S-ketamine influences strategic allocation of attention but not exogenous capture of attention.

We investigated whether s-ketamine differentially affects strategic allocation of attention. In Experiment 1, (1) a less visible cue was weakly masked by the onsets of competing placeholders or (2) a better visible cue was not masked because it was presented in isolation. Both types of cue appeared more often opposite of the target (75%) than at target position (25%). With this setup, we tested for strategic attention shifts to the opposite side of the cues and for exogenous attentional capture toward the cue's side in a short cue-target interval, as well as for (reverse) cueing effects in a long cue-target interval after s-ketamine and after placebo treatment in a double-blind within-participant design. We found reduced strategic attention shifts after cues presented without placeholders for the s-ketamine compared to the placebo treatment in the short interval, indicating an early effect on the strategic allocation of attention. No differences between the two treatments were found for exogenous attentional capture by less visible cues, suggesting that s-ketamine does not affect exogenous attentional capture in the presence of competing distractors. Experiment 2 confirmed that the competing onsets of the placeholders prevented the strategic cueing effect. Taken together, the results indicate that s-ketamine affects strategic attentional capture, but not exogenous attentional capture. The findings point to a more prominent role of s-ketamine during top-down controlled forms of attention that require suppression of automatic capture than during automatic capture itself.

No conflict control in the absence of awareness.

INTRODUCTION: In the present study we tested whether control over the impact of potentially conflicting information depends on awareness of that conflicting information. METHOD AND RESULTS: In Experiment 1 participants performed a response-priming task, with either masked or unmasked primes. Prime awareness was assessed on a trial-by-trial basis. A typical conflict control pattern, with reduced priming effects following incongruent rather than congruent primes in the preceding trial was found. Yet, this pattern was obtained only when the prime information was visible and not when it was invisible. With invisible primes the effect did not occur, even when participants accidently judged the prime information correctly. Importantly, this confinement of the conflict adaptation effect to unmasked primes occurred despite identical prime processing times with and without masking-a variable that was confounded with prime awareness in previous studies. In Experiment 2, a similar data pattern was found for judgment times regarding the congruency of prime-target pairs. CONCLUSION: Altogether, the results support the conclusion that awareness of visual primes is important for controlling conflict in visuo-motor processing.

Stimulus-driven attentional capture by subliminal onset cues.

In two experiments, we tested whether subliminal abrupt onset cues capture attention in a stimulus-driven way. An onset cue was presented 16 ms prior to the stimulus display that consisted of clearly visible color targets. The onset cue was presented either at the same side as the target (the valid cue condition) or on the opposite side of the target (the invalid cue condition). Because the onset cue was presented 16 ms before other placeholders were presented, the cue was subliminal to the participant. To ensure that this subliminal cue captured attention in a stimulus-driven way, the cue's features did not match the top-down attentional control settings of the participants: (1) The color of the cue was always different than the color of the non-singleton targets ensuring that a top-down set for a specific color or for a singleton would not match the cue, and (2) colored targets and distractors had the same objective luminance (measured by the colorimeter) and subjective lightness (measured by flicker photometry), preventing a match between the top-down set for target and cue contrast. Even though a match between the cues and top-down settings was prevented, in both experiments, the cues captured attention, with faster response times in valid than invalid cue conditions (Experiments 1 and 2) and faster response times in valid than the neutral conditions (Experiment 2). The results support the conclusion that subliminal cues capture attention in a stimulus-driven way.

Oculomotor capture by supraliminal and subliminal onset singletons: the role of contrast polarity.

According to a top-down explanation of subliminal oculomotor capture, only subliminal distractors with a contrast polarity matching that of the searched-for targets should capture attention. For instance, when looking for white targets only subliminal white but not black distractors should capture attention. In contrast, according to a bottom-up explanation of such capture effects, subliminal distractors with a contrast polarity different to that of the searched-for targets should also capture attention. For instance, even when looking for white targets, subliminal black distractors should capture attention. Here, we used subliminal singleton-onset distractors in the same vertical hemifield as the target versus singleton-onset distractors in the opposite vertical field to the target, and tested whether oculomotor capture by these distractors depended on a match between the searched-for target contrasts and the distractor contrasts, by measuring saccade latency, saccade trajectory deviation, and saccade endpoint deviation. We found evidence for oculomotor capture: subliminal distractors in the opposite field delayed saccade execution towards the target. This delay was found in comparison to subliminal distractors in the same hemifield as the target. In line with a bottom-up explanation, this delay was independent of the similarity between the distractor contrast polarity and the searched-for target contrast polarity. Together with the subliminality of the distractors, the experiment confirmed bottom-up oculomotor capture by subliminal singleton-onsets.

Exogenous attentional capture by subliminal abrupt-onset cues: evidence from contrast-polarity independent cueing effects.

In the present study, we tested whether subliminal abrupt-onset cues capture attention in a bottom-up or top-down controlled manner. For our tests, we varied the searched-for target-contrast polarity (i.e., dark or light targets against a gray background) over four experiments. In line with the bottom-up hypothesis, our results indicate that subliminal-onset cues capture attention independently of the searched-for target-contrast polarity (Experiment 1), and this effect is not stronger for targets that matched the searched-for target-contrast polarity (Experiment 2). In fact, even to-be-ignored cues associated with a no-go response captured attention in a salience-driven way (Experiment 3). For supraliminal cues, we found attentional capture only by cues with a matching contrast polarity, reflecting contingent capture (Experiment 4). The results point toward a specific role of subliminal abrupt onsets for attentional capture.

Parafoveal X-masks interfere with foveal word recognition: evidence from fixation-related brain potentials.

The boundary paradigm, in combination with parafoveal masks, is the main technique for studying parafoveal preprocessing during reading. The rationale is that the masks (e.g., strings of X's) prevent parafoveal preprocessing, but do not interfere with foveal processing. A recent study, however, raised doubts about the neutrality of parafoveal masks. In the present study, we explored this issue by means of fixation-related brain potentials (FRPs). Two FRP conditions presented rows of five words. The task of the participant was to judge whether the final word of a list was a "new" word, or whether it was a repeated (i.e., "old") word. The critical manipulation was that the final word was X-masked during parafoveal preview in one condition, whereas another condition presented a valid preview of the word. In two additional event-related brain potential (ERP) conditions, the words were presented serially with no parafoveal preview available; in one of the conditions with a fixed timing, in the other word presentation was self-paced by the participants. Expectedly, the valid-preview FRP condition elicited the shortest processing times. Processing times did not differ between the two ERP conditions indicating that "cognitive readiness" during self-paced processing can be ruled out as an alternative explanation for differences in processing times between the ERP and the FRP conditions. The longest processing times were found in the X-mask FRP condition indicating that parafoveal X-masks interfere with foveal word recognition.

Inhibition of return is no hallmark of exogenous capture by unconscious cues.

Inhibition of irrelevant information and response tendencies is a central characteristic of conscious control and executive functions. However, recent theories in vision considered Inhibition of Return (IOR: slower responses to attended than unattended positions) to be a hallmark of automatic exogenous capture of visual attention by unconscious cues. In the present study, we show that an unconscious cue that exogenously captures attention does not lead to IOR. First of all, subliminal cues with a contrast different from a searched-for target contrast capture attention independently of their match of contrast polarity to the search criteria. This is found with a short cue-target interval (Exp. 1). However, the same cues do not lead to IOR with a long cue-target interval. The lack of IOR is also verified for several intermediate intervals (Exp. 2), for high-contrast cues and low-contrast targets (Exp. 3), and with lower luminance cues presented on a CRT screen (Exp. 4). Finally, no capture effect but IOR is found for consciously perceived anti-predictive cues (Exp. 5). Together the results support the notion of a double dissociation between IOR and exogenous capture and are in line with a decisive role of consciousness for inhibition.

Unconscious Cueing via the Superior Colliculi: Evidence from Searching for Onset and Color Targets.

According to the bottom-up theory of attention, unconscious abrupt onsets are highly salient and capture attention via the Superior Colliculi (SC). Crucially, abrupt onsets increase the perceived contrast. In line with the SC hypothesis, unconscious abrupt-onset cues capture attention regardless of the cue color when participants search for abrupt-onset targets (Experiment 1). Also, stronger cueing effects occur for higher than lower contrast cues (Experiment 2) and for temporally, rather than nasally, presented stimuli (Experiment 3). However, in line with the known color-insensitivity of the SC, the SC pathway is shunted and unconscious abrupt-onset cues no longer capture attention when the participants have to search for color-defined targets (Experiment 4) or color-singleton targets (Experiment 5). When using color change cues instead of abrupt-onset cues, the cueing effect also vanishes (Experiment 6). Together the results support the assumption that unconscious cues can capture attention in different ways, depending on the exact task of the participants, but that one way is attentional capture via the SC. The present findings also offer a reconciliation of conflicting results in the domain of unconscious attention.

When attractiveness demands longer looks: the effects of situation and gender.

We investigated how aesthetics guides our exploration of the environment. We embedded attractive and nonattractive faces into complex, real-world scenes and measured eye movements during scene viewing. We examined whether attractive faces would elicit longer looks, which would suggest that the aesthetic response orients people toward the rewarding and pleasing aspects of the environment. Experiment 1 showed that mean fixation, mean first fixation, and total fixation durations were longer to attractive faces, and fixations were longest to female faces and by female perceivers. In Experiment 2, we examined whether these effects of attractiveness are sensitive to situational factors. When perceivers were subjected to a threat or social approach manipulation prior to viewing the scenes, we confirmed specific hypotheses concerning the two manipulations. In accordance with the hypothesis that males have higher aggression potential than females, there were no differences in fixation durations between attractive and nonattractive male faces in the threat condition. On the other hand, in the social approach condition, both female and male attractive faces received longer looks. These results suggest that the aesthetic response orients people not only to the pleasing aspects of their environment, but also to those features that are adaptively relevant.