Art and Vision
Why must visual stimuli be so poor?
Striking illustrations find their place in popular books on visual perception. However, the stimuli used for acquiring psychophysical results are usually devoid of visual interest, e.g., (i) strictly minimal stimuli with a small number of dots or segments (ii) sandpaper-like random dot stereograms (iii) horizontal or vertical gratings (iv) figures with Gabor patches. There are hidden, debatable assumptions underlying the design of these stimuli, for instance : (i) The brain does not need a rich environment to appreciate geometrical relationships. (ii) The brain works on a Cartesian x-y array of dots (or neurons) and stereo depth is merely computing a z-coordinate. (iii) Electro-physiology tells us all that really matters for the brain. (iv) illusory effects in complex stimuli merely capture pathological functioning modes of the brain. I will present a selection of illustrations from my popular science or academic publications that, in my opinion, are a good antidote to classical statements derived from psychophysical work on poor stimuli. Paradoxically, it might be that some of the psychophysicist's preferred stimuli are ideal ones for making the brain work in pathological ways.
Color, Music, and Emotion
Stephen Palmer, Karen Schloss and Thomas Langlois
Are color and music systematically related for non-synesthetic people? Forty-eight participants picked the 5 colors that went best (and later the 5 colors that went worst) from an array of 37 colors for each of 18 brief samples of classical orchestral music. The music varied in composer (Bach/Mozart/Brahms), tempo (slow/medium/fast), and mode (major/minor). Participants also rated each musical selection and each color for its emotional associations (happy-sad, lively-dreary, strong-weak, angry calm). Faster music and major mode were associated with lighter, more saturated, yellower colors, whereas slower music and minor mode were associated with darker, desaturated, bluer colors. More-controlled single-line piano melodies by Mozart produced better articulated color-music relations, but similar results occurred for 34 different kinds of popular and world music. Strong evidence for emotional mediation comes from extremely high correlations (.90-.98) between the music and the colors chosen to go with them (e.g., happy colors go with happy music and dreary colors go with dreary music). Analogous effects were obtained when people picked the colors that went best (and worst) with emotional faces (happy-sad and angry-calm) and when they picked the emotional faces that went best (and worst) with the music. Emotion mediates color-music associations.
ERP correlates of visual symmetry perception
Alexis Makin, Moon Wilton, Anna Pecchinenda and Marco Bertamini
The psychological response to visual symmetry has been studied for over 100 years. We conducted two EEG studies exploring neural responses to different types of symmetry. In Study 1, we contrasted three types of rigid transformation (reflection, rotation and translation) with matched random patterns. We found that ERPs amplitude was more negative for the regular patterns than the random patterns from around 250 ms to the end of the trial. This component is known as the Sustained Posterior Negativity (SSN), and interestingly, it did not differ between regularity types. In Study 2, different groups of participants actively discriminated between reflection and random patterns, or between rotation and random patterns. Reflectional symmetry produced the SSN, and source localization techniques identified generators in the extrastriate visual cortex. Rotational symmetry produced an unexpected modulation of early P1 and N1 components. Finally, we analysed the EEG signal in the time-frequency domain, and found that all patterns were associated with desynchronization in the upper alpha frequency band, indicating cortical excitation. Desynchronization was more pronounced over the right posterior regions in some experiments. We conclude that psychophysical differences between different types of visual symmetry map systematically onto EEG metrics, but only under active classification conditions.
Neural correlates of perceptual pleasure and “Aha” experiences triggered by perceptual flips in ambiguous images
Jasmina Stevanov, Maiko Uesaki, Hiroshi Ashida, Thomas Carlson, Gerald Cupchik and Akiyoshi Kitaoka
Parahippocampal cortex has previously been implicated in perceptual pleasure. Highly preferred and “richly interpretable” images are associated with greater activity in PPA, an area with a high density of μ-opioid receptors (Yue et al, 2007, NeuroReport, 18, 525-529). We hypothesized that the positive emotional experience associated with the "Aha" moment would increase activity in PPA. We used fMRI to measure brain activity while participants viewed ambiguous paintings of Ocampo, Arcimboldo, Del-Prete and Utagawa, each of which has distinct local and global interpretations. In each trial, stimuli were slowly demagnified starting from local details and ending with the global view. Subjects pressed a button the moment they recognized the global figure (e.g. face). This gradual deployment of the stimulus allowed us to uncouple activity associated with the stimulus from that associated with the “Aha” experience. Different patterns of brain activity were observed in occipito-temporal lobe, visual areas and a variety of other brain regions associated with aesthetic responses to visual art. Critically, we found activity in PPA was associated with the moment of the perceptual “flip”. We suggest that the pleasure associated with the "Aha" experience is reflected in activity in PPA.
Art versus Reality – Contextual framing affects emotional and aesthetic evaluations of artworks and IAPS pictures
Gernot Gerger, David Welleditsch and Helmut Leder
In the perception of art, negative or disturbing contents are sometimes enjoyed. It can be surmised that an aesthetic context produces changes in the emotional and aesthetic experience leading to positive evaluations of emotionally negative stimuli [Leder, et al., 2004, British Journal of Psychology, 95, 489-508]. To test this hypothesis, we manipulated context by framing either an art or reality context while participants evaluated positively or negatively valenced contemporary artworks and non-art IAPS pictures. We measured aesthetic responses by assessing liking, and emotional responses by collecting ratings of joy, anger, disgust, fear, and sorrow as well as recording facial EMG. Negative artworks were indeed rated as more positive (i.e., higher liking and joy ratings) in an art compared to a reality context. Moreover, stronger zygomaticus activations indicated higher positive affective reactions to negative artworks in an art compared to a reality context. For IAPS pictures, context influenced ratings of joy in a similar way as in artworks. However, for both stimuli classes, context had no influence on evaluating negative emotions of anger, disgust, fear and sorrow. This study demonstrates that art context enables processes which allow a more positive evaluation of negative stimuli, thus discarding the immediacy of emotions.
Relating subjective with objective measures of complexity in affective environmental scenes and representative paintings
Manuela Marin and Helmut Leder
Visual complexity has been found to be related to subjective measures of preference, pleasantness and beauty. However, previous research does not provide a clear picture about the nature of this relationship, and objective measures of complexity in combination with subjective ratings may help to resolve this issue [Forsythe et al., 2011, British Journal of Psychology, 102, 49-70]. The emotional content of visual stimuli has been neglected in prior studies but is crucial in many everyday contexts and particularly when experiencing visual art. We thus compared the relationship between measures of subjective and objective complexity (four compression formats, Canny edge detection and perimeter detection) in a series of four experiments, each employing either a set of 96 IAPS pictures or 96 representative paintings varying in emotional contents (pleasantness and arousal) and complexity (low versus high). Ratings of familiarity, complexity, pleasantness and arousal were obtained under short (5s) and long (25s) presentation times. Analyses indicate that (1) the patterns of relationships between objective and subjective measures of complexity vary across stimuli sets, whereas (2) the relationships between the four subjective ratings are similar, and that (3) presentation time has a minor effect on these relationships in art perception.
Think global, act local: Do local visual processing biases explain proficiency in observational drawing in non-autistic individuals?
Rebecca Chamberlain, Chris McManus, Howard Riley, Qona Rankin and Nicola Brunswick
Exceptional graphical abilities in autistic savants have been explained by enhanced local visual processing, coupled with an intact global advantage effect under voluntary selective attention (Plaisted, Swettenham & Rees, 1999, Journal of Child Psychology & Psychiatry, 40, 733-742). Furthermore, it has been suggested that non-autistic children who are precocious at drawing exhibit the same local processing hallmarks as their autistic savant peers (Drake, Redash, Coleman, Haimson & Winner, 2010, Journal of Autism and Developmental Disorders, 40, 762-773). Similar effects have been seen in artistic adults whose drawing experience was correlated with reduced holistic processing in face perception tasks (Zhou, Cheng, Zang & Wong, 2011). In an initial study performance on the embedded figures task (EFT), a measure of local visual processing, independently predicted both self-perceived and objectively assessed drawing ability. This finding was examined in a study that probed both local and global visual processing in art students and controls using Navon shape stimuli, the Block Design Task (Shah & Frith, 1993, Journal of Child Psychology & Psychiatry, 34, 1351-1364) and the attention to detail subscale of the Autism Spectrum Quotient (AQ). The results are discussed with reference to perceptual enhancement theories of observational drawing ability.
Simultaneous contrast and depth effects from “true” colors on grey backgrounds: Chevreul’s laws of color and contrast revisited
Birgitta Dresp-Langley and Adam Reeves
Chevreul’s (1839) general laws of "color” and "contrast" predict that colors on achromatic (grey) backgrounds are the least likely to produce mutual interactions affecting our perception, and that the luminance contrast of a color directly determines its likelihood to stand out in depth against the background. We show that colored squares of brighter and darker luminance placed on either side of equiluminant grey backgrounds produce simultaneous contrast effects where assimilation and contrast may occur in one and the same configuration, regardless of color, contrast, or polarity of inducers. Probabilities of no effect, contrast, and assimilation (3AFC between background on left seen as "brighter", "darker", or "same" as on right) were measured. Configurations of red, green, blue, yellow and white (grey) inducers on light and dark grey were presented in random order under conditions of darkadaptation, rodsaturation, and daylight. Adaptation level had no significant effect. Grouping two backgrounds into a single one significantly increased the probability of no effect, suggesting mechanisms which integrate contrast at luminance borders and discount global illumination. Relative depth judgments in terms of probabilities of colored inducers to be perceived as nearer to the observer (3AFC between “left=nearer”, “right=nearer”, or “same”) show that background grouping has no effect on relative depth judgments. These are determined by inducer color and luminance contrast/polarity, producing significantly higher probabilities of brighter colors to be seen as nearer. A statistically significant effect of adaptation level is observed, where response probabilities for no effect are lowest under daylight conditions. This is consistent with observations that relative distance estimates are more accurate on a bright and clear day than on a foggy one, and more reliable on land than under water. Chevreul’s “law of contrast” for depth from color is proven to hold under conditions where local geometric cues to depth are unavailable. FINANCIAL SUPPORT: CNRS-PICS-05971