Masked partial priming of letter perception

In three experiments testing 178 subjects, letter targets were preceded by briefly presented, pattern-masked primes formed by deleting pixels in a larger or smaller version of the target stimulus. In Experiment 1A (alphabetic decision)and Experiment 1B (letter naming) a slight advantage was observed for global primes (alternate pixels deleted) compared with junction primes (midsegment information removed). This advantage was stronger at 50 ms prime exposures than at 30 ms exposures in the naming task. In Experiment 2 (letter naming), midsegment primes (with junction information removed) produced faster latencies than did junction primes. This result was replicated in a third experiment and was shown to be independent of target letter case and the relative size of prime and target stimuli. The same midsegment and junction primes did not facilitate performance compared to neutral primes in the alphabetic decision task. These results suggest that masked partial priming of letter naming can be usefully applied to the study of basic processes in letter perception.     

A new form of human spatial attention: Automated symbolic orienting

The control of human attention is typically conceptualized either in terms of exogenous automatic processes that are driven by external sensory stimulation or endogenous strategic processes that are driven by internal expectancies about events in the environment. However, this classic dichotomy has struggled to explain a wealth of new data demonstrating that behaviourally and biologically relevant visual stimuli, like arrow and eye direction, elicit shifts of spatial attention that on the one hand, appear exogenous, and on the other hand, endogenous. To address this issue, we used a double-cueing task that combined arrows with classic cues known to invoke either exogenous or endogenous orienting. Our data suggest that behaviourally relevant directional cues, like arrows, engage a new form of cortically mediated orienting—automated symbolic orienting—that operates independent of, and in parallel with, the two classic forms of exogenous and endogenous spatial attention.     

Visual target detection is impaired at event boundaries

Boundaries between meaningful events are key moments in comprehending human action. At these points, viewers may focus on the event's contents at the expense of other information. We tested whether visual detection was impaired at those moments perceivers judged to be boundaries between events. Short animated football clips were used as stimulus material, and event boundaries were imposed by having the ball change possession. In a first experiment, we found that possession changes were perceived to be event boundaries. In a second experiment, participants were asked to keep track of 4 of 10 players and to watch for 120 ms probes appearing either at an event boundary or a nonboundary. Probe detection was less accurate at event boundaries. This result suggests that the segmentation of ongoing activity into events corresponds with the regulation of attention over time.     

The role of prior exposure in the capture of attention by items in working memory

The Biased Competition Model (BCM) suggests both top-down and bottom-up biases operate on selective attention (e.g., Desimone & Duncan, 1995). It has been suggested that top-down control signals may arise from working memory. In support, Downing (2000) found faster responses to probes presented in the location of stimuli held vs. not held in working memory. Soto, Heinke, Humphreys, and Blanco (2005) showed the involuntary nature of this effect and that shared features between stimuli were sufficient to attract attention. Here we show that stimuli held in working memory had an influence on the deployment of attentional resources even when: (1) It was detrimental to the task, (2) there was equal prior exposure, and (3) there was no bottom-up priming. These results provide further support for involuntary top-down guidance of attention from working memory and the basic tenets of the BCM, but further discredit the notion that bottom-up priming is necessary for the effect to occur.     

Look who's talking? Sound changes gaze behaviour in a dynamic social scene

Humans often look at other people in natural scenes, and previous research has shown that these looks follow the conversation and that they are sensitive to sound in audiovisual speech perception. In the present experiment, participants viewed video clips of four people involved in a discussion. By removing the sound, we asked whether auditory information would affect when speakers were fixated, how fixations between different observers were synchronized, and whether the eyes or mouth were looked at most often. The results showed that sound changed the timing of looks—by alerting observers to changes in conversation and attracting attention to the speaker. Clips with sound also led to greater attentional synchrony, with more observers fixating the same regions at the same time. However, looks towards the eyes of the people continued to dominate and were unaffected by removing the sound. These findings provide a rich example of multimodal social attention.     

No difference in flanker effects for sad and happy schematic faces: A parametric study of temporal parameters

Flanker effects with schematic faces have been reported to be larger for happy than for sad faces, allegedly because sad faces restrict the focus of spatial attention. We report a parametric study that fails to replicate this effect. Participants performed speeded identifications of happy or sad faces accompanied by compatible or incompatible flanker faces. We varied the temporal interval between presentation of central target and flanker faces because differential attentional effects of happy and sad faces should critically depend on this variable. In contradiction to the literature, we found large compatibility effects that were modulated by temporal parameters, but not by the emotional valence of the faces, and not in the way consistent with differential attentional modulation. We conclude that previously reported asymmetries in flanker tasks with schematic faces are not due to changes in attentional scope (mediated by emotion or otherwise), but rather to perceptual low-level differences.     

Contextual cueing in multiple object tracking

In this study, we examined whether visual context can be learned through a dynamic display and whether it can facilitate sustained attentional tracking by combining a multiple object tracking (MOT) task and a contextual cueing procedure. The trajectories of the targets and distractors in the MOT task were made invariant by repeatedly presenting them. The results revealed that when the targets were repeatedly displayed, tracking performance implicitly improved, and this effect was enhanced when the unattended distractors in the displays were also repeated. However, the repetition of the distractors alone did not produce any effect. Interestingly, when the targets and distractors were switched in a display in which the distractors had been previously repeated, the tracking performance was impaired as compared with that in the case of nonrepeated displays. We concluded that the contextual information in a dynamic display facilitates attentional tracking and that different types of contextual modulations occurred in MOT processes, such as facilitation for attended targets and inhibition for ignored distractors.     

Attentional capture by singletons is contingent on top-down control settings: Evidence from electrophysiological measures

The present study examined whether the capture of spatial attention is driven by stimulus salience (e.g., object uniqueness) or by a match to current attentional control settings (contingent capture). We measured the N2pc effect, a component of the event-related brain potential thought to reflect lateralized attentional allocation. On every trial, a noninformative cue display containing a colour singleton box was followed by a target display of letters. Participants searched for a target letter in a specified colour (in Experiments 1–3) or within a specified shape (in Experiment 4) while ignoring other stimuli. The key manipulation was whether the singleton cue contained the target-defining feature (e.g., a specific colour). Experiment 1 revealed signs of attention capture—a cue validity effect and an N2pc effect—only for singleton cues that contained the target-defining feature. This pattern persisted even when we increased the salience of the singleton box (Experiments 2 and 3). Irrelevant colour singletons also failed to produce a significant N2pc effect when the target was defined based on shape rather than colour (Experiment 4). We conclude that attention capture is strongly contingent on top-down attentional control settings, not bottom-up stimulus salience.     

What makes an angry face look so … angry? Examining visual attention to the shape of threat in children and adults

Threatening facial expressions like anger can signal potential danger. Past research has established that both adults and children have an attentional bias for angry faces, visually detecting their presence more quickly than happy or neutral faces. More recent research has suggested that specific features of angry faces (such as the downward-pointing “V” shaped brow) are the effective stimulus in their rapid detection. However, research examining this issue has only been done with adults. In the current research, we examine the detection of the features of the downward-pointing “V” in both adults and preschool children using a touchscreen visual search procedure. In two experiments, both adults and children detected the downward-pointing “V” more quickly than an upward-pointing “V”. As the first evidence that young children exhibit the same superior detection of the features of threatening facial expressions that adults do, this research provides important support for the existence of an evolved attentional bias for threatening stimuli.