Challenging the similarity rule of visual crowding: When detrimental clutter becomes beneficial uniformity

In real life, objects are seldomly encountered in isolation but are more often than not surrounded by other items. Context has been shown to strongly modulate whether and how objects are perceived. In visual crowding, nearby items (‘flankers’) prevent the accurate perception of a target object. One of the central crowding rules concerns its dependence on target-flanker similarity, with usually weak crowding when target and flankers differ on a given feature. For instance, the similarity rule predicts the ‘polarity advantage’: the superior identification of a crowded target when flanked by opposite rather than same contrast polarity items. The usual benefit of low target-flanker similarity is well explained by grouping: when the target is easily segmented from its flankers, such weak target-flanker grouping typically yields mild crowding. Here, in three studies, I demonstrate strong limitations to the generality of the similarity rule. In the first study, it was revealed that the usual benefit of low target-flanker similarity did not transfer to peripheral word recognition. In particular, word recognition deteriorated when word parts – either syllables or non-syllables - alternated in contrast polarity compared to words consisting of all same contrast polarity parts. In the second study, the similarity rule –typically shown with regard to a single crowded target – was reversed when multiple crowded targets were task-relevant. When neighboring trigram letters had the same versus opposite contrast polarity, performance was worse when reporting the central letter only but surprisingly superior when reporting all letters. In the third study, I show that interactions between two features - contrast polarity and orientation – can break the similarity rule of crowding. When discriminating the central line tilt within a line triplet, the usual advantage of opposite compared to same contrast polarity flankers (relative to the target) depended on flanker orientations. The polarity advantage was found with upright (||) and bidirectional (\/ or /\) flankers, but was absent with unidirectional flankers (\\ or //). Taken together, the current findings strongly challenge the generality of the similarity rule. I propose that attentional and configural factors can overcome the usual cost of strong grouping of target and flankers, revealing benefits of stimulus uniformity instead

Multidimensional feature interactions in visual crowding: When configural cues eliminate the polarity advantage.

Crowding occurs when surrounding objects (flankers) impair target perception. A key property of crowding is the weaker interference when target and flankers strongly differ on a given dimension. For instance, identification of a target letter is usually superior with flankers of opposite versus the same contrast polarity as the target (the "polarity advantage"). High performance when target-flanker similarity is low has been attributed to the ungrouping of target and flankers. Here, we show that configural cues can override the usual advantage of low target-flanker similarity, and strong target-flanker grouping can reduce - instead of exacerbate - crowding. In Experiment 1, observers were presented with line triplets in the periphery and reported the tilt (left or right) of the central line. Target and flankers had the same (uniform condition) or opposite contrast polarity (alternating condition). Flanker configurations were either upright (||), unidirectionally tilted (\\ or //), or bidirectionally tilted (\/ or /\). Upright flankers yielded stronger crowding than unidirectional flankers, and weaker crowding than bidirectional flankers. Importantly, our results revealed a clear interaction between contrast polarity and flanker configuration. Triplets with upright and bidirectional flankers, but not unidirectional flankers, showed the polarity advantage. In Experiments 2 and 3, we showed that emergent features and redundancy masking (i.e. the reduction of the number of perceived items in repeating configurations) made it easier to discriminate between uniform triplets when flanker tilts were unidirectional (but not when bidirectional). We propose that the spatial configurations of uniform triplets with unidirectional flankers provided sufficient task-relevant information to enable a similar performance as with alternating triplets: strong-target flanker grouping alleviated crowding. We suggest that features which modulate crowding strength can interact non-additively, limiting the validity of typical crowding rules to contexts where only single, independent dimensions determine the effects of target-flanker similarity

Ready for the Worst? Negative Affect in Anticipation of a Stressor Does Not Protect Against Affective Reactivity.

Lay wisdom suggests feeling negative while awaiting an upcoming stressor - anticipatory negative affect - shields against the blow of the subsequent stressor. However, evidence is mixed, with different lines of research and theory indirectly suggesting that anticipatory negative affect is helpful, harmful, or has no effect on emotional outcomes. In two studies, we aimed to reconcile these competing views by examining the affective trajectory across hours, days, and months, separating affective reactivity and recovery. In Study 1, first-year students (N=101) completed 9 days of experience sampling (10 surveys/day) as they received their first-semester exam grades, and a follow-up survey 5 months later. In Study 2, participants (N=73) completed 2 days of experience sampling (60 surveys/day) before and after a Trier Social Stress Test. We investigated the association between anticipatory negative affect and the subsequent affective trajectory, investigating (1) reactivity immediately after the stressor, (2) recovery across hours (Study 2) and days (Study 1), and (3) recovery after 5 months (Study 1). Across the two studies, feeling more negative in anticipation of a stressor was either associated with increased negative affective reactivity, or unassociated with affective outcomes. These results run counter to the idea that being affectively ready for the worst has psychological benefits, suggesting that instead, anticipatory negative affect can come with affective costs

Disrupting uniformity: Feature contrasts that reduce crowding interfere with peripheral word recognition

Peripheral word recognition is impaired by crowding, the harmful influence of surrounding objects (flankers) on target identification. Crowding is usually weaker when the target and the flankers differ (for example in color). Here, we investigated whether reducing crowding at syllable boundaries improved peripheral word recognition. In Experiment 1, a target letter was flanked by single letters to the left and right and presented at 8° in the lower visual field. Target and flankers were either the same or different in regard to contrast polarity, color, luminance, and combined color/luminance. Crowding was reduced when the target differed from the flankers in contrast polarity, but not in any of the other conditions. Using the same color and luminance values as in Experiment 1, we measured recognition performance (speed and accuracy) for uniform (e.g., all letters black), congruent (e.g., alternating black and white syllables), and incongruent (e.g., alternating black and white non-syllables) words in Experiment 2. Participants verbally reported the target word, briefly displayed at 8° in the lower visual field. Congruent and incongruent words were recognized slower compared to uniform words in the opposite contrast polarity condition, but not in the other conditions. Our results show that the same feature contrast between the target and the flankers that yielded reduced crowding, deteriorated peripheral word recognition when applied to syllables and non-syllabic word parts. We suggest that a potential advantage of reduced crowding at syllable boundaries in word recognition is counteracted by the disruption of word uniformity

Inoculation history affects community composition in experimental freshwater bacterioplankton communities

Priority effects occur when the arrival order of species or genotypes has a lasting effect on community or population structure. For freshwater bacteria, priority effects have been shown experimentally among individual species, but no experiments have been performed using complex natural communities. We investigated experimentally whether a foreign bacterioplankton community influences the community assembly trajectory when inoculated prior to the local community, whether inoculation time lag affects priority effects, and how the individual OTUs responded to time lag. Two bacterioplankton communities from dissimilar ponds were inoculated into one of the natural media with a time lag of 0, 12, 36 or 60 hours, giving advantage in time to the foreign community. All three time lags resulted in priority effects, as the final community composition of these treatments differed significantly from that of the treatment with no time lag, but compositional shifts were not linear to inoculation time lag. The responses of individual OTUs to time lag were highly diverse and not predictable based on their immigration history or relative abundance in the inocula or control. The observed impact and complexity of priority effects in multi-species systems emphasize the importance of this process in structuring both natural and industrial bacterial communities.status: publishe

Zinc tolerance of the soil nitrifying community occurs in copper contaminated soils: illustrations of co-tolerance

Adaptation of soil microorganisms to trace metals has frequently been shown, and is often associated with a changed community structure. We previously showed that Zn tolerance developed in Zn spiked soils and Cu tolerance in Cu spiked soils. It is unclear whether the effects of long-term trace metal exposure on i) metal tolerance and on ii) the microbial community structure are site and metal specific. However, the development of co-tolerance for Zn and Cu has been observed previously, but was not yet shown for the soil nitrifying community. We speculate that co-tolerance is associated with similar shifts in community structure. Therefore, the extent of Zn tolerance and the nitrifying community composition were assessed in artificially Zn and Cu contaminated soil samples from two different sites (Zeveren (Belgium) and Spalding (Australia)). Copper spiking induced the development of Zn tolerance in the Spalding soil. The amoA community composition of the Cu spiked Spalding soil resembled that of the Zn spiked Spalding soil. However, the amoA community of the copper spiked Zeveren soil, which was not Zn tolerant, showed a distinct composition compared to the zinc spiked Zeveren soil. Co-tolerance is demonstrated here, but the community shifts are not necessarily identical upon either Cu or Zn exposure.status: publishe

Ready for the Worst? Negative Affect in Anticipation of a Stressor Does Not Protect Against Affective Reactivity

Lay wisdom suggests feeling negative while awaiting an upcoming stressor – anticipatory negative affect – shields against the blow of the subsequent stressor. However, evidence is mixed, with different lines of research and theory indirectly suggesting that anticipatory negative affect is helpful, harmful, or has no effect on emotional outcomes. In two studies, we aimed to reconcile these competing views by examining the affective trajectory across hours, days, and months, separating affective reactivity and recovery. In Study 1, first-year students (N=101) completed 9 days of experience sampling (10 surveys/day) as they received their first-semester exam grades, and a follow-up survey 5 months later. In Study 2, participants (N=73) completed 2 days of experience sampling (60 surveys/day) before and after a Trier Social Stress Test. We investigated the association between anticipatory negative affect and the subsequent affective trajectory, investigating (1) reactivity immediately after the stressor, (2) recovery across hours (Study 2) and days (Study 1), and (3) recovery after 5 months (Study 1). Across the two studies, feeling more negative in anticipation of a stressor was either associated with increased negative affective reactivity, or unassociated with affective outcomes. These results run counter to the idea that being affectively ready for the worst has psychological benefits, suggesting that instead, anticipatory negative affect can come with affective costs

mobileQ: A free user-friendly application for collecting experience sampling data.

In this article we introduce mobileQ, which is a free, open-source platform that our lab has developed to use in experience sampling studies. Experience sampling has several strengths and is becoming more widely conducted, but there are few free software options. To address this gap, mobileQ has freely available servers, a web interface, and an Android app. To reduce the barrier to entry, it requires no high-level programming and uses an easy, point-and-click interface. It is designed to be used on dedicated research phones, allowing for experimenter control and eliminating selection bias. In this article, we introduce setting up a study in mobileQ, outline the set of help resources available for new users, and highlight the success with which mobileQ has been used in our lab.status: publishe