Elisabeth Blagrove

No difference between conscious and nonconscious visuomotor control: Evidence from perceptual learning in the masked prime task ☆

Negative compatibility effects (NCEs) in the masked-prime paradigm are usually obtained when primes are masked effectively. With ineffective masks-and primes above the perceptual threshold-positive compatibility effects (PCEs) occur. We investigated whether this pattern reflects a causal relationship between conscious awareness and low-level motor control, or whether it reflects the fact that both are affected in the same way by changes in physical stimulus attributes. In a 5-session perceptual learning task, participants learned to consciously identify masked primes. However, they showed unaltered NCEs that were not different from those produced by participants in a control group without equivalent perceptual learning. A control experiment demonstrated that no NCEs occur when prime identification is made possible by ineffective masking. The results suggest that perceptual awareness and low-level motor control are affected by the same factors, but are fundamentally independent of each other.

Negative triangles: Simple geometric shapes convey emotional valence.

It has been suggested that downward pointing triangles convey negative valence, perhaps because they mimic an underlying primitive feature present in negative facial expressions (Larson, Aronoff, and Stearns, 2007). Here, we test this proposition using a flanker interference paradigm in which participants indicated the valence of a central face target, presented between two adjacent distracters. Experiment 1 showed that, compared with face flankers, downward pointing triangles had little influence on responses to face targets. However, in Experiment 2, when attentional competition was increased between target and flankers, downward pointing triangles slowed responses to positively valenced face targets, and speeded them to negatively valenced targets, consistent with valence-based flanker compatibility effects. These findings provide converging evidence that simple geometric shapes may convey emotional valence.

Visual marking and facial affect: Can an emotional face be ignored?

Previewing a set of distractors allows them to be ignored in a subsequent visual search task (Watson & Humphreys, 1997). Seven experiments investigated whether this preview benefit can be obtained with emotional faces, and whether negative and positive facial expressions differ in the extent to which they can be ignored. Experiments 1-5 examined the preview benefit with neutral, negative, and positive previewed faces. These results showed that a partial preview benefit occurs with face stimuli, but that the valence of the previewed faces has little impact. Experiments 6 and 7 examined the time course of the preview benefit with valenced faces. These showed that negative faces were more difficult to ignore than positive faces, but only at short preview durations. Furthermore, a full preview benefit was not obtained with face stimuli even when the preview duration was extended up to 3 s. The findings are discussed in terms of the processes underlying the preview benefit, their ecological sensitivity, and the role of emotional valence in attentional capture and guidance.

Incidental learning of S-R contingencies in the masked prime task.

Subliminal motor priming effects in the masked prime paradigm can only be obtained when primes are part of the task set. In 2 experiments, the authors investigated whether the relevant task set feature needs to be explicitly instructed or could be extracted automatically in an incidental learning paradigm. Primes and targets were symmetrical arrows, with target color, not shape, the response-relevant feature. Shape and color covaried for targets (e.g., <> always blue, >< always green), whereas primes were always black. Over time, a negative compatibility effect (NCE; response benefits when prime and target had different shapes) developed, indicating that primes affected the motor system. When target shape and color varied independently (control condition), no NCE occurred, in line with the assumption that the NCE reflects task set-dependent motor processes, not perceptual interactions.

Ignoring real faces: Effects of valence, threat, and salience

Facial stimuli have been shown to accrue a special status within visual processing, particularly when attention is prioritized to one face over another on the basis of affective content. This has been examined in relation to the ability of faces to guide or hold attention, or to resist attentional suppression. Previous work has shown that schematic faces can only be partially ignored and that the emotional valence of to-be-ignored faces has little effect. Given recent debates concerning the use of schematic faces, here we examined the ease with which photorealistic faces could be ignored. Although we found evidence of a partial preview benefit for these stimuli, the findings were complex, with stimulus salience, valence, and threat content interacting to affect both the strength of the benefit and target detection efficiency (Exps. 1–3). Experiment 4 then clarified the effects of physical salience and perceived stimulus similarity in the previous experiments, demonstrating that a combination of these factors is likely to account for the search patterns observed.

Inhibition in time-based visual selection: Strategic or by default?

The visual marking mechanism (Watson & Humphreys, 1997) allows new objects to be prioritized by applying top-down inhibition to a set of previewed distractors, increasing the efficiency of future visual search. However, if this inhibition results in little or no search facilitation, do people continue to apply it or do they strategically withhold it? Here we present 6 experiments in which we examined how participants control this inhibitory mechanism. Experiments 1 to 3 showed that in difficult search contexts, participants did not modulate the extent to which they applied inhibition based on the proportion of trials in which inhibition would have been useful. This was the case, even when explicitly cued before each trial as to the utility of applying inhibition (Experiment 4). In contrast, when search was conducted in predominantly easy search contexts, there was some evidence that inhibition was applied strategically (Experiments 5 and 6); however, the extent of this control was relatively modest. The findings are discussed in terms of the mechanisms of top-down attentional control and implications for failures of attention in real-world contexts.

Tagging multiple emotional stimuli: negative valence has little benefit.

Six experiments examined the influence of emotional valence on the tagging and enumeration of multiple targets. Experiments 1, 5 and 6 found that there was no difference in the efficiency of tagging/enumerating multiple negative or positive stimuli. Experiment 2 showed that, when neutral-expression face distractors were present, enumerating negative targets was faster overall, but was only more efficient for small numbers of targets. Experiments 3 and 4 determined that this negative target advantage was most likely caused by increased attentional guidance to negatively-valenced stimuli and was not based on simple visual feature differences. The findings suggest that a multiple-target negative stimulus advantage will only occur under conditions of attentional competition, and for relatively small numbers of targets. The results are discussed in relation to theories of multiple- and single-item processing, threat-priority mechanisms, and the types of representations that support different attentional tasks.

Look on the bright side : positivity bias modulates interference effects in the Simon Task

Negative faces are detected more quickly but categorized more slowly than positive faces. Using a Simon task, we examined stimulus- and response-related processes of this dissociation: If negative stimuli are both processed and responded to more quickly than positive ones, they should elicit reduced Simon effects. Conversely, if negative stimuli are processed more quickly but responded to more slowly, enlarged Simon effects should occur. Consistent with the first possibility, negative stimuli showed reduced Simon effects. Unexpectedly, this reduction transferred to neutral stimuli (arrows and pointing hands) requiring the same response as negative faces. This pattern suggests that spatial attention became biased toward the side associated with a positive-face response and away from the side associated with a negative-face response, demonstrating that, similar to higher level cognitive decision processes, even early attentional processes can be subject to a positivity bias (“Pollyanna effect”).