Attentional oblique effect when judging simultaneity
ABSTRACT We extended the investigation of the oblique effect in two novel ways: from stimulus-driven vision to visual attention and from space to time. Participants fixated the center of briefly flashed displays that contained a temporally varying Gabor stimulus in each of the four peripheral quadrants. Across trial blocks, we manipulated which two of the four peripheral stimuli were to be selected for a simultaneity judgment. Simultaneity judgments were significantly worse for obliquely (diagonally) attended targets than for cardinally (horizontally or vertically) attended targets, despite identical retinal stimulation across all attentional conditions. The impairment in judging the simultaneity of obliquely attended targets occurred between and within lateral hemifields, despite significantly greater temporal acuity for the left hemifield. The oblique effect in simultaneity judgments disappeared when the same targets were presented without temporally varying stimuli at distractor locations-a finding that implicates selective attention. Intriguingly, the oblique effect in excluding stimuli at distractor locations also disappeared when participants viewed the original displays but attended to spatial frequency rather than to simultaneity. These findings raise the possibility of different spatial integration windows when attending to spatial versus temporal features, even when those features are co-presented in space and time.
- SourceAvailable from: Ragnhild Eg[Show abstract] [Hide abstract]
ABSTRACT: In well-controlled laboratory experiments, researchers have found that humans can perceive delays between auditory and visual signals as short as 20 ms. Conversely, other experiments have shown that humans can tolerate audiovisual asynchrony that exceeds 200 ms. This seeming contradiction in human temporal sensitivity can be attributed to a number of factors such as experimental approaches and precedence of the asynchronous signals, along with the nature, duration, location, complexity and repetitiveness of the audiovisual stimuli, and even individual differences. In order to better understand how temporal integration of audiovisual events occurs in the real world, we need to close the gap between the experimental setting and the complex setting of everyday life. With this work, we aimed to contribute one brick to the bridge that will close this gap. We compared perceived synchrony for long-running and eventful audiovisual sequences to shorter sequences that contain a single audiovisual event, for three types of content: action, music, and speech. The resulting windows of temporal integration showed that participants were better at detecting asynchrony for the longer stimuli, possibly because the long-running sequences contain multiple corresponding events that offer audiovisual timing cues. Moreover, the points of subjective simultaneity differ between content types, suggesting that the nature of a visual scene could influence the temporal perception of events. An expected outcome from this type of experiment was the rich variation among participants' distributions and the derived points of subjective simultaneity. Hence, the designs of similar experiments call for more participants than traditional psychophysical studies. Heeding this caution, we conclude that existing theories on multisensory perception are ready to be tested on more natural and representative stimuli.Frontiers in Psychology 05/2015; 6(736). DOI:10.3389/fpsyg.2015.00736 · 2.80 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Background / Purpose: In our previous study, Gabor stimuli were presented in four corners of a screen (14.55 deg diagonally from fixation) and changed orientation synchronously or asynchronously. Two were pre-cued as targets on each trial. Participants judged whether or not the change in orientation happened simultaneously for the cued targets. Performance (d’) was significantly worse for target pairs that were diagonally rather than horizontally or vertically aligned.Here we present new data and error analyses (false alarms vs. misses) demonstrating that this oblique effect when attending to simultaneity reflects erroneously integrated information from irrelevant spatial locations. That is, the oblique effect arose from false alarms, not misses. Main conclusion: This excessive spatial integration for obliquely attended targets occurred between and within lateral hemifields, despite significantly greater temporal acuity (demonstrated by a significantly lower miss rate) in the left hemifield. Within-hemifield data were obtained by moving the fixation point from the center of the screen to either side, such that the stimuli on the screen fell entirely within either the left or the right hemifield.A perceptual learning experiment demonstrated that the effect was task specific: significant learning on the simultaneity task did not generalize to a task with identical displays wherein participants judged spatial frequency differences rather than simultaneity. This suggests different spatial integration windows for different attended features (simultaneity versus spatial frequency), even when those features are co-presented in space and time.Vision Sciences Society 11th Annual Meeting 2011; 07/2011
- [Show abstract] [Hide abstract]
ABSTRACT: Prior reports demonstrate that simultaneity is judged less precisely in the right visual field (RVF) than in the left visual field (LVF). The present psychophysical study was conducted to provide new information about why and when (i.e., the visual information stage at which) RVF deficits arise in simultaneity judgments. In Experiment 1, participants judged either the simultaneity or the relative spatial frequency of Gabor targets in the right or left hemifield while distractors were randomly absent or present. When attention was not needed to exclude distractors, signal detection theory analyses revealed an RVF simultaneity deficit with an error pattern that implicates low RVF temporal acuity, not excessive RVF neural noise. Adding attentionally demanding distractors introduced a separate, significant RVF simultaneity deficit with error patterns that implicate the inappropriate integration of temporal asynchronies from distractor locations. Neither the distractor-independent RVF acuity deficit nor the distractor-induced RVF excessive spatial integration occurred for spatial frequency discrimination at the same retinal locations. In Experiment 2, a perceptual learning procedure significantly improved RVF simultaneity judgments. The learning was task-specific but generalized to the untrained (left) visual field and to novel retinal locations. This observation implicates the simultaneity decision as the visual information stage that sets the limit on performance.Journal of Vision 08/2012; 12(2). DOI:10.1167/12.2.1 · 2.73 Impact Factor