ORCID Profile
0000-0002-2006-6782
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Publisher: Center for Open Science
Date: 12-12-2022
Abstract: In the present study, we will introduce a novel masked priming design comprising both objective (i.e., performance based) and subjective (i.e., visibility reports, gathered through the perceptual awareness scale PAS) awareness measures to study whether local elements are grouped into global (square and diamond) shapes in the absence of awareness. Prime visibility will be manipulated using three different prime-mask stimulus onset asynchronies (SOAs) and an unmasked condition. We will investigate whether the introduction of online measures of awareness (e.g., PAS) affects priming effects, as well as explore the relation between objective awareness performance and subjective awareness reports using a common sensitivity measure (d’). The introduction of Bayesian analyses and generative regression models will complement the evidence provided by linear mixed models and will allow us to evaluate the results in favor -or against- the null hypotheses across the different experiments.
Publisher: SAGE Publications
Date: 22-04-2021
DOI: 10.1177/17470218211010486
Abstract: The integration between Gestalt grouping cues has been a relatively unexplored issue in vision science. The present work introduces an objective indirect method based on the repetition discrimination task to determine the rules that govern the dominance dynamics of the competition between both intrinsic (Experiment 1: proximity vs luminance similarity) and extrinsic grouping cues (Experiment 2: common region vs connectedness) by means of objective measures of grouping (reaction times and accuracy). Prior to the main task, a novel objective equating task was introduced with the aim of equating the grouping strength of the cues for the visuomotor system. The main task included two single conditions with the grouping cues acting alone as well as two competing conditions displaying the grouping factors pitted against one another. Conventional aggregated analyses were combined with in idual analysis and both revealed a consistent pattern of processing dominance of: (1) luminance similarity over proximity and (2) common region over connectedness. Interestingly, the in idual analyses showed that, despite the heterogeneous responses to the single conditions, the pattern of dominance between cues was robustly homogeneous among the participants in the competing conditions.
Publisher: Elsevier BV
Date: 10-2023
Publisher: Cambridge University Press (CUP)
Date: 2018
DOI: 10.1017/SJP.2018.47
Abstract: In the present study, we conducted two experiments (Experiment 1: 35 participants, M = 29 SD = 8.4 Experiment 2: 36 participants, M = 25 SD = 6.1) with the intention to explore whether underlying perceptual grouping operations and illusory form perception generate dissociable priming effects when Kanizsa-like figures are presented as primes and the rotated inducers as controls under conditions of restricted awareness. Using five different stimulus onset asynchronies (SOA conditions, Experiment 1: 27, 40 and 53 ms Experiment 2: 27, 80 and 227 ms), we displayed masked illusory and groping primes that could be congruent or incongruent in their orientation with subsequent probe stimuli (vertical vs. horizontal). We found significant priming effects in both Experiment 1 and 2 ( p .001, η 2 p = .31 and p = .016, η 2 p = .16, respectively), but, crucially, no significant priming differences between illusory and grouping primes across SOA conditions. Overall, our results are important in showing that a dissociation of the percept generated by the grouping of the inducers from that generated by the illusory form is crucial in the study of illusory form perception under conditions of restricted awareness. In addition, they provide further evidence of perceptual organization operations occurring under very restrictive awareness conditions.
Publisher: Elsevier BV
Date: 08-2017
DOI: 10.1016/J.CONCOG.2017.05.004
Abstract: Previous research on perceptual organization operations still provides contradictory evidence on whether the integration of sparse local elements into coherently unified shapes and the construction of the illusory form are accomplished without the need of awareness. In the present study, three experiments were conducted in which participants were presented with masked (Experiment 1, SOA=27ms Experiment 2 SOA=53ms) and unmasked (Experiment 3) primes consisting of geometric shapes (a square or a diamond) that could be congruent or incongruent with subsequent probe stimuli (square vs. diamond). Furthermore, the primes were ided into: a grouping condition (where local elements may group together into global shapes), an illusory condition (where the arrangement of local elements produced illusory shapes) and a hybrid condition (where both operations were presented simultaneously). While no priming effects were found for the shortest SOA (27ms), both grouping and illusory primes produced significant priming effects in the longer SOA (53ms). On the other hand, results in Experiment 3 (unmasked) showed strong priming effects for the grouping of the inducers in both the grouping and the hybrid conditions, and also a significant but weaker priming effect for the illusory condition. Overall, our results support the possibility of the integration of local visual features into a global shape in the absence of awareness and, likewise, they suggest an early -subliminal- construction of the illusory shape, implying that feedback projections from higher to lower visual areas are not crucial in the construction of the illusory form.
Publisher: Elsevier BV
Date: 12-2018
DOI: 10.1016/J.NEUROPSYCHOLOGIA.2018.11.001
Abstract: A crucial view in the graded vs. dichotomous debate on visual awareness proposes that its graded or dichotomous nature may depend on the depth of stimulus processing (or level of processing) associated to the experimental task. In the present study, we explored the behavioral patterns and neural correlates of different degrees of awareness associated to different depths (i.e. low vs. high) of stimulus processing. The low-level stimulus condition consisted of detecting the location of the target based on its brightness characteristics, whereas the high-level stimulus condition consisted of identifying which of four possible targets (numbers/letters) had appeared. Behavioral results showed that both subjective ratings of awareness and accuracy levels increased linearly as a function of awareness and independently of the level of stimulus processing. Additionally, the electrophysiological recordings revealed two correlates of visual awareness: enhanced posterior negativity in the N200 time window (VAN, visual awareness negativity) and enhanced positivity in the P3 time window (LP, late positivity). Interestingly, we found evidence of awareness levels modulating N200/VAN litudes in a graded manner only for the low-level task, whereas P3/LP litudes were modulated in a graded manner for both low and high-level tasks. The finding that the early posterior correlate of visual awareness (VAN at 150-250 ms) was sensitive to level of processing is consistent with task effects occurring in the visual cortex and supports the view that it is mediated by attention to task-relevant features. The litudes of P3/LP in both tasks correlate more directly with graded awareness and behavioral accuracy.
Publisher: Springer Science and Business Media LLC
Date: 25-04-2022
DOI: 10.1038/S41598-022-10685-Z
Abstract: Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on various perceptual tasks such as reading and facial recognition. While prevailing models suggest that crowding is a unitary phenomenon occurring at an early level of processing, recent studies have shown that crowding might also occur at higher levels of representation. Here we investigated whether local and global crowding interference co-occurs within the same display. To do so, we tested the distinctive contribution of local flanker features and global configurations of the flankers on the pattern of crowding errors. Observers (n = 27) estimated the orientation of a target when presented alone or surrounded by flankers. Flankers were grouped into a global configuration, forming an illusory rectangle when aligned or a rectangular configuration when misaligned. We analyzed the error distributions by fitting probabilistic mixture models. Results showed that participants often misreported the orientation of a flanker instead of that of the target. Interestingly, in some trials the orientation of the global configuration was misreported. These results suggest that crowding occurs simultaneously across multiple levels of visual processing and crucially depends on the spatial configuration of the stimulus. Our results pose a challenge to models of crowding with an early single pooling stage and might be better explained by models which incorporate the possibility of multilevel crowding and account for complex target-flanker interactions.
Publisher: MIT Press - Journals
Date: 06-2021
DOI: 10.1162/JOCN_A_01712
Abstract: The level of processing hypothesis (LoP) proposes that the transition from unaware to aware visual perception is graded for low-level (i.e., energy, features) stimulus whereas dichotomous for high-level (i.e., letters, words, meaning) stimulus. In this study, we explore the behavioral patterns and neural correlates associated with different depths (i.e., low vs. high) of stimulus processing. The low-level stimulus condition consisted of identifying the color (i.e., blue/blueish vs. red/reddish) of the target, and the high-level stimulus condition consisted of identifying stimulus category (animal vs. object). Behavioral results showed that the levels of processing manipulation produced significant differences in both the awareness rating distributions and accuracy performances between tasks, the low-level task producing more intermediate subjective ratings and linearly increasing accuracy performances and the high-level task producing less intermediate ratings and a more nonlinear pattern for accuracies. The electrophysiological recordings revealed two correlates of visual awareness, an enhanced posterior negativity in the N200 time window (visual awareness negativity [VAN]), and an enhanced positivity in the P3 time window (late positivity [LP]). The analyses showed a double dissociation between awareness and the level of processing hypothesis manipulation: Awareness modulated VAN litudes only in the low-level color task, whereas LP litude modulations were observed only in the higher level category task. These findings are compatible with a two-stage microgenesis model of conscious perception, where an early elementary phenomenal sensation of the stimulus (i.e., the subjective perception of color) would be indexed by VAN, whereas stimulus' higher level properties (i.e., the category of the target) would be reflected in the LP in a later latency range.
Publisher: Springer Science and Business Media LLC
Date: 29-04-2019
DOI: 10.3758/S13414-019-01732-5
Abstract: The level of processing (LoP) hypothesis proposes that low-level stimulus perception (i.e., stimulus energy and features) is a graded process whereas high-level (i.e., letters, words, meaning) stimulus perception is all-or-none. In the present study, we set up a visual masking design in order to examine the nature of visual awareness at stimulus energy (i.e., detection task) and feature levels (identification task) at specific in idual target durations (13, 27, 40, 53, and 80 ms). We manipulated the strength of the masking to produce different visibility conditions and gathered participants' subjective (across a 4-point awareness scale) and objective (accuracy levels) awareness performances. We found that intermediate ratings (i.e., ratings 2 and 3, which index graded awareness experiences) were used in more than 50% of the trials for target presentations of 27, 40, 53, and 80 ms. In addition, objective accuracy performances for target presentations of 27 and 80 ms produced linearly increasing detection and identification accuracies across the awareness scale categories, respectively. Overall, our results suggest that visual awareness at energy and feature levels of stimulus perception may be graded. Furthermore, we found a ergence in detection and identification performance results, which emphasizes the need for an adequate election of target durations when studying different perceptual processes such as detection versus more complex stimulus identification processes. Finally, "clarity" in the perceptual awareness scale should be exhaustively defined depending on the level of processing of the stimulus, as participants may recalibrate the meaning of the different awareness categories depending on task demands.
Publisher: Elsevier BV
Date: 10-2020
Location: Australia
Start Date: 2017
End Date: 2018
Funder: Banco Santander
View Funded ActivityStart Date: 2017
End Date: 2018
Funder: Banco Santander Central Hispano SA
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