The study of consciousness is considered by many one of the most difficult contemporary scientifi... more The study of consciousness is considered by many one of the most difficult contemporary scientific endeavors and confronts several methodological and theoretical challenges. A central issue that makes the study of consciousness so challenging is that, while the rest of science is concerned with problems that can be verified from a "third person" view (i.e., objectively), the study of consciousness deals with the phenomenon of subjective experience, only accessible from a "first person" view. In the present article, we review early (starting during the late 19th century) and later efforts on measuring consciousness and its absence, focusing on the two main approaches used by researchers within the field: objective (i.e., performance based) and subjective (i.e., report based) measures of awareness. In addition, we compare the advantages and disadvantages of both types of awareness measures, evaluate them according to different methodological considerations, and discuss, among other issues, the possibility of comparing them by transforming them to a common sensitivity measure (d′). Finally, we explore several new approachessuch as Bayesian models to support the absence of awareness or new machine-learning based decoding models-as well as future challenges-such as measuring the qualia, the qualitative contents of awareness-in consciousness research. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
The dissociation between conscious and unconscious perception is one of the most relevant issues ... more The dissociation between conscious and unconscious perception is one of the most relevant issues in the study of human cognition. While there is evidence suggesting that some stimuli might be unconsciously processed up to its meaning (e.g., high-level stimulus processing), some authors claim that most results on the processing of subliminal stimuli can be explained by a mixture of methodological artefacts and questionable assumptions about what can be considered non-conscious. Particularly, one of the most controversial topics involves the method by which the awareness of the stimuli is assessed. To address this question, we introduced an integrative approach to assess the extent to which masked hierarchical stimuli (i.e., global shapes composed of local elements) can be processed in the absence of awareness. We combined a priming task where participants had to report global or local shapes, with the use of subjective and objective awareness measures collected either in a separate block (offline), or trial-by-trial during the main task (online). The unconscious processing of the masked primes was then evaluated through two different novel model-based methods: a Bayesian and a General Recognition Theory modeling approach. Despite the high correlation between awareness measures, our results show that the use of alternative approaches based on different theoretical assumptions leads to diverging conclusions about the extent of the unconscious processing of the masked primes.
To investigate whether local elements are grouped into global shapes in the absence of awareness,... more To investigate whether local elements are grouped into global shapes in the absence of awareness, we introduced two different masked priming designs (e.g., the classic dissociation paradigm and a trial-wise probe and prime discrimination task) and collected both objective (i.e., performance based) and subjective (using the perceptual awareness scale [PAS]) awareness measures. Prime visibility was manipulated using three different prime-mask stimulus onset asynchronies (SOAs) and an unmasked condition. Our results showed that assessing prime visibility trial-wise heavily interfered with masked priming preventing any prime facilitation effect. The implementation of Bayesian regression models, which predict priming effects for participants whose awareness levels are at chance level, provided strong evidence in favor of the hypothesis that local elements group into global shape in the absence of awareness for SOAs longer than 50 ms, suggesting that prime-mask SOA is a crucial factor in the processing of the global shape without awareness.
In the present study, we will introduce a novel masked priming design comprising both objective (... more 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.
Supplemental material, sj-docx-2-qjp-10.1177_17470218211010486 for Competition between perceptual... more Supplemental material, sj-docx-2-qjp-10.1177_17470218211010486 for Competition between perceptual grouping cues in an indirect objective task by Cristina Villalba-García, Mikel Jimenez, Dolores Luna, José A Hinojosa and Pedro R Montoro in Quarterly Journal of Experimental Psychology
¿Cómo "emerge" un estímulo en nuestra consciencia? Los datos más recientes parecen apoy... more ¿Cómo "emerge" un estímulo en nuestra consciencia? Los datos más recientes parecen apoyar la hipótesis del nivel de procesamiento, según la cual una representación de alto nivel de un estímulo (p.ej., la percepción del significado de una palabra) aparece en nuestra consciencia de una forma abrupta o dicotómica, mientras que una representación de bajo nivel (p.ej., la percepción del color de un estímulo) emerge de forma más gradual. El reto para la ciencia de la consciencia consiste ahora en integrar estos nuevos resultados con las teorías cognitivas y neurocientíficas ya existentes.
Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on ... more Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on object recognition. Here, we investigated the processing level at which crowding occurs by exploring the type of crowding errors (global, local, or both). Twenty-seven observers estimated the orientation of a target when presented alone or surrounded by flankers (local shapes). Flankers were aligned to create an illusory rectangle (enhanced global configuration) or misaligned (reduced global configuration). We analyzed the error distributions by fitting probabilistic mixture models. Results showed that often participants 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. Thus, crowding might be characterized as...
Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on ... more 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...
Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on ... more 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.
Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on ... more 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. Recognition of objects is limited by their spacing. When objects are too close together, they become indistinguishable, a phenomenon known as crowding. Crowding sets a fundamental limit on conscious visual perception 1 and impairs reading, eye and hand movements, visual search and other functions in typical peripheral and central amblyopic vision 2 . The study of crowding has gained increased attention in recent years, and our knowledge of crowding characteristics is substantial 1,3-5 . For example, crowding impairs target identification but not detection 6,7 and it depends on both target eccentricity and the distance between target and flankers (i.e., the critical spacing, 0.3-0.5 of target eccentricity) 7-10 (but see ). In addition, crowding depends on the similarity between the target and the flankers, such that flankers more similar to the target (e.g., in color, shape, depth, spatial frequency or complexity) produce stronger crowding . Nonetheless, the underlying processes by which crowding occurs are still unclear. Most of the prevailing theories of crowding propose that crowding occurs because of the integration or ''pooling'' of low-level features at a single, relatively early stage of visual processing , in line with the classic hierarchical model of object recognition . In these models, information proceeds from the processing of low-level visual features (such as spatial frequency, orientation or color) to the perception of coherent forms, shapes and complex objects. Importantly, the input of higher-level visual areas would be fully determined by the outputs of basic, lower-level feature detectors, and thus information lost at early stages of visual processing would be irretrievably lost . If crowding occurs due to the averaging of low-level visual features between target and flankers at an early visual stage, it would disrupt the formation of any higher-level target representation, and crowding would represent an early bottleneck of human vision. However, in contrast to the prediction of a strict "pooling" or averaging mechanism, crowding errors often reflect reports of a flanker instead of the target-known as misreport errors . Interestingly, misreport errors
Supplemental material, sj-docx-1-qjp-10.1177_17470218211010486 for Competition between perceptual... more Supplemental material, sj-docx-1-qjp-10.1177_17470218211010486 for Competition between perceptual grouping cues in an indirect objective task by Cristina Villalba-García, Mikel Jimenez, Dolores Luna, José A Hinojosa and Pedro R Montoro in Quarterly Journal of Experimental Psychology
The integration between Gestalt grouping cues has been a relatively unexplored issue in vision sc... more 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 individual analysis and both revealed a consistent pattern of processing dominance of: (1) luminance simila...
In the present study, we conducted two experiments (Experiment 1: 35 participants, M = 29; SD = 8... more 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, η2p = .31 and p = .016, η2p = .16, respectively), but, crucially, no significant priming differences between illusory and grouping primes across SOA conditions. Overall, our results are important i...
The level of processing (LoP) hypothesis proposes that low-level stimulus perception (i.e., stimu... more 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 individual 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 divergence 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, Bclarity^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.
Previous research on perceptual organization operations still provides contradictory evidence on ... more 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 divided 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.
The level of processing hypothesis (LoP) proposes that the transition from unaware to aware visua... more 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 to 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, whereas 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...
In the present study, we will introduce a novel masked priming design comprising both objective (... more 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.
The study of consciousness is considered by many one of the most difficult contemporary scientifi... more The study of consciousness is considered by many one of the most difficult contemporary scientific endeavors and confronts several methodological and theoretical challenges. A central issue that makes the study of consciousness so challenging is that, while the rest of science is concerned with problems that can be verified from a "third person" view (i.e., objectively), the study of consciousness deals with the phenomenon of subjective experience, only accessible from a "first person" view. In the present article, we review early (starting during the late 19th century) and later efforts on measuring consciousness and its absence, focusing on the two main approaches used by researchers within the field: objective (i.e., performance based) and subjective (i.e., report based) measures of awareness. In addition, we compare the advantages and disadvantages of both types of awareness measures, evaluate them according to different methodological considerations, and discuss, among other issues, the possibility of comparing them by transforming them to a common sensitivity measure (d′). Finally, we explore several new approachessuch as Bayesian models to support the absence of awareness or new machine-learning based decoding models-as well as future challenges-such as measuring the qualia, the qualitative contents of awareness-in consciousness research. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
The dissociation between conscious and unconscious perception is one of the most relevant issues ... more The dissociation between conscious and unconscious perception is one of the most relevant issues in the study of human cognition. While there is evidence suggesting that some stimuli might be unconsciously processed up to its meaning (e.g., high-level stimulus processing), some authors claim that most results on the processing of subliminal stimuli can be explained by a mixture of methodological artefacts and questionable assumptions about what can be considered non-conscious. Particularly, one of the most controversial topics involves the method by which the awareness of the stimuli is assessed. To address this question, we introduced an integrative approach to assess the extent to which masked hierarchical stimuli (i.e., global shapes composed of local elements) can be processed in the absence of awareness. We combined a priming task where participants had to report global or local shapes, with the use of subjective and objective awareness measures collected either in a separate block (offline), or trial-by-trial during the main task (online). The unconscious processing of the masked primes was then evaluated through two different novel model-based methods: a Bayesian and a General Recognition Theory modeling approach. Despite the high correlation between awareness measures, our results show that the use of alternative approaches based on different theoretical assumptions leads to diverging conclusions about the extent of the unconscious processing of the masked primes.
To investigate whether local elements are grouped into global shapes in the absence of awareness,... more To investigate whether local elements are grouped into global shapes in the absence of awareness, we introduced two different masked priming designs (e.g., the classic dissociation paradigm and a trial-wise probe and prime discrimination task) and collected both objective (i.e., performance based) and subjective (using the perceptual awareness scale [PAS]) awareness measures. Prime visibility was manipulated using three different prime-mask stimulus onset asynchronies (SOAs) and an unmasked condition. Our results showed that assessing prime visibility trial-wise heavily interfered with masked priming preventing any prime facilitation effect. The implementation of Bayesian regression models, which predict priming effects for participants whose awareness levels are at chance level, provided strong evidence in favor of the hypothesis that local elements group into global shape in the absence of awareness for SOAs longer than 50 ms, suggesting that prime-mask SOA is a crucial factor in the processing of the global shape without awareness.
In the present study, we will introduce a novel masked priming design comprising both objective (... more 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.
Supplemental material, sj-docx-2-qjp-10.1177_17470218211010486 for Competition between perceptual... more Supplemental material, sj-docx-2-qjp-10.1177_17470218211010486 for Competition between perceptual grouping cues in an indirect objective task by Cristina Villalba-García, Mikel Jimenez, Dolores Luna, José A Hinojosa and Pedro R Montoro in Quarterly Journal of Experimental Psychology
¿Cómo "emerge" un estímulo en nuestra consciencia? Los datos más recientes parecen apoy... more ¿Cómo "emerge" un estímulo en nuestra consciencia? Los datos más recientes parecen apoyar la hipótesis del nivel de procesamiento, según la cual una representación de alto nivel de un estímulo (p.ej., la percepción del significado de una palabra) aparece en nuestra consciencia de una forma abrupta o dicotómica, mientras que una representación de bajo nivel (p.ej., la percepción del color de un estímulo) emerge de forma más gradual. El reto para la ciencia de la consciencia consiste ahora en integrar estos nuevos resultados con las teorías cognitivas y neurocientíficas ya existentes.
Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on ... more Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on object recognition. Here, we investigated the processing level at which crowding occurs by exploring the type of crowding errors (global, local, or both). Twenty-seven observers estimated the orientation of a target when presented alone or surrounded by flankers (local shapes). Flankers were aligned to create an illusory rectangle (enhanced global configuration) or misaligned (reduced global configuration). We analyzed the error distributions by fitting probabilistic mixture models. Results showed that often participants 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. Thus, crowding might be characterized as...
Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on ... more 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...
Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on ... more 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.
Crowding refers to the inability to recognize objects in clutter, setting a fundamental limit on ... more 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. Recognition of objects is limited by their spacing. When objects are too close together, they become indistinguishable, a phenomenon known as crowding. Crowding sets a fundamental limit on conscious visual perception 1 and impairs reading, eye and hand movements, visual search and other functions in typical peripheral and central amblyopic vision 2 . The study of crowding has gained increased attention in recent years, and our knowledge of crowding characteristics is substantial 1,3-5 . For example, crowding impairs target identification but not detection 6,7 and it depends on both target eccentricity and the distance between target and flankers (i.e., the critical spacing, 0.3-0.5 of target eccentricity) 7-10 (but see ). In addition, crowding depends on the similarity between the target and the flankers, such that flankers more similar to the target (e.g., in color, shape, depth, spatial frequency or complexity) produce stronger crowding . Nonetheless, the underlying processes by which crowding occurs are still unclear. Most of the prevailing theories of crowding propose that crowding occurs because of the integration or ''pooling'' of low-level features at a single, relatively early stage of visual processing , in line with the classic hierarchical model of object recognition . In these models, information proceeds from the processing of low-level visual features (such as spatial frequency, orientation or color) to the perception of coherent forms, shapes and complex objects. Importantly, the input of higher-level visual areas would be fully determined by the outputs of basic, lower-level feature detectors, and thus information lost at early stages of visual processing would be irretrievably lost . If crowding occurs due to the averaging of low-level visual features between target and flankers at an early visual stage, it would disrupt the formation of any higher-level target representation, and crowding would represent an early bottleneck of human vision. However, in contrast to the prediction of a strict "pooling" or averaging mechanism, crowding errors often reflect reports of a flanker instead of the target-known as misreport errors . Interestingly, misreport errors
Supplemental material, sj-docx-1-qjp-10.1177_17470218211010486 for Competition between perceptual... more Supplemental material, sj-docx-1-qjp-10.1177_17470218211010486 for Competition between perceptual grouping cues in an indirect objective task by Cristina Villalba-García, Mikel Jimenez, Dolores Luna, José A Hinojosa and Pedro R Montoro in Quarterly Journal of Experimental Psychology
The integration between Gestalt grouping cues has been a relatively unexplored issue in vision sc... more 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 individual analysis and both revealed a consistent pattern of processing dominance of: (1) luminance simila...
In the present study, we conducted two experiments (Experiment 1: 35 participants, M = 29; SD = 8... more 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, η2p = .31 and p = .016, η2p = .16, respectively), but, crucially, no significant priming differences between illusory and grouping primes across SOA conditions. Overall, our results are important i...
The level of processing (LoP) hypothesis proposes that low-level stimulus perception (i.e., stimu... more 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 individual 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 divergence 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, Bclarity^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.
Previous research on perceptual organization operations still provides contradictory evidence on ... more 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 divided 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.
The level of processing hypothesis (LoP) proposes that the transition from unaware to aware visua... more 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 to 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, whereas 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...
In the present study, we will introduce a novel masked priming design comprising both objective (... more 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.
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Papers by Mikel Jimenez
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.
Drafts by Mikel Jimenez
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.