Attentional priming releases crowding

Atten Percept Psychophys Attentional priming releases crowding rni Kristjnsson 0 1 Ptur Rnar Heimisson 0 1 Gunnar Freyr Rbertsson 0 1 David Whitney 0 1 0 D. Whitney Department of Psychology, University of California , Berkeley, CA , USA 1 A. Kristjansson Institute of Cognitive Neuroscience, University College London , London , UK Views of natural scenes unfold over time, and objects of interest that were present a moment ago tend to remain present. While visual crowding places a fundamental limit on object recognition in cluttered scenes, most studies of crowding have suffered from the limitation that they typically involved static scenes. The role of temporal continuity in crowding has therefore been unaddressed. We investigated intertrial effects upon crowding in visual scenes, showing that crowding is considerably diminished when objects remain constant on consecutive visual search trials. Repetition of both the target and distractors decreases the critical distance for crowding from flankers. More generally, our results show how object continuity through between-trial priming releases objects that would otherwise be unidentifiable due to crowding. Crowding, although it is a significant bottleneck on object recognition, can be mitigated by statistically likely temporal continuity of the objects. Crowding therefore depends not only on what is momentarily present, but also on what was previously attended. On a crowded basketball court, teammates must be found and opponents avoided. Team colors are key features remaining Crowding; Attention; Priming; Spatial vision - constant while the players move around. While visual crowding may impair recognition of objects (and teammates) in such cluttered scenes (Levi, 2008; Pelli & Tillman, 2008; Whitney & Levi, 2011) the impact of crowding on object recognition is typically studied with individual static scenes. But views of natural scenes unfold over time, and objects of interest that were present a moment ago tend to remain present. No studies of crowding have systematically examined whether visual processing at one moment modulates recognition in subsequent cluttered scenes. Effects of continued task relevance have been examined in visual search tasks (Maljkovic & Nakayama, 1994). When the same visual search repeats, performance is improved (see Kristjnsson & Campana, 2010; Lamy & Kristjnsson, 2013, for reviews). Such priming effects are surprisingly large, modulating response times and accuracy by as much as 30 %. According to most accounts, priming reflects facilitated attention shifts (Becker; Chun & Nakayama, 2000; Kristjnsson & Nakayama; Lamy, Antebi, Aviani, & Carmel, 2008). Priming effects have been observed during very brief presentation, excluding any role of response facilitation (sgeirsson, Kyllingsbaek, Kristjnsson, & Bundesen, 2012; Sigurdardottir, Kristjnsson, & Driver, 2008; Yashar & Lamy, 2010). Additionally, priming effects are fundamentally bound to attentional selection (Brascamp, Blake, & Kristjnsson, 2011; Goolsby & Suzuki, 2001). Yeshurun and Rashal (2010) reported increased identification accuracy from attentional precues for a target stimulus appearing among flankers (see also Dakin, Bex, Cass, & Watt, 2009; Freeman & Pelli, 2007; Strasburger, 2005). The cue reduced the critical distance for crowding indicating that attention reduces the spatial extent of crowding. If attention modulates crowding, we should therefore expect attentional priming to modulate crowding. The prediction is straightforward: the more often the same search type repeats, interference from flankers upon search performance will be diminished. Here, we asked whether crowding from flankers is affected when the visual search targets to be attended and distractors to be avoided are constant between trials. Visual search trials were interspersed with crowding trials (see Fig. 1A). Observers located the oddly colored grating (red or green) and determined its orientation among three distractors of the other color (70-ms unmasked presentation). On 35 % of the trials, task-irrelevant flankers appeared along with the search items (crowding trials) on the same radial line from fixation as the target and distractors (at variable distances from the target). Since priming typically builds up gradually and is larger the more often that search repeats (see, e.g., Kristjnsson, 2008; Maljkovic & Nakayama, 1994), a second prediction was that effects upon crowding should decrease with more priming. If crowding is not a temporally independent process, then previous information (i.e., priming) about object properties should result in diminished crowding with increased priming. In Experiment 1, the target and distractors swapped roles between trials. Since target and distractor repetition have dissociable effects upon attentional priming (Kristjnsson & Driver, 2005, 2008; Lamy et al., 2008), in Experiments 2 and 3 we addressed the independent influence of target and distractor repetition on crowding. Observers searched for an odd-color-out target among three distractors (Fig. 1). On 65 % of the trials, only search items appeared, whereas four flankers appeared along with them on Fig. 1 Experimental design and results from Experiment 1. (A) Three possible consecutive search trials: on the right a crowding trial with flankers, following two search-only trials. The preceding trials share target and distractor colors with the crowding trial. The four flankers appear along with the search display on trial N . The items are not drawn to scale, and target and distractor locations were not predictable, except that they were always 90 radial degrees apart, whereas locations on the imaginary circle varied randomly. When flankers appeared (on 35 % of the trials), they appeared on the same four radial axes from center as the target and distractors. (B) Average percents correct on crowding trials as a function of how often the same search type repeated. The dots denote the average percents correct on no-flanker trials. (C) Probit fits to the mean percent correct scores for the 12 observers, as a function of search repetition. (D) Average thresholds, estimated from the individual psychometric functions the other 35 % (see Fig. 1A). We assessed how crowding was influenced by the number of similar search trials (with constant target and distractors) preceding each crowding display. Participants A group of 12 nave observers (eight female) participated in 600 trials. All had normal or corrected-tonormal vision. Stimuli On search-only trials, four 1.8 disks (viewing distance = 60 cm) containing stripes oriented 45 away from vertical appeared (see Fig. 1A). The target was the oddly colored item (either red [41 cdm2 ] or green [56 cdm2 ]), and the three other items of opposite color were distractors. Observers indicated by a keypress whether the target was oriented left or right from vertical. The search items appeared on an imaginary circle (radius from the c (...truncated)