Mona Lisa is always happy – and only sometimes sad

Liaci, Emanuela; Fischer, Andreas; Heinrichs, Markus; Elst, Ludger Tebartz van; Kornmeier, Jürgen

doi:10.1038/srep43511

Cited by 12 publications

(17 citation statements)

References 46 publications

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“…Although somewhat yellowed, the faint blue haze in the background was inspired by the isoprene-derived blue haze in the hills of the Tuscan countryside, as recorded in Leonardo’s notebooks. For comparison, a higher-resolution version of this painting is available from ref ( 547 ).…”

Section: Isoprenoid Diphosphate Lyasesmentioning

confidence: 99%

Structural and Chemical Biology of Terpenoid Cyclases

2017

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The year 2017 marks the twentieth anniversary of terpenoid cyclase structural biology: a trio of terpenoid cyclase structures reported together in 1997 were the first to set the foundation for understanding the enzymes largely responsible for the exquisite chemodiversity of more than 80000 terpenoid natural products. Terpenoid cyclases catalyze the most complex chemical reactions in biology, in that more than half of the substrate carbon atoms undergo changes in bonding and hybridization during a single enzyme-catalyzed cyclization reaction. The past two decades have witnessed structural, functional, and computational studies illuminating the modes of substrate activation that initiate the cyclization cascade, the management and manipulation of high-energy carbocation intermediates that propagate the cyclization cascade, and the chemical strategies that terminate the cyclization cascade. The role of the terpenoid cyclase as a template for catalysis is paramount to its function, and protein engineering can be used to reprogram the cyclization cascade to generate alternative and commercially important products. Here, I review key advances in terpenoid cyclase structural and chemical biology, focusing mainly on terpenoid cyclases and related prenyltransferases for which X-ray crystal structures have informed and advanced our understanding of enzyme structure and function.

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Section: Isoprenoid Diphosphate Lyasesmentioning

confidence: 99%

Structural and Chemical Biology of Terpenoid Cyclases

2017

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“…Further, the Necker cube is a “physically ambiguous reference stimulus”, in the sense that all possible interpretations are physically equally plausible. In contrast, our recent evidence suggests that in the case of Mona Lisa no such clearly defined physically ambiguous reference stimulus exists [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

“…Our perceptual system needs to disambiguate and interpret the available sensory information in order to construct stable and reliable percepts. Ambiguity occurs in different sensory modalities (e.g., [ 2 – 4 ]) and at different processing levels, reaching from low-level figure-ground segregation (e.g., [ 5 ]) or depth processing (e.g., [ 6 ]), over motion integration (e.g., [ 7 , 8 ]) to the emotional content of faces (e.g., [ 9 ]) or semantic and linguistic ambiguities [ 10 ]. Ambiguities in perception, action, and communication can be the source of misunderstandings and conflicts.…”

Section: Introductionmentioning

confidence: 99%

“…Mona Lisa’s emotional expression has been acknowledged worldwide for being enigmatic, offering a persistent ambiguity of a happy face at one moment, fading towards a melancholic expression a moment later [ 35 , 36 ]. Similar to the a priori perspective bias in the case of the Necker cube, we recently identified an a priori happiness-bias (LTM effect), as well as an influence of the immediate perceptual history (STM effect) during perceptual disambiguation of the emotional face content of Mona Lisa variants [ 9 ]. In addition, several studies demonstrated priming and adaptation in the perception of emotional face contents [ 28 , 37 – 46 ].…”

Section: Introductionmentioning

confidence: 99%

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Positive and negative hysteresis effects for the perception of geometric and emotional ambiguities

et al. 2018

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AimThe present study utilizes perceptual hysteresis effects to compare the ambiguity of Mona Lisa’s emotional face expression (high-level ambiguity) and of geometric cube stimuli (low-level ambiguity).MethodsIn two experiments we presented series of nine Mona Lisa variants and nine cube variants. Stimulus ambiguity was manipulated by changing Mona Lisa’s mouth curvature (Exp. 1) and the cubes’ back-layer luminance (Exp. 2). Each experiment consisted of three conditions, two with opposite stimulus presentation sequences with increasing and decreasing degrees of ambiguity, respectively, and a third condition with a random presentation sequence. Participants indicated happy or sad face percepts (Exp. 1) and alternative 3D cube percepts (Exp. 2) by key presses. We studied the influences of a priori perceptual biases (long-term memory) and presentation order (short-term memory) on perception.ResultsPerception followed sigmoidal functions of the stimulus ambiguity morphing parameters. The morphing parameter for the functions’ inflection points depended strongly on stimulus presentation order with similar effect sizes but different signs for the two stimulus types (positive hysteresis / priming for the cubes; negative hysteresis / adaptation for Mona Lisa). In the random conditions, the inflection points were located in the middle between those from the two directional conditions for the Mona Lisa stimuli. For the cube stimuli, they were superimposed on one sigmoidal function for the ordered condition.DiscussionThe hysteresis effects reflect the influence of short-term memory during the perceptual disambiguation of ambiguous sensory information. The effects for the two stimulus types are of similar size, explaining up to 34% of the perceptual variance introduced by the paradigm. We explain the qualitative difference between positive and negative hysteresis with adaptation for Mona Lisa and with priming for the cubes. In addition, the hysteresis paradigm allows a quantitative determination of the impact of adaptation and priming during the resolution of perceptual ambiguities. The asymmetric shifts of inflection points in the case of the cube stimuli is likely due to an a priori perceptual bias, reflecting an influence of long-term memory. Whether corresponding influences also exist for the Mona Lisa variants is so far unclear.

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“…How a face looks in a painting or an advertisement can dramatically influence what we feel about them and what emotions are elicited. Studies are still being made on the face of the Mona Lisa and the emotions that her face conveys [17]. Previous works have proved that when looking at scenes containing human faces, observers tend to rapidly focus on the faces [18], even if faces do not occupy the most part of the scene.…”

Section: Introductionmentioning

confidence: 99%

Evolutionary Computation for Modelling Social Traits in Realistic Looking Synthetic Faces

et al. 2018

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Human faces play a central role in our lives. Thanks to our behavioural capacity to perceive faces, how a face looks in a painting, a movie, or an advertisement can dramatically influence what we feel about them and what emotions are elicited. Facial information is processed by our brain in such a way that we immediately make judgements like attractiveness or masculinity or interpret personality traits or moods of other people. Due to the importance of appearance-driven judgements of faces, this has become a major focus not only for psychological research, but for neuroscientists, artists, engineers, and software developers. New technologies are now able to create realistic looking synthetic faces that are used in arts, online activities, advertisement, or movies. However, there is not a method to generate virtual faces that convey the desired sensations to the observers. In this work, we present a genetic algorithm based procedure to create realistic faces combining facial features in the adequate relative positions. A model of how observers will perceive a face based on its features’ appearances and relative positions was developed and used as the fitness function of the algorithm. The model is able to predict 15 facial social traits related to aesthetic, moods, and personality. The proposed procedure was validated comparing its results with the opinion of human observers. This procedure is useful not only for creating characters with artistic purposes, but also for online activities, advertising, surgery, or criminology.

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Mona Lisa is always happy – and only sometimes sad

Cited by 12 publications

References 46 publications

Structural and Chemical Biology of Terpenoid Cyclases

Structural and Chemical Biology of Terpenoid Cyclases

Positive and negative hysteresis effects for the perception of geometric and emotional ambiguities

Evolutionary Computation for Modelling Social Traits in Realistic Looking Synthetic Faces

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