Fractal dimension and the navigational information provided by natural scenes

Zahedi, Moosarreza Shamsyeh; Zeil, Jochen

doi:10.1371/journal.pone.0196227

Cited by 8 publications

(4 citation statements)

References 33 publications

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“…It is unclear why this might be. Speculatively, the stimuli in Experiment 1 were matched for perceived contrast, and so speculatively, this may have had an impact on the results, as fractal dimension is related to image contrast, specifically pixel variance (Shamsyeh Zahedi & Zeil, 2018). This can also be seen in the current study, when RMS contrast was controlled (Experiment 2) there was a positive relationship between spectral slope and fractal dimension—the higher the spatial frequency content, the more complex the image.…”

Section: Resultsmentioning

confidence: 99%

Steady‐state visual evoked potential responses predict visual discomfort judgements

O’Hare

Hird

Whybrow

2021

Eur J of Neuroscience

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It has been suggested that aesthetically pleasing stimuli are processed efficiently by the visual system, whereas uncomfortable stimuli are processed inefficiently. This study consists of a series of three experiments investigating this idea using a range of images of abstract artworks, photographs of natural scenes, and computer‐generated stimuli previously shown to be uncomfortable. Subjective judgements and neural correlates were measured using electroencephalogram (EEG) (steady‐state visual evoked potentials, SSVEPs). In addition, global image statistics (contrast, Fourier amplitude spectral slope and fractal dimension) were taken into account. When effects of physical image contrast were controlled, fractal dimension predicted discomfort judgements, suggesting the SSVEP response is more likely to be influenced by distribution of edges than the spectral slope. Importantly, when effects of physical contrast and fractal dimension were accounted for using linear mixed effects modelling, SSVEP responses predicted subjective judgements of images. Specifically, when stimuli were not matched for perceived contrast, there was a positive relationship between SSVEP responses and how pleasing a stimulus was judged to be, and conversely a negative relationship between discomfort and SSVEP response. This is significant as it shows that the neural responses in early visual areas contribute to the subjective (un)pleasantness of images, although the results of this study do not provide clear support for the theory of efficient coding as the cause of perceived pleasantness or discomfort of images, and so other explanations need to be considered.

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Section: Resultsmentioning

confidence: 99%

Steady‐state visual evoked potential responses predict visual discomfort judgements

O’Hare

Hird

Whybrow

2021

Eur J of Neuroscience

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“…In brief, the VM approach assumes that the animal records a view of the area surrounding the goal and then moves so as to minimize the discrepancy between the recorded and the actual view. The memorized “view” is not simply understood as a mental image but instead as a set of encoded parameters including depth, motion, edges, or specific features, e.g., skyline and fractional position of mass (Möller 2001 ; Collett and Collett 2002 ; Zahedi and Zeil 2018 ; Graham and Cheng 2009 ; Lent et al 2013 ).…”

Section: Introductionmentioning

confidence: 99%

Geometry-based navigation in the dark: layout symmetry facilitates spatial learning in the house cricket, Acheta domesticus, in the absence of visual cues

et al. 2022

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The capacity to navigate by layout geometry has been widely recognized as a robust strategy of place-finding. It has been reported in various species, although most studies were performed with vision-based paradigms. In the presented study, we aimed to investigate layout symmetry-based navigation in the house cricket, Acheta domesticus, in the absence of visual cues. For this purpose, we used a non-visual paradigm modeled on the Tennessee Williams setup. We ensured that the visual cues were indeed inaccessible to insects. In the main experiment, we tested whether crickets are capable of learning to localize the centrally positioned, inconspicuous cool spot in heated arenas of various shapes (i.e., circular, square, triangular, and asymmetric quadrilateral). We found that the symmetry of the arena significantly facilitates crickets’ learning to find the cool spot, indicated by the increased time spent on the cool spot and the decreased latency in locating it in subsequent trials. To investigate mechanisms utilized by crickets, we analyzed their approach paths to the spot. We found that crickets used both heuristic and directed strategies of approaching the target, with the dominance of a semi-directed strategy (i.e., a thigmotactic phase preceding direct navigation to the target). We propose that the poor performance of crickets in the asymmetrical quadrilateral arena may be explained by the difficulty of encoding its layout with cues from a single modality.

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“…Unlike conventional psychophysics and perception stimuli, fractals are non-Euclidian and structurally complex, with each of the parts being similar to the whole. This allows for insight into configural (as opposed to featural) processes such as natural scene perception ( Zahedi & Zeil, 2018 ), spatial navigation ( Juliani et al, 2016 ), Gestalt grouping principles ( Farkas & Hajnal, 2013 ), and object recognition in computer vision and machine learning algorithms ( Domenech et al, 2020 ; Tan & Yan, 1999 , 2000 ; Wang et al, 2016 ) and in humans ( Bies et al, 2016 ; Taylor et al, 2017 ). Fractals hold potential for such areas of research because their qualities (e.g.…”

Section: Introductionmentioning

confidence: 99%

Parametric Cortical Representations of Complexity and Preference for Artistic and Computer-Generated Fractal Patterns Revealed by Single-Trial EEG Power Spectral Analysis

et al. 2021

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Fractals are self-similar patterns that repeat at different scales, the complexity of which are expressed as a fractional Euclidean dimension D between 0 (a point) and 2 (a filled plane). The drip paintings of American painter Jackson Pollock (JP) are fractal in nature, and Pollock’s most illustrious works are of the high-D (~1.7) category. This would imply that people prefer more complex fractal patterns, but some research has instead suggested people prefer lower-D fractals. Furthermore, research has suggested that parietal and frontal brain activity tracks the complexity of fractal patterns, but previous research has artificially binned fractals depending on fractal dimension, rather than treating fractal dimension as a parametrically varying value. We used white layers extracted from JP artwork as stimuli, and constructed statistically matched 2-dimensional random Cantor sets as control stimuli. We recorded the electroencephalogram (EEG) while participants viewed the JP and matched random Cantor fractal patterns. Participants then rated their subjective preference for each pattern. We used a single-trial analysis to construct within-subject models relating subjective preference to fractal dimension D, as well as relating D and subjective preference to single-trial EEG power spectra. Results indicated that participants preferred higher-D images for both JP and Cantor stimuli. Power spectral analysis showed that, for artistic fractal images, parietal alpha and beta power parametrically tracked complexity of fractal patterns, while for matched mathematical fractals, parietal power tracked complexity of patterns over a range of frequencies, but most prominently in alpha band. Furthermore, parietal alpha power parametrically tracked aesthetic preference for both artistic and matched Cantor patterns. Overall, our results suggest that perception of complexity for artistic and computer-generated fractal images is reflected in parietal-occipital alpha and beta activity, and neural substrates of preference for complex stimuli are reflected in parietal alpha band activity.

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Fractal dimension and the navigational information provided by natural scenes

Cited by 8 publications

References 33 publications

Steady‐state visual evoked potential responses predict visual discomfort judgements

Steady‐state visual evoked potential responses predict visual discomfort judgements

Geometry-based navigation in the dark: layout symmetry facilitates spatial learning in the house cricket, Acheta domesticus, in the absence of visual cues

Parametric Cortical Representations of Complexity and Preference for Artistic and Computer-Generated Fractal Patterns Revealed by Single-Trial EEG Power Spectral Analysis

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