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Leys, G.

Publications and source records attributed to Leys, G..

3 recordsLinked to original sources

The representational dynamics of the animal appearance bias in human visual cortex are indicative of fast feedforward processing

The human visual system has a seemingly unique tendency to interpret zoomorphic objects as animals, not as objects. This animal appearance bias is very strong in the ventral visual pathway as measured through functional magnetic resonance imaging (fMRI), but it is absent in feedforward deep convolutional neural networks. Here we investigate how this bias emerges over time by probing its representational dynamics through multivariate electroencephalography (EEG). The initially activated representations to lookalike zoomorphic objects are very similar to the representations activated by animal pictures and very different from the neural responses to regular objects. Neural responses that reflect the true identity of the zoomorphic objects as inanimate objects are weaker and appear later, as do effects of task context. The strong early emergence of an animal appearance bias strongly supports a feedforward explanation, indicating that lack of recurrence in deep neural networks is not an explanation for their failure to show this bias.

neuroscience↗

Object-scene conceptual regularities reveal fundamental differences between biological and artificial object vision

Human vision is still largely unexplained. Computer vision made impressive progress on this front, but it is still unclear to which extent artificial neural networks approximate human object vision at the behavioral and neural levels. Here, we investigated whether machine object vision mimics the representational hierarchy of human object vision with an experimental design that allows testing within-domain representations for animals and scenes, as well as across-domain representations reflecting their real-world contextual regularities such as animal-scene pairs that often co-occur in the visual environment. We found that DCNNs trained in object recognition acquire representations, in their late processing stage, that closely capture human conceptual judgements about the co-occurrence of animals and their typical scenes. Likewise, the DCNNs representational hierarchy shows surprising similarities with the representational transformations emerging in domain-specific ventrotemporal areas up to domain-general frontoparietal areas. Despite these remarkable similarities, the underlying information processing differs. The ability of neural networks to learn a human-like high-level conceptual representation of object-scene co-occurrence depends upon the amount of object-scene co-occurrence present in the image set thus highlighting the fundamental role of training history. Further, although mid/high-level DCNN layers represent the category division for animals and scenes as observed in VTC, its information content shows reduced domain-specific representational richness. To conclude, by testing within- and between-domain selectivity while manipulating contextual regularities we reveal unknown similarities and differences in the information processing strategies employed by human and artificial visual systems. Author SummaryComputational object vision represents the new frontier of brain models, but do current artificial visual systems known as deep convolutional neural networks (DCNNs) represent the world as humans do? Our results reveal that DCNNs are able to capture important representational aspects of human vision both at the behavioral and neural levels. At the behavioral level, DCNNs are able to pick up contextual regularities of objects and scenes thus mimicking human high-level semantic knowledge such as learning that a polar bear "lives" in ice landscapes. At the neural representational level, DCNNs capture the representational hierarchy observed in the visual cortex all the way up to frontoparietal areas. Despite these remarkable correspondences, the information processing strategies implemented differ. In order to aim for future DCNNs to perceive the world as humans do, we suggest the need to consider aspects of training and tasks that more closely match the wide computational role of human object vision over and above object recognition.

neuroscience↗

Thought Control Failure: Sensory Determinants and Functional Effects

The ability to control ones thoughts is important for mental wellbeing, attention, focus, future planning and ideation. While there is a long history of research into thought control, the inherent subjectivity of thoughts has made objective investigation, and thus mechanistic understanding difficult. Here, we report a novel method to empirically investigate thought control success and failure by objectively measuring the sensory strength of visual thoughts. We use the perceptual illusion binocular rivalry to assess emergent images in mind during two common thought control strategies: thought suppression and thought substitution. Thought suppression was ineffective, suppressed thoughts primed subsequent rivalry dominance at the same level as intentionally imagined thoughts. This priming effect was disrupted by concurrent uniform luminance and changes in retinotopic location, suggesting early visual representations/traces. While individuals showed some metacognition of thought suppression, strikingly, the perceptual effects remained even when thoughts were reported as successfully suppressed, indicating these thoughts may exist outside of reportable awareness. In contrast, thought substitution was more effective in controlling the perceptual effects and showed good metacognition. A thought control index predicted greater levels of trait mindfulness, while high levels of anxiety and schizotypy were related to poor thought control. Overall, our findings offer a novel method to track thoughts before and after they emerge into awareness and suggest that non-reportable and involuntary thoughts form visual representations pivotal to thought control failure.

neuroscience↗