Below you can find papers currently published along with their PDF files for download. For those under review or in preparation, please see my C.V. from the navigation above!

On preventing capture: Does greater salience cause greater suppression?

It has been proposed that salient objects have high potential to disrupt target performance, and so people learn to proactively suppress them, thereby preventing these salient distractors from capturing attention in the future. Consistent with this hypothesis, Gaspar et al. (Proceedings of the National Academy of Sciences, 113(13), 3693–3698, 2016) reported that the PD (believed to index suppression) was larger for high-salient color distractors than for low-salient color distractors. The present study looked for converging evidence that salience triggers suppression using established behavior measures of suppression. Following Gaspar et al., our participants searched for a yellow target circle among nine background circles, which sometimes included one circle with a unique color. The distractor was either high or low in salience with respect to the background circles. The question was whether the high-salient color would be proactively suppressed more strongly than the low-salient color. This was assessed using the capture-probe paradigm. On 33% of trials, probe letters appeared inside colored circles and participants were to report those letters. If high-salient colors are more strongly suppressed, then probe recall accuracy should be lower at locations with the high-salient color than those with the low-salient color. Experiment 1 found no such efect. A similar fnding was observed in Experiment 2 after addressing possible foor efects. These fndings suggest that proactive suppression is not caused by salience. We propose that the PD refects not only proactive suppression but also reactive suppression.

Do salient abrupt onsets trigger suppression?

Many studies have indicated that abrupt onsets can capture our attention involuntarily. The present study examined whether task-irrelevant onsets trigger strong suppression of their features, to reduce the ability of the onsets to capture attention. We used a capture-probe paradigm with salient abrupt onsets as precues. Participants performed a search task (70% of the trials) with occasional probe tasks mixed in (30% of the trials). In Experiment 1, two irrelevant-color distractors appeared simultaneously with the target, one of which was always precued by the abrupt onset. The question was whether an abrupt onset cue would promote suppression of the correlated color, thereby impeding recall of probe letters at a location with that color. This did not happen. The same result was obtained in Experiment 2, despite removing the target shape from the probe display to minimize floor effects and despite presenting only one distractor color per trial to further strengthen the onset-color association. In Experiment 3, one of the two irrelevant-color distractors abruptly onsetted 50 ms before the other search elements. Despite efforts to promote suppression of the cued distractor color, probe recall accuracy was again similar for the cued and non-cued distractor colors. We conclude that distractor features are suppressed but that making them especially salient does not noticeably enhance this suppression. The suppression mechanism is therefore geared towards helping observers discriminate between target features and distractor features, not towards beating down the most threatening object. 

The role of visual working memory capacity in attention capture among video game players

It is well established that attention can be captured by salient distractors. Some studies have found that action video game players were less susceptible to attention capture by irrelevant distractors than non-players. Other studies have also found that individuals with greater visual working memory capacity are less susceptible to capture by irrelevant distractors than individuals with lower visual working memory capacity. The present study examined whether action video game players were less susceptible to be captured by salient distractors and, if so, whether that relationship was due to greater visual working memory capacity. Participants completed a questionnaire reporting their video game playing experience, followed by a color change detection task assessing their visual working memory capacity. They then performed an attention capture task, where they determined the orientation of a bar within a shape singleton while attempting to ignore a color singleton distractor that appeared in 50% of the trials. Results showed that action video game players did not produce less capture effect than nonaction video game players. However, high visual working memory capacity individuals produced less capture effect than low visual working memory capacity individuals regardless of their video game experience. These results suggest that the ability to resist capture by irrelevant distractors may be better explained by individual differences in visual working memory capacity than by action video game experience.

On preventing attention capture: Is singleton suppression actually singleton suppression?

It is commonly assumed that salient singletons generate an “attend-to-me signal” which causes suppression to develop over time, eventually preventing capture. Despite this assumption and the name “singleton suppression,” a causal link between salience and suppression has not yet been clearly established. We point out the plausibility of a simple alternative mechanism: distractors might be suppressed because they are distractors rather than targets, even when non-salient. To look for evidence of salience-based suppression, we had participants search for a target shape among distractors, which sometimes included irrelevant-colored distractors. The critical manipulation was whether the irrelevant-colored distractor was salient (a color singleton) or non-salient (three non-target colored shapes; a triplet). On 30% of trials, probe letters were presented briefly inside each shape and participants were to report those letters. Probe recall below baseline indicates suppression. Experiment 1 showed that suppression was not triggered any more strongly by salient distractors (singletons) than by non-salient distractors (triplets). Experiment 2 showed that strong suppression effects developed rapidly even in the absence of salient singletons. These findings raise the thus far neglected question of whether salience plays any role in suppression.

What do we know about suppression of attention capture?

Luck et al. [(2021). Progress toward resolving the attentional capture debate. Visual Cognition, 29(1), 1–21.] proposed singleton suppression as a promising resolution to the attention capture debate. Specifically, salient singletons are assumed to generate an “attend-to-me” signal and therefore represent a threat that triggers suppression. One noteworthy limitation is that singleton suppression has been demonstrated only when the singleton has a colour or location that is consistently associated with being a distractor. This raises the important question of whether “singleton” suppression has anything to do with being a singleton. Drawing on our recent work, we propose the alternative view that suppression occurs for colours associated with being distractors, regardless of whether they are also salient.

Password Entry Times for Recognition-based Graphical Passwords

Graphical passwords offer a more memorable alternative to traditional, text-based passwords. Among current contenders, cued-recall based click-point or gesture centered authentication systems like Microsoft’s picture gesture authentication (PGA) have been commercially more successful than recognition based systems (e.g., PassFaces). One perceived drawback of graphical authentication systems in general and especially recognition based authentication is the assumption that graphical authentication is slower and thus less user-friendly than traditional password entry via keyboard. This paper addresses these concerns and demonstrates a lower limit for recognition-based password entry times achievable with sufficient practice. While slightly slower than traditional keyboard based passwords, the entry speed of often-used graphical passwords is shown to reach 10 bits/s in an optimized configuration, which is sufficient for everyday use (3-6s per authentication sequence @ 36 bits) and exceeds the reported speed of similarly secure text-based passwords on non-traditional devices using virtual keyboards.

Can VoiceScapes Assist in Menu Navigation? 

Providing better information access to blind users is an important goal in the context of accessible interface design. Similarly, designers of user interfaces benefit from alternative interface techniques for usage scenarios in which visual (graphical) interfaces are either not possible or suboptimal. In our study we compared a traditional serial aural presentation of menu items to a new simultaneous aural presentation of up to seven menu items. These continuously present VoiceScapes allow the user to actively scan the auditory display to find the most appropriate command. While VoiceScapes are more difficult and attentionally more demanding than other formats of presentation, extended use might allow experienced users to more efficiently navigate complex menu hierarchies. A first pilot experiment with 13 sighted participants presented here tested the basic viability of this approach.