional manipulation (a central arrow cue) with no differences in the display between the two ends of the line at the time of line presentation or immediately prior, no ILM was detected, though there was a small effect in the opposite direction. Those who have found endogenously induced ILM have used an endogenous cue based on a property of a location marker that indicated the cued location. Changing the method of cuing to one based on a property of a peripheral marker instead of a central arrow produced a small but significant report of ILM. The small magnitude of the effect, participant self-reports, and the absence of the effect in the purely endogenous condition, suggest that this was merely a bias. ILM is not generated by endogenous attention shifts.

Sex hormonal modulation of hemispheric asymmetries in the attentional blink

The present study examines differences in functional cerebral asymmetries modulated by gonadal steroid hormones during the menstrual cycle in women. Twenty-one right-handed women with regular menstrual cycles performed a double-stream rapid serial visual presentation (RSVP) task, with one stream in each visual field, during the low steroid menses and the high steroid midluteal phase. They were required to detect a target item, and then a probe item, each of which could appear in either stream. If the probe item appeared 200 ms after the target, detection of the probe was impaired-a phenomenon known as the "attentional blink." This occurred in both streams in the midluteal phase, but only in the right visual field during menses. Thus low steroid levels appeared to restrict the attentional blink to the left hemisphere, while high levels of estradiol and progesterone in the midluteal phase appeared to reduce functional asymmetries by selectively increasing the attentional blink in the right hemisphere. This effect appears to be mediated by estradiol rather than progesterone, and it is compatible with the assumption of a hormone-related suppression of right hemisphere functions during the midluteal phase.

Attention: Reaction Time and Accuracy Reveal Different Mechanisms

The authors propose that there are 2 different mechanisms whereby spatial cues capture attention. The voluntary mechanism is the strategic allocation of perceptual resources to the location most likely to contain the target. The involuntary mechanism is a reflexive orienting response that occurs even when the spatial cue does not indicate the probable target location. Voluntary attention enhances the perceptual representation of the stimulus in the cued location relative to other locations. Hence, voluntary attention affects performance in experiments designed around both accuracy and reaction time. Involuntary attention affects a decision as to which location should be responded to. Because involuntary attention does not change the perceptual representation, it affects performance in reaction time experiments but not accuracy experiments. The authors obtained this pattern of results in 4 different versions of the spatial cuing paradigm.

Do isoluminant color changes capture attention?

Four experiments are reported in which the effects of peripheral cues on visual orienting were investigated. In the luminance condition, the cues consisted of a peripheral change in stimulus luminance. In the isoluminance condition, the cues consisted of an isoluminant color change, using the transient tritanopic technique. In Experiments 1 and 2, it was found that peripheral luminance cues captured attention, whereas peripheral isoluminance cues did not. In Experiments 3 and 4, the participants detected a peripheral target that was also isoluminant with the background. Under these conditions, it was found that both luminance and isoluminance cues captured attention. The results are discussed in terms of the roles of the dorsal and ventral streams in visual orienting, and it is concluded that our findings provide partial support for the contingent involuntary orienting hypothesis of C. Folk and colleagues.