Exposure to images of urban environments affords higher cognitive processing demands than exposur... more Exposure to images of urban environments affords higher cognitive processing demands than exposure to images of nature scenes; an effect potentially related to differences in low-level image statistics such as fractals. The aim of the current study was to investigate whether the fractal dimensions of an abstract scene affect cognitive processing demands, using gait kinematics as a measure of cognitive demand. Participants (n = 40) were asked to walk towards different types of synthetic images which were parametrically varied in their fractal dimensions. At the end of each walk, participants rated each image for its visual discomfort (n = 20) or for its likability (n = 20) as potential confounding factors. Fractal dimensions were predictors of walking speed. Moreover, the interaction between fractal dimensions and subjective visual discomfort but not liking predicted velocity. Overall, these data suggest that fractal dimensions indeed contribute to environmentally induced cognitive p...
The amplitude of Fourier spectra for natural scenes falls with spatial frequency (f) and is descr... more The amplitude of Fourier spectra for natural scenes falls with spatial frequency (f) and is described by the equation, 1/fα, where exponent α corresponds to the slope of the spectral drop-off. For natural scenes α takes on intermediate values ~1.25, reflecting their scale invariance. It is also well-established that, on average, images with natural scene statistics are preferred to those that deviate from these properties. Although this average pattern of preference for images with the intermediate values of α is robust, there are also marked individual differences in preference for different levels of α. This study investigated the effects of adaptation on average and individual visual preferences for synthetic filtered noise images varying in α. Participant preferences (N = 58) were measured via a 2AFC task prior to adaptation (baseline) and post-adaptation There were 3 adaptation conditions (α = 0.25, 1.25, 2.25) and 5 test levels of α (0.25, 0.75, 1.25, 1.75, 2.25). On average, the adaptation elevated preferences for test images with α matching the adaptor conditions, especially in adaptor conditions, α = 0.25 and 2.25. We also observed marked individual differences in preference for different levels of α. These different preference profiles remained stable throughout the experiment and affected the levels of adaptation observed in different adaptation conditions.
Stimuli and data from Nguyen & Spehar - Visual adaptation to natural scene statistics and vis... more Stimuli and data from Nguyen & Spehar - Visual adaptation to natural scene statistics and visual preference. Visual preference was measured using a two alternative forced choice (2AFC) paired comparison procedure. On each trial, two images were presented side by side and the task was to indicate, via keypress, which of the two images was visually preferred. In our experiment visual preference was measured for synthetic noise images with spectral slope alpha of 0.25, 0.75, 1.25, 1.75 and 2.25. Each level of alpha was paired with every other level resulting in a total of 20 unique pairs for one experimental sequence. Within each experimental sequence every alpha level was shown eight times in total; four times as the left image in a pair and four times as the right image in a pair. There were six blocks in total: three baseline blocks and three adaptation blocks. These blocks alternated such that a baseline block always preceded an adaptation block. In other words, the blocks were split into three different baseline-adaptation pairs. The three baseline blocks consisted of trials in which the five alpha levels (0.25, 0.75, 1.25, 1.75 and 2.25) were paired with each other as described above. The two images in any given pair had the same Fourier phase but the Fourier phase varied randomly between different pairs. The three adaptation blocks were the same as the baseline blocks except that each adaptation block was preceded by an adaptation period of 150 seconds to one of the three adapting alpha levels:, alpha = 0.25, 1.25 and 2.25. The order of different adaptation conditions (0.25, 1.25 or 2.25) was randomised across participants. In total, each participant underwent six blocks. For the majority of participants (40/54), each of the three baseline and three adaptation blocks consisted of 40 trials in total (20 unique pairings repeated twice), resulting in 240 trials in total. For the remaining 18 participants, each of the baseline and adaptation blocks contained 20 trials, resulting in 120 experimental trials in [...]
The 1/fα amplitude spectrum is a statistical property of natural scenes characterising a specific... more The 1/fα amplitude spectrum is a statistical property of natural scenes characterising a specific distribution of spatial and temporal frequencies and their associated luminance intensities. This property has been studied extensively in the spatial domain whereby sensitivity and visual preference overlap and peak for slopes within the natural range (α ≈ 1), but remains relatively less studied in the temporal domain. Here, we used a 4AFC task to measure sensitivity and a 2AFC task to measure visual preference and across a wide range of spatial (α = 0.25, 1.25, 2.25) and temporal (α = 0.25 to 2.50, step size: 0.25) slope conditions. Stimuli with a shallow temporal slope modulate rapidly (e.g. 0.25), whereas stimuli with a steep slope modulate slowly (e.g. 2.25). Interestingly, sensitivity and visual preference did not closely overlap. While the sensitivity of the visual system is highest for our stimulus with an intermediate modulation rate (1.25), which is most abundant in nature, the stimulus with the slowest modulation rate (2.25) was most preferred. It seems sensible for the visual system to be sensitive to spatiotemporal spectra that most commonly exist in nature (α ≈ 1). However, it is possible that preference might be related to what these properties signal in the natural world. Consider the cases of waves slowly vs. rapidly crashing on a beach or fast vs. slow animals. In both instances the slowest option is often the safest and preferential, suggesting that the temporal 1/fα amplitude spectrum provides additional information that may indicate preferred environmental conditions.
The investigation of aesthetics has primarily been conducted within the visual domain. This is no... more The investigation of aesthetics has primarily been conducted within the visual domain. This is not a surprise, as aesthetics has largely been associated with the perception and appreciation of visual media, such as traditional artworks, photography, and architecture. However, one doesn’t need to look far to realize that aesthetics extends beyond the visual domain. Media such as film and music introduce a unique and equally rich temporally changing visual and auditory experience. Product design, ranging from furniture to clothing, strongly depends on pleasant tactile evaluations. Studies involving the perception of 1/f statistics in vision have been particularly consistent in demonstrating a preference for a 1/f structure resembling that of natural scenes, as well as systematic individual differences across a variety of visual objects. Interestingly, comparable findings have also been reached in the auditory and tactile domains. In this review, we discuss some of the current literatu...
Decades of research have resulted in a detailed understanding of the retinotopic layout of early ... more Decades of research have resulted in a detailed understanding of the retinotopic layout of early visual areas V1 and V2, but a less detailed understanding of V3 and V4. The central ends of these retinotopic maps join together and form the foveal confluence. Using electrophysiology or cytoarchitecture mapping the precise organisation of visual areas in this foveal confluence has proven difficult. Ironically, therefore the most important region of the visual field maps has remained'terra incognita'. We used fMRI with 1.2× 1.2× 1.2 mm ...
Exposure to images of urban environments affords higher cognitive processing demands than exposur... more Exposure to images of urban environments affords higher cognitive processing demands than exposure to images of nature scenes; an effect potentially related to differences in low-level image statistics such as fractals. The aim of the current study was to investigate whether the fractal dimensions of an abstract scene affect cognitive processing demands, using gait kinematics as a measure of cognitive demand. Participants (n = 40) were asked to walk towards different types of synthetic images which were parametrically varied in their fractal dimensions. At the end of each walk, participants rated each image for its visual discomfort (n = 20) or for its likability (n = 20) as potential confounding factors. Fractal dimensions were predictors of walking speed. Moreover, the interaction between fractal dimensions and subjective visual discomfort but not liking predicted velocity. Overall, these data suggest that fractal dimensions indeed contribute to environmentally induced cognitive p...
The amplitude of Fourier spectra for natural scenes falls with spatial frequency (f) and is descr... more The amplitude of Fourier spectra for natural scenes falls with spatial frequency (f) and is described by the equation, 1/fα, where exponent α corresponds to the slope of the spectral drop-off. For natural scenes α takes on intermediate values ~1.25, reflecting their scale invariance. It is also well-established that, on average, images with natural scene statistics are preferred to those that deviate from these properties. Although this average pattern of preference for images with the intermediate values of α is robust, there are also marked individual differences in preference for different levels of α. This study investigated the effects of adaptation on average and individual visual preferences for synthetic filtered noise images varying in α. Participant preferences (N = 58) were measured via a 2AFC task prior to adaptation (baseline) and post-adaptation There were 3 adaptation conditions (α = 0.25, 1.25, 2.25) and 5 test levels of α (0.25, 0.75, 1.25, 1.75, 2.25). On average, the adaptation elevated preferences for test images with α matching the adaptor conditions, especially in adaptor conditions, α = 0.25 and 2.25. We also observed marked individual differences in preference for different levels of α. These different preference profiles remained stable throughout the experiment and affected the levels of adaptation observed in different adaptation conditions.
Stimuli and data from Nguyen & Spehar - Visual adaptation to natural scene statistics and vis... more Stimuli and data from Nguyen & Spehar - Visual adaptation to natural scene statistics and visual preference. Visual preference was measured using a two alternative forced choice (2AFC) paired comparison procedure. On each trial, two images were presented side by side and the task was to indicate, via keypress, which of the two images was visually preferred. In our experiment visual preference was measured for synthetic noise images with spectral slope alpha of 0.25, 0.75, 1.25, 1.75 and 2.25. Each level of alpha was paired with every other level resulting in a total of 20 unique pairs for one experimental sequence. Within each experimental sequence every alpha level was shown eight times in total; four times as the left image in a pair and four times as the right image in a pair. There were six blocks in total: three baseline blocks and three adaptation blocks. These blocks alternated such that a baseline block always preceded an adaptation block. In other words, the blocks were split into three different baseline-adaptation pairs. The three baseline blocks consisted of trials in which the five alpha levels (0.25, 0.75, 1.25, 1.75 and 2.25) were paired with each other as described above. The two images in any given pair had the same Fourier phase but the Fourier phase varied randomly between different pairs. The three adaptation blocks were the same as the baseline blocks except that each adaptation block was preceded by an adaptation period of 150 seconds to one of the three adapting alpha levels:, alpha = 0.25, 1.25 and 2.25. The order of different adaptation conditions (0.25, 1.25 or 2.25) was randomised across participants. In total, each participant underwent six blocks. For the majority of participants (40/54), each of the three baseline and three adaptation blocks consisted of 40 trials in total (20 unique pairings repeated twice), resulting in 240 trials in total. For the remaining 18 participants, each of the baseline and adaptation blocks contained 20 trials, resulting in 120 experimental trials in [...]
The 1/fα amplitude spectrum is a statistical property of natural scenes characterising a specific... more The 1/fα amplitude spectrum is a statistical property of natural scenes characterising a specific distribution of spatial and temporal frequencies and their associated luminance intensities. This property has been studied extensively in the spatial domain whereby sensitivity and visual preference overlap and peak for slopes within the natural range (α ≈ 1), but remains relatively less studied in the temporal domain. Here, we used a 4AFC task to measure sensitivity and a 2AFC task to measure visual preference and across a wide range of spatial (α = 0.25, 1.25, 2.25) and temporal (α = 0.25 to 2.50, step size: 0.25) slope conditions. Stimuli with a shallow temporal slope modulate rapidly (e.g. 0.25), whereas stimuli with a steep slope modulate slowly (e.g. 2.25). Interestingly, sensitivity and visual preference did not closely overlap. While the sensitivity of the visual system is highest for our stimulus with an intermediate modulation rate (1.25), which is most abundant in nature, the stimulus with the slowest modulation rate (2.25) was most preferred. It seems sensible for the visual system to be sensitive to spatiotemporal spectra that most commonly exist in nature (α ≈ 1). However, it is possible that preference might be related to what these properties signal in the natural world. Consider the cases of waves slowly vs. rapidly crashing on a beach or fast vs. slow animals. In both instances the slowest option is often the safest and preferential, suggesting that the temporal 1/fα amplitude spectrum provides additional information that may indicate preferred environmental conditions.
The investigation of aesthetics has primarily been conducted within the visual domain. This is no... more The investigation of aesthetics has primarily been conducted within the visual domain. This is not a surprise, as aesthetics has largely been associated with the perception and appreciation of visual media, such as traditional artworks, photography, and architecture. However, one doesn’t need to look far to realize that aesthetics extends beyond the visual domain. Media such as film and music introduce a unique and equally rich temporally changing visual and auditory experience. Product design, ranging from furniture to clothing, strongly depends on pleasant tactile evaluations. Studies involving the perception of 1/f statistics in vision have been particularly consistent in demonstrating a preference for a 1/f structure resembling that of natural scenes, as well as systematic individual differences across a variety of visual objects. Interestingly, comparable findings have also been reached in the auditory and tactile domains. In this review, we discuss some of the current literatu...
Decades of research have resulted in a detailed understanding of the retinotopic layout of early ... more Decades of research have resulted in a detailed understanding of the retinotopic layout of early visual areas V1 and V2, but a less detailed understanding of V3 and V4. The central ends of these retinotopic maps join together and form the foveal confluence. Using electrophysiology or cytoarchitecture mapping the precise organisation of visual areas in this foveal confluence has proven difficult. Ironically, therefore the most important region of the visual field maps has remained'terra incognita'. We used fMRI with 1.2× 1.2× 1.2 mm ...
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Papers by Branka Spehar