Preparatory Experiments Regarding Human Brain Perception and Reasoning of Image Complexity for Synthetic Color Fractal and Natural Texture Images via EEG

Abstract

Texture plays an important role in computer vision in expressing the characteristics of a surface. Texture complexity evaluation is important for relying not only on the mathematical properties of the digital image, but also on human perception. Human subjective perception verbally expressed is relative in time, since it can be influenced by a variety of internal or external factors, such as: Mood, tiredness, stress, noise surroundings, and so on, while closely capturing the thought processes would be more straightforward to human reasoning and perception. With the long-term goal of designing more reliable measures of perception which relate to the internal human neural processes taking place when an image is perceived, we firstly performed an electroencephalography experiment with eight healthy participants during color textural perception of natural and fractal images followed by reasoning on their complexity degree, against single color reference images. Aiming at more practical applications for easy use, we tested this entire setting with a WiFi 6 channels electroencephalography (EEG) system. The EEG responses are investigated in the temporal, spectral and spatial domains in order to assess human texture complexity perception, in comparison with both textural types. As an objective reference, the properties of the color textural images are expressed by two common image complexity metrics: Color entropy and color fractal dimension. We observed in the temporal domain, higher Event Related Potentials (ERPs) for fractal image perception, followed by the natural and one color images perception. We report good discriminations between perceptions in the parietal area over time and differences in the temporal area regarding the frequency domain, having good classification performance.

Color Texture Image Complexity—EEG-Sensed Human Brain Perception vs. Computed Measures

“…The present work extends the work from [48], where we have compared the image analysis complexity assessment and brain responses between color natural and color synthetic fractal textures with a one-color image being used as reference, by means of an experimental EEG study. The neural responses assessment tends to suggest that fractal images require more complex thought processes with higher complexity in reasoning, even though the color fractal dimension (CFD) indicates no complexity difference between the fractal and natural image groups, also being supported by subjects evaluation who equally expressed the fractal and natural images as more complex in structural form.…”

“…In this section, we briefly recall the experiment that we performed, which is detailed in the first part of the study [48].…”

“…The power spectrum was computed from 3 to 40 Hz, on the trial interval (0-1350 ms), based on the Fourier transform with Kaiser window and the logarithmic spectral power is presented as 10 • log 10 (power). For further details on signal processing, please see [48].…”

“…In addition to the experiment and study presented our previous work [48], we also conducted a subjective experiment after the EEG measurements. This complementary experiment aimed at providing details on the complexity perception of each participant.…”

Impact of Visual Design Elements and Principles in Human Electroencephalogram Brain Activity Assessed with Spectral Methods and Convolutional Neural Networks

“…The perception of colour is an important cognitive feature of the human brain and is a powerful descriptor that considerably expands our ability to characterize and distinguish objects by facilitating interactions with a dynamic environment [ 43 ]. Some of the most recent studies that have addressed the interactions of colour and human perception through EEG are the response of a human visual system to continuous colour variation [ 44 ], human brain perception and reasoning of image complexity for synthetic colour fractal and natural texture images via EEG [ 45 ], or neuromarketing studies based on the study of colour perception and the application of EEG power for the prediction and interpretation of consumer decision-making [ 46 ], and so forth.…”