ABSTRACT
Reallocating object-based attention across the visual field meridians is significantly faster horizontally than vertically (termed the shift direction anisotropy; SDA), implicating the meridians in reorienting object-based attention. Here, we tested the modulatory role of the meridians in the emergence of the SDA by manipulating meridian local feature contrast. Considering the notion of separate pools of attentional resources in each cortical hemisphere, we hypothesised that manipulating the horizontal meridian would selectively modulate the SDA. In four experiments, participants were presented with an "L"-shaped object and detected a target that appeared at either a cued location or at one of two equidistant non-cued locations at the far end of the horizontal or vertical object arm. Meridian local feature contrast was manipulated with perceptually strong enhancements (visible lines and colour contrast borders) and perceptually weak enhancements (illusory borders from line texture patterns and inducers). Weak enhancements of the meridians did not significantly modulate SDA magnitude; however, during perceptually strong enhancements of the horizontal meridian, the SDA was significantly reduced compared with both vertical meridian enhancement and no-enhancement conditions. Moreover, horizontal and vertical shift RTs were statistically equivalent when the horizontal meridian was enhanced with a visible line, our strongest manipulation, indicating the SDA was eliminated. These results suggest that the SDA emerges due to reallocating object-based attention across the horizontal meridian. We interpret this finding as evidence in support of the theory by which anatomical segregations of the visual system determine how pools of attentional resources resolve competition between and within cortical hemispheres.
ABSTRACT
Spatial navigation is supported by visual cues (e.g., scenes, schemas like arrows, and words) that must be comprehended quickly to facilitate effective transit. People comprehend spatial directions faster from schemas and words than scenes. We hypothesize that this occurs because schemas and words efficiently engage space-based attention, allowing for less costly computations. Here, participants completed a spatial cueing paradigm, and we calculated cue validity effects - how much faster participants responded to validly than invalidly cued locations - for each cue format. We pre-registered Experiment 1 and found significant cue validity effects with schemas and words, but not scenes, suggesting space-based attention was allocated more efficiently with schemas and words than scenes. In Experiment 2, we explicitly instructed participants to interpret the scenes from an egocentric perspective and found that this instruction manipulation still did not result in a significant cue validity effect with scenes. In Experiment 3, we investigated whether the differential effects between conditions were due to costly computations to extract spatial direction and found that increasing cue duration had no influence. In Experiment 4, significant cue validity effects were observed for orthogonal but not non-orthogonal spatial directions, suggesting space-based attention was allocated more efficiently when the spatial direction precisely matched the target location. These findings confirm our hypothesis that efficient allocation of space-based attention is guided by faster spatial direction comprehension. Altogether, this work suggests that schemas and words may be more effective supports than scenes for navigation performance in the real-world.
ABSTRACT
People tend to think they are not susceptible to change blindness and overestimate their ability to detect salient changes in scenes. Yet, despite their overconfidence, are individuals aware of and able to assess the relative difficulty of such changes? Here, we investigated whether participants' judgements of their ability to detect changes predicted their own change blindness. In Experiment 1, participants completed a standard change blindness task in which they viewed alternating versions of scenes until they detected what changed between the versions. Then, 6 to 7 months later, the same participants viewed the two versions and rated how likely they would be to spot the change. We found that changes rated as more likely to be spotted were detected faster than changes rated as more unlikely to be spotted. These metacognitive judgements continued to predict change blindness when accounting for low-level image properties (i.e., change size and eccentricity). In Experiment 2, we used likelihood ratings from a new group of participants to predict change blindness durations from Experiment 1. We found that there was no advantage to using participants' own metacognitive judgements compared to those from the new group to predict change blindness duration, suggesting that differences among images (rather among individuals) contribute the most to change blindness. Finally, in Experiment 3, we investigated whether metacognitive judgements are based on the semantic similarity between the versions of the scene. One group of participants described the two versions of the scenes, and an independent group rated the similarity between the descriptions. We found that changes rated as more similar were judged as being more difficult to detect than changes rated as less similar; however, semantic similarity (based on linguistic descriptions) did not predict change blindness. These findings reveal that (1) people can rate the relative difficulty of different changes and predict change blindness for different images and (2) metacognitive judgements of change detection likelihood are not fully explained by low-level and semantic image properties.
Subject(s)
Metacognition , Awareness , Blindness , Humans , Judgment , SemanticsABSTRACT
Object-based attention (OBA) enhances processing within the boundaries of a selected object. Larger OBA effects have been observed for horizontal compared to vertical rectangles, which were eliminated when controlling for attention shifts across the visual field meridians. We aimed to elucidate the modulatory role of the meridians on OBA. We hypothesized that the contralateral organization of visual cortex accounts for these differences in OBA prioritization. Participants viewed "L"-shaped objects and, following a peripheral cue at the object vertex, detected the presence of a target at the cued location (valid), or at a non-cued location (invalid) offset either horizontally or vertically. In Experiment 1, the single displayed object contained components crossing both meridians. In Experiment 2, one cued object and one non-cued object were displayed such that both crossed the meridians. In Experiment 3, one cued object was sequestered into one screen quadrant, with its vertex either near or far from fixation. Results from Experiments 1 and 2 revealed a horizontal shift advantage (faster RTs for horizontal shifts across the vertical meridian compared to vertical shifts across the horizontal meridian), regardless of whether shifts take place within a cued object (Experiment 1) or between objects (Experiment 2). Results from Experiment 3 revealed no difference between horizontal and vertical shifts for objects that were positioned far from fixation, although the horizontal shift advantage reappeared for objects near fixation. These findings suggest a critical modulatory role of visual field meridians in the efficiency of reorienting object-based attention.
