Additivity of grouping by proximity and luminance similarity is dependent on relative grouping strength: An analysis of individual differences in grouping sensitivity.

It has previously been shown that grouping by proximity is well described by a linear function relating the perceived orientation of a dot lattice to the ratio of the distances between the dots in the different orientations. Similarly, luminance influences how observers perceptually group stimuli. Using the dot lattice paradigm, it has been shown that proximity and luminance similarity interact additively, which means that their effects can be summed to predict an observers' percept. In this study, we revisit the additive interplay between proximity and luminance similarity and we ask whether this pattern might be the result of inappropriately averaging different types of observers or the imbalance between the strength of proximity grouping and luminance similarity grouping. To address these questions, we first ran a replication of the original study reporting the additive interplay between proximity and luminance similarity. Our results showed a convincing replication at the aggregate and individual level. However, at the individual level, all observers showed grouping by proximity whereas some observers did not show grouping by luminance similarity. In response, we ran a second experiment with enlarged luminance differences to reinforce the strength of grouping by luminance similarity and balance the strength of the two grouping cues. Interestingly, in this second experiment, additivity was not observed but instead a significant interaction was obtained. This disparity suggests that the additivity or interaction between two grouping cues in a visual stimulus is not a general rule of perceptual grouping but a consequence of relative grouping strength.

Contributions of low- and high-level contextual mechanisms to human face perception.

Contextual modulations at primary stages of visual processing depend on the strength of local input. Contextual modulations at high-level stages of (face) processing show a similar dependence to local input strength. Namely, the discriminability of a facial feature determines the amount of influence of the face context on that feature. How high-level contextual modulations emerge from primary mechanisms is unclear due to the scarcity of empirical research systematically addressing the functional link between the two. We tested (62) young adults' ability to process local input independent of the context using contrast detection and (upright and inverted) morphed facial feature matching tasks. We first investigated contextual modulation magnitudes across tasks to address their shared variance. A second analysis focused on the profile of performance across contextual conditions. In upright eye matching and contrast detection tasks, contextual modulations only correlated at the level of their profile (averaged Fisher-Z transformed r = 1.18, BF10 > 100), but not magnitude (r = .15, BF10 = .61), suggesting the functional independence but similar working principles of the mechanisms involved. Both the profile (averaged Fisher-Z transformed r = .32, BF10 = 9.7) and magnitude (r = .28, BF10 = 4.58) of the contextual modulations correlated between inverted eye matching and contrast detection tasks. Our results suggest that non-face-specialized high-level contextual mechanisms (inverted faces) work in connection to primary contextual mechanisms, but that the engagement of face-specialized mechanisms for upright faces obscures this connection. Such combined study of low- and high-level contextual modulations sheds new light on the functional relationship between different levels of the visual processing hierarchy, and thus on its functional organization.

Same stimulus, same temporal context, different percept? Individual differences in hysteresis and adaptation when perceiving multistable dot lattices.

How we perceptually organize a visual stimulus depends not only on the stimulus itself, but also on the temporal and spatial context in which the stimulus is presented and on the individual processing the stimulus and context. Earlier research found both attractive and repulsive context effects in perception: tendencies to organize visual input similarly to preceding context stimuli (i.e., hysteresis, attraction) co-exist with tendencies that repel the current percept from the organization that is most dominant in these contextual stimuli (i.e., adaptation, repulsion). These processes have been studied mostly on a group level (e.g., Schwiedrzik et al., 2014). Using a Bayesian hierarchical model comparison approach, the present study (N = 75) investigated whether consistent individual differences exist in these attractive and repulsive temporal context effects, with multistable dot lattices as stimuli. In addition, the temporal stability of these individual differences in context effects was investigated, and it was studied how the strength of these effects related to the strength of individual biases for absolute orientations. The results demonstrate that large individual differences in the size of attractive and repulsive context effects exist. Furthermore, these individual differences are highly consistent across timepoints (one to two weeks apart). Although almost everyone showed both effects in the expected direction, not every single individual did. In sum, the study reveals differences in how individuals combine previous input and experience with current input in their perception, and more generally, this teaches us that different individuals can perceive identical stimuli differently, even within a similar context.

The Value of Bayesian Methods for Accurate and Efficient Neuropsychological Assessment.

OBJECTIVE: Clinical neuropsychology has been slow in adopting novelties in psychometrics, statistics, and technology. Researchers have indicated that the stationary nature of clinical neuropsychology endangers its evidence-based character. In addition to a technological crisis, there may be a statistical crisis affecting clinical neuropsychology. That is, the frequentist null hypothesis significance testing framework remains the dominant approach in clinical practice, despite a recent surge in critique on this framework. While the Bayesian framework has been put forward as a viable alternative in psychology in general, the possibilities it offers to clinical neuropsychology have not received much attention. METHOD: In the current position paper, we discuss and reflect on the value of Bayesian methods for the advancement of evidence-based clinical neuropsychology. RESULTS: We aim to familiarize clinical neuropsychologists and neuropsychological researchers to Bayesian methods of inference and provide a clear rationale for why these methods are valuable for clinical neuropsychology. CONCLUSION: We argue that Bayesian methods allow for a more intuitive answer to our diagnostic questions and form a more solid foundation for sequential and adaptive diagnostic testing, representing uncertainty about patients' observed test scores and cognitive modeling of test results.

Perception of the ambiguous motion quartet: A stimulus-observer interaction approach.

Visual perception is the result of a highly complex process depending on both stimulus and observer characteristics and, importantly, their interactions. Generating robust theories and making precise predictions in light of this complexity can be challenging, and the interaction of stimulus- and observer-related effects is often neglected or understated. In the current study, we examined inter- and intra-individual differences and the effects of a wide range of three stimulus characteristics (i.e., spatial distance, temporal distance, and spatial location). Our results indicate that not all individuals show the same group average stimulus-driven effects on the perception of a motion quartet and that these effects are not always equal across the entire stimulus range. Moreover, we observed that there are clear individual differences in spontaneous perceptual dynamics and that these can be overridden by some but not all stimulus manipulations. We conclude that considering different stimulus manipulations, different observers, and their interactions can provide a more nuanced and informative view on the processes governing visual perception. This study examines the effect of spatial distance, spatiotemporal distance, spatial location, and individual differences on the perception of the ambiguous motion quartet.

Combined frequency-tagging EEG and eye-tracking measures provide no support for the "excess mouth/diminished eye attention" hypothesis in autism.

BACKGROUND: Scanning faces is important for social interactions. Difficulty with the social use of eye contact constitutes one of the clinical symptoms of autism spectrum disorder (ASD). It has been suggested that individuals with ASD look less at the eyes and more at the mouth than typically developing (TD) individuals, possibly due to gaze aversion or gaze indifference. However, eye-tracking evidence for this hypothesis is mixed. While gaze patterns convey information about overt orienting processes, it is unclear how this is manifested at the neural level and how relative covert attention to the eyes and mouth of faces might be affected in ASD. METHODS: We used frequency-tagging EEG in combination with eye tracking, while participants watched fast flickering faces for 1-min stimulation sequences. The upper and lower halves of the faces were presented at 6 Hz and 7.5 Hz or vice versa in different stimulation sequences, allowing to objectively disentangle the neural saliency of the eyes versus mouth region of a perceived face. We tested 21 boys with ASD (8-12 years old) and 21 TD control boys, matched for age and IQ. RESULTS: Both groups looked longer at the eyes than the mouth, without any group difference in relative fixation duration to these features. TD boys looked significantly more to the nose, while the ASD boys looked more outside the face. EEG neural saliency data partly followed this pattern: neural responses to the upper or lower face half were not different between groups, but in the TD group, neural responses to the lower face halves were larger than responses to the upper part. Face exploration dynamics showed that TD individuals mostly maintained fixations within the same facial region, whereas individuals with ASD switched more often between the face parts. LIMITATIONS: Replication in large and independent samples may be needed to validate exploratory results. CONCLUSIONS: Combined eye-tracking and frequency-tagged neural responses show no support for the excess mouth/diminished eye gaze hypothesis in ASD. The more exploratory face scanning style observed in ASD might be related to their increased feature-based face processing style.

Individual differences in processing orientation and proximity as emergent features.

Numerous examples of meaningful inter-individual differences in visual processing have been documented in low- and high-level vision. For mid-level vision or perceptual organization, vision scientists have only recently started to study the inter-individual differences structure. In this study, we focus on orientation and proximity as emergent features and combine a quantitative information processing approach with an individual differences approach. We first replicated the results reported in Hawkins, Houpt, Eidels, and Townsend (2016) in a set of 52 observers. That is, observers showed higher processing capacity for detecting a change in a stimulus configuration when the emergent features orientation or proximity were changed. Next, we asked whether individual differences processing capacities were similar across emergent features. The capacity to detect any type of change correlated moderately across individuals, whereas the capacity to detect changes in either emergent feature alone was not strongly correlated. This indicates that there is no general sensitivity to emergent features and that observers can be good at detecting orientation changes whilst being poor at detecting proximity changes (and vice versa). An additional exploratory multivariate analysis of the data revealed that response times and accuracies correlated strongly within each emergent feature. Moreover, specific factors related to change detection and inward displacements were observed, revealing consistent individual differences in our data. We discuss the results in the context of the literature on individual differences in vision where both specific, fragmented factors as well as broad, general factors have been reported.

Contrast versus identity encoding in the face image follow distinct orientation selectivity profiles.

Orientation selectivity is a fundamental property of primary visual encoding. High-level processing stages also show some form of orientation dependence, with face identification preferentially relying on horizontally-oriented information. How high-level orientation tuning emerges from primary orientation biases is unclear. In the same group of participants, we derived the orientation selectivity profile at primary and high-level visual processing stages using a contrast detection and an identity matching task. To capture the orientation selectivity profile, we calculated the difference in performance between all tested orientations (0, 45, 90, and 135°) for each task and for upright and inverted faces, separately. Primary orientation selectivity was characterized by higher sensitivity to oblique as compared to cardinal orientations. The orientation profile of face identification showed superior horizontal sensitivity to face identity. In each task, performance with upright and inverted faces projected onto qualitatively similar a priori models of orientation selectivity. Yet the fact that the orientation selectivity profiles of contrast detection in upright and inverted faces correlated significantly while such correlation was absent for identification indicates a progressive dissociation of orientation selectivity profiles from primary to high-level stages of orientation encoding. Bayesian analyses further indicate a lack of correlation between the orientation selectivity profiles in the contrast detection and face identification tasks, for upright and inverted faces. From these findings, we conclude that orientation selectivity shows distinct profiles at primary and high-level stages of face processing and that a transformation must occur from general cardinal attenuation when processing basic properties of the face image to horizontal tuning when encoding more complex properties such as identity.

Configural superiority for varying contrast levels.

Observers can search for a target stimulus at a particular speed and accuracy. Adding an identical context to each stimulus can improve performance when the resulting stimuli form clearly discriminable configurations. This search advantage is known as the configural superiority effect (CSE). A recent study showed that embedding these stimuli in noise revealed lower contrast thresholds for part-stimuli compared to configural stimuli (Bratch et al., Journal of Experimental Psychology. Human Perception and Performance, 42(9), 1388-1398, 2016). This contrasts with the accuracy advantages traditionally associated with CSEs. In this study, we aimed to replicate the results of Bratch et al. and asked whether the benefit for part-stimuli held across the full psychometric function. Additionally, we tested whether embedding the stimuli in noise was crucial for obtaining their result and whether different contrast definitions affected the results. Furthermore, we used control stimuli that were more directly comparable. Our results showed a detection benefit for the Gestalt context stimuli in all conditions. Together, these results are in line with the literature on CSEs and do not seem to support the recent claim that Gestalts are processed less efficiently than part stimuli. Inspired by this, we sketch how contrast manipulations could be an additional tool to study how Gestalts are processed.

Sound-Symbolism Effects in the Absence of Awareness: A Replication Study.

People have been shown to link particular sounds with particular shapes. For instance, the round-sounding nonword bouba tends to be associated with curved shapes, whereas the sharp-sounding nonword kiki is deemed to be related to angular shapes. People's tendency to associate sounds and shapes has been observed across different languages. In the present study, we reexamined the claim by Hung, Styles, and Hsieh (2017) that such sound-shape mappings can occur before an individual becomes aware of the visual stimuli. More precisely, we replicated their first experiment, in which congruent and incongruent stimuli (e.g., bouba presented in a round shape or an angular shape, respectively) were rendered invisible through continuous flash suppression. The results showed that congruent combinations, on average, broke suppression faster than incongruent combinations, thus providing converging evidence for Hung and colleagues' assertions. Collectively, these findings now provide a solid basis from which to explore the boundary conditions of the effect.

Get the Picture? Goodness of Image Organization Contributes to Image Memorability.

According to Gestalt psychologists, goodness is a crucial variable for image organization. We hypothesized that these differences in goodness contribute to variability in image memorability. Building on this, we predicted that two characteristics of good organizations, (i) fast, efficient processing and (ii) robustness against transformations (e.g., shrinking), would be characteristic of memorable images. Two planned (Study 1, Study 2) and one follow-up (Study 3) study were conducted to test this. Study 1 operationalized fast processing as accuracy in a rapid-scene categorization task ("categorizability"). Study 2 operationalized robustness against shrinking as reaction time in a thumbnail search task ("shrinkability"). We used 44 real-life scene images of 14 semantic categories from a previous memorability study. Each image was assigned a categorizability and shrinkability score. The predicted positive relation between categorizability and memorability was not observed in Study 1. A post-hoc explanation attributed this null result to a masking role of image distinctiveness. Furthermore, memorable images were located faster in the thumbnail search task, as predicted, but Study 2 could not rule whether this was merely a result of their distinctiveness. To elucidate these results, Study 3 quantified the images on distinctiveness and statistically controlled for this variable in a reanalysis of Study 1 and Study 2. When distinctiveness was controlled for, categorizability and memorability did show a significant positive correlation. Moreover, the results also argued against the alternative explanation of the results of Study 2. Taken together, the results support the hypothesis that goodness of organization contributes to image memorability.

Does task relevance shape the 'shift to global' in ambiguous motion perception?

Perception can differ even when the stimulus information is the same. Previous studies have demonstrated the importance of experience and relevance on visual perception. We examined the influence of perceptual relevance in an auxiliary task on subsequent perception of an ambiguous stimulus. Observers were presented with an ambiguous motion stimulus that could either be perceived as rotating dot pairs ("local") or pulsating geometrical figures ("global"). Prolonged perception of this stimulus is characterized by a "shift to global", but it remained unclear whether this process is due to relevance of the global percept or mere exposure to the stimulus. During a relevance learning phase over 5 successive days, participants were divided into conditions determining the relevant percept in an auxiliary task: local, global, or none (active exposure). In a pre- and posttest, individual points of subjective equality between local and global percepts were measured. Results indicate that there is indeed a shift to global. Interestingly, auxiliary task relevance does not seem to modify this process.

Unconscious arithmetic: Assessing the robustness of the results reported by Karpinski, Briggs, and Yale (2018).

In 2012, a study by Sklar et al. reported that participants could solve invisible subtractions. This notion of unconscious arithmetic has been influential because it challenges current theories of consciousness. In 2016, Karpinski et al. published a direct replication reporting evidence for unconscious addition rather than subtraction. About a year later, the study was retracted due to a computation error in the analysis pipeline. After this error was corrected, no evidence for unconscious addition nor subtraction was obtained. Recently, Karpinski et al. republished the study by applying the exclusion criteria used in Sklar et al. The reanalysis found weak evidence for unconscious subtraction. To assess the robustness of these results, we examine how sensitive the results are to data analytic decisions. We outline a set of 250 analyses that we consider justified to perform. We show that none of the analyses indicates evidence for unconscious subtraction.

The impact of video speed on the decision-making process of sports officials.

There is an increasing trend in association football (soccer) to assist referees in their decision-making with video technology. For decisions such as whether a goal has been scored or which player actually committed a foul, video technology can provide more objective information and be valuable to increase decisional accuracy. It is unclear, however, to what extent video replays can aid referee decisions in the case of foul-play situations in which the decision is typically more ambiguous. In this study, we specifically evaluated the impact of slow-motion replays on decision-making by referees. To this end, elite referees of five different countries (n = 88) evaluated 60 different foul-play situations taken from international matches, replayed in either real time or slow motion. Our results revealed that referees penalized situations more severely in slow motion compared to real time (e.g. red card with a yellow card reference decision). Our results provide initial evidence that video replay speed can have an important impact on the disciplinary decision given by the referee in case of foul play. The study also provides a real-life test-case for theories and insights regarding causality perception.

Alterations in the inferior longitudinal fasciculus in autism and associations with visual processing: a diffusion-weighted MRI study.

Background: One of the most reported neural features of autism spectrum disorder (ASD) is the alteration of multiple long-range white matter fiber tracts, as assessed by diffusion-weighted imaging and indexed by reduced fractional anisotropy (FA). Recent methodological advances, however, have shown that this same pattern of reduced FA may be an artifact resulting from excessive head motion and poorer data quality and that aberrant structural connectivity in children with ASD is confined to the right inferior longitudinal fasciculus (ILF). This study aimed at replicating the observation of reduced FA along the right ILF in ASD, while controlling for group differences in head motion and data quality. In addition, we explored associations between reduced FA in the right ILF and quantitative ASD characteristics, and the involvement of the right ILF in visual processing, which is known to be altered in ASD. Method: Global probabilistic tractography was performed on diffusion-weighted imaging data of 17 adolescent boys with ASD and 17 typically developing boys, matched for age, performance IQ, handedness, and data quality. Four tasks were administered to measure various aspects of visual information processing, together with questionnaires assessing ASD characteristics. Group differences were examined and the neural data were integrated with previously published findings using Bayesian statistics to quantify evidence for replication and to pool data and thus increase statistical power. (Partial) correlations were calculated to investigate associations between measures. Results: The ASD group showed consistently reduced FA only in the right ILF and slower performance on the visual search task. Bayesian statistics pooling data across studies confirmed that group differences in FA were confined to the right ILF only, with the evidence for altered FA in the left ILF being indecisive. Lower FA in the right ILF tended to covary with slower visual search and a more fragmented part-oriented processing style. Individual differences in FA of the right ILF were not reliably associated with the severity of ASD traits after controlling for clinical status. Conclusion: Our findings support the growing evidence for reduced FA along a specific fiber tract in ASD, the right ILF.

A critical reexamination of doing arithmetic nonconsciously.

A recent study claimed to have obtained evidence that participants can solve invisible multistep arithmetic equations (Sklar et al., 2012). The authors used a priming paradigm in which reaction times to targets congruent with the equation's solution were responded to faster compared with incongruent ones. We critically reanalyzed the data set of Sklar et al. and show that the claims being made in the article are not fully supported by the alternative analyses that we applied. A Bayesian reanalysis of the data accounting for the random variability of the target stimuli in addition to the subjects shows that the evidence for priming effects is less strong than initially claimed. That is, although Bayes factors revealed evidence for the presence of a priming effect, it was generally weak. Second, the claim that unconscious arithmetic occurs for subtraction but not for addition is not supported when the critical interaction is tested. Third, the data do not show well-established features of numerosity priming as derived from V-shaped response time curves for prime-target distances. Fourth, we show that it is impossible to classify reaction times as resulting from congruent or incongruent prime-target relationships, which should be expected if their results imply that participants genuinely solve the equations on each trial. We conclude that the claims being made in the original article are not fully supported by the analyses that we apply. Together with a recent failure to replicate the original results and a critique of the analysis based on regression to the mean, we argue that the current evidence for unconscious arithmetic is inconclusive. We argue that strong claims require strong evidence and stress that cumulative research strategies are needed to provide such evidence.

If we accept that poor replication rates are mainstream.

We agree with the authors' arguments to make replication mainstream but contend that the poor replication record is symptomatic of a pre-paradigmatic science. Reliable replication in psychology requires abandoning group-level p-value testing in favor of real-time predictions of behaviors, mental and brain events. We argue for an approach based on analysis of boundary conditions where measurement is closely motivated by theory.