Dahlia W. Zaidel

Appearance of symmetry, beauty, and health in human faces

Symmetry is an important concept in biology, being related to mate selection strategies, health, and survival of species. In human faces, the relevance of left-right symmetry to attractiveness and health is not well understood. We compared the appearance of facial attractiveness, health, and symmetry in three separate experiments. Participants inspected front views of faces on the computer screen and judged them on a 5-point scale according to their attractiveness in Experiment 1, health in Experiment 2, and symmetry in Experiment 3. We found that symmetry and attractiveness were not strongly related in faces of women or men while health and symmetry were related. There was a significant difference between attractiveness and symmetry judgments but not between health and symmetry judgments. Moreover, there was a significant difference between attractiveness and health. Facial symmetry may be critical for the appearance of health but it does not seem to be critical for the appearance of attractiveness, not surprisingly perhaps because human faces together with the human brain have been shaped by adaptive evolution to be naturally asymmetrical.

She is not a beauty even when she smiles: Possible evolutionary basis for a relationship between facial attractiveness and hemispheric specialization

The asymmetrical status of facial beauty has rarely been investigated. We studied positive facial characteristics, attractiveness and smiling, through the use of left-left and right-right composites of unfamiliar faces of women and men with natural expressions. Results showed that womens right-right composites were judged significantly more attractive than left-left composites while there was no left-right difference in mens composites (Experiment 1). On the other hand, left-left composites were judged to have more pronounced smiling expressions than right-right composites in both womens and mens faces (Experiment 2). The results confirm previous findings for leftward facial expressiveness and show for the first time asymmetry in facial attractiveness and a difference in its manifestation in womens and mens faces. The findings have biological implications for the relationship between the appearance of the sides of the face and hemispheric specialization. The organization of beauty in the human face may have been shaped by evolutionary pressures on facial asymmetries, especially as they pertain to mate selection.

Memory for faces in epileptic children before and after brain surgery

Memory for pairs of unfamiliar childrens faces was investigated in 29 children and adolescents suffering from left (LTLE) or right (RTLE) temporal-lobe epilepsy, before and after temporal-lobe surgery. Both immediate and delayed memory were tested. Before surgery, RTLE subjects performed worse than either LTLE subjects or normal children. After surgery, RTLE subjects improved significantly. Overall (after surgery), there was no significant LTLE-RTLE difference, but on delayed memory, the RTLE group was worse than the LTLE group. The results suggest specialization for facial memory in the right hemisphere of young patients, as in adults, despite early brain damage.

THE FACE, BEAUTY, AND SYMMETRY: PERCEIVING ASYMMETRY IN BEAUTIFUL FACES

The relationship between bilateral facial symmetry and beauty remains to be clarified. Here, straight head-on photographs of “beautiful” faces from the collections of professional modeling agencies were selected. First, beauty ratings were obtained for these faces. Then, the authors created symmetrical left-left and right-right composites of the beautiful faces and asked a new group of subjects to choose the most attractive pair member. “Same” responses were allowed. No difference between the left-left and right-right composites was revealed but significant differences were obtained between “same” and the left-left or right-right. These results show that subjects detected asymmetry in beauty and suggest that very beautiful faces can be functionally asymmetrical.

The alien hand syndrome: classification of forms reported and discussion of a new condition

Abstract.The term “alien hand” refers to a variety of clinical conditions whose common characteristic is the uncontrolled behavior or the feeling of strangeness of one extremity, most commonly the left hand. Acommon classification distinguishes between the posterior or sensory form of the alien hand, and the anterior or motor form of this condition. However, there are inconsistencies, such as the phenomenon of diagonistic dyspraxia, which is largely a motor syndrome despite being more frequently associated with posterior callosal lesions. We discuss critically the existing nomenclature and we also describe a case recently reported by us which does not fit any previously reported condition, termed agonistic dyspraxia. We propose that the cases of alien hand described in the literature can be classified into at least five broad categories: (i) diagonistic dyspraxia and related syndromes, (ii) alien hand, (iii) way-ward hand and related syndromes, (iv) supernumerary hands and (v) agonistic dyspraxia.

Art and brain: insights from neuropsychology, biology and evolution

Art is a uniquely human activity associated fundamentally with symbolic and abstract cognition. Its practice in human societies throughout the world, coupled with seeming non‐functionality, has led to three major brain theories of art. (1) The localized brain regions and pathways theory links art to multiple neural regions. (2) The display of art and its aesthetics theory is tied to the biological motivation of courtship signals and mate selection strategies in animals. (3) The evolutionary theory links the symbolic nature of art to critical pivotal brain changes in Homo sapiens supporting increased development of language and hierarchical social grouping. Collectively, these theories point to art as a multi‐process cognition dependent on diverse brain regions and on redundancy in art‐related functional representation.

Neuroaesthetics: The Cognitive Neuroscience of Aesthetic Experience.

The field of neuroaesthetics has gained in popularity in recent years but also attracted criticism from the perspectives both of the humanities and the sciences. In an effort to consolidate research in the field, we characterize neuroaesthetics as the cognitive neuroscience of aesthetic experience, drawing on long traditions of research in empirical aesthetics on the one hand and cognitive neuroscience on the other. We clarify the aims and scope of the field, identifying relations among neuroscientific investigations of aesthetics, beauty, and art. The approach we advocate takes as its object of study a wide spectrum of aesthetic experiences, resulting from interactions of individuals, sensory stimuli, and context. Drawing on its parent fields, a cognitive neuroscience of aesthetics would investigate the complex cognitive processes and functional networks of brain regions involved in those experiences without placing a value on them. Thus, the cognitive neuroscientific approach may develop in a way that is mutually complementary to approaches in the humanities.The field of neuroaesthetics has gained in popularity in recent years but also attracted criticism from the perspectives both of the humanities and the sciences. In an effort to consolidate research in the field, we characterize neuroaesthetics as the cognitive neuroscience of aesthetic experience, drawing on long traditions of research in empirical aesthetics on the one hand and cognitive neuroscience on the other. We clarify the aims and scope of the field, identifying relations among neuroscientific investigations of aesthetics, beauty, and art. The approach we advocate takes as its object of study a wide spectrum of aesthetic experiences, resulting from interactions of individuals, sensory stimuli, and context. Drawing on its parent fields, a cognitive neuroscience of aesthetics would investigate the complex cognitive processes and functional networks of brain regions involved in those experiences without placing a value on them. Thus, the cognitive neuroscientific approach may develop in a way that is mutually complementary to approaches in the humanities.

Hemispheric asymmetry in long-term semantic relationships

Abstract Latencies in a category membership decision task were used to investigate hemispheric organisation of concepts in long-term semantic memory (LTSM). The experiment used the hemi-field technique to lateralise pictures representing high versus low typicality instances of pre-designated concepts to the right and left hemispheres. The results demonstrated hemispheric asymmetries in storage/retrieval of category members. In the right hemisphere, latencies were shorter for high than for low typicality members, consistent with previously reported prototypicality effects in free vision (Rosch, 1975), whereas for the left hemisphere, no dissociation was found. The results are interpreted in terms of two distinct conceptual organisations in the brain, one specialised in the right hemisphere and based on family resemblances/prototypicality, and one specialised in the left hemisphere and possibly based on necessary and sufficient/logical definitions. The view adopted is that typicality effects are not obligat...

Left and right intelligence: case studies of Raven's progressive matrices following brain bisection and hemidecortication.

Abstract Each hemisphere of two commissurotomy and two hemispherectomy patients was tested separately on the book form of Ravens Standard Progressive Matrice test (RSPM) and on the book, board and tactile forms of Ravens Coloured Progressive Matrices test (RCPM). The two patients who had undergone complete cerebral commissurotomy were tested unilaterally with the aid of a contact lens technique which permits free unilateral ocular scanning and visual guidance. The two other patients had undergone dominant (right) and non-dominant (left) hemispherectomy for post-infantile lesions and were tested in free vision. IQ estimates for the left hemispheres based on RSPM scores ranged from 74 to 103 (mean 87) and right hemisphere IQ estimates ranged from 74 to 93 (mean 83). Whereas a small and insignificant trend for left hemisphere dominance was observed on the RSPM, an insignificant trend of right hemisphere superiority appeared on the RCPM. The same trend of right hemisphere advantage had been observed on a tactile-visual modification of the RCPM ( D. Zaidel and Sperry, 1973 ). Thus, the suggested laterality pattern seems to be modality nonspecific. In contrast to the small difference in lateral preference for each of the two tests as a whole, the individual problem sets in both tests yielded different laterality indices. Further, bigger laterality effects were observed on more difficult items. The right hemispheres also seemed more labile and less sensitive to item difficulty than either the corresponding left hemispheres or normal subjects with comparable scores. Instructions to use an overt trial-and-error solution method with the board form of the RCPM resulted in a change of strategy in both hemispheres. But only the left hemisphere of patient N.G., who did not have a ceiling effect, seemed to benefit from the opportunity for error correction to become superior on this version of the RCPM. The right hemisphere seems unable to utilize partial information as if its solution strategy is non-constructive. Neither the isolated nor the disconnected hemisphere has the dramatic focal deficits, such as unilateral neglect of space or dramatically reduced RPM scores, which often accompany unilateral cerebral insult. To the extent that RSPM measures general intelligence (“g”), our data suggest that “g” is bilaterally represented though in unequal amounts for different parts of the test. Thus, the data better support the primary abilities model of intelligence with localized and neurologically dissociable cerebral organization, than they support a hierarchical model incorporating a concept of “g” that enters into all intellectual functions and is homogeneously represented in the cerebral cortex. It is suggested that “g” may contain at least two independent factors, 9 L and g R .

Brain intersections of aesthetics and morals: perspectives from biology, neuroscience, and evolution.

For centuries, only philosophers debated the relationship between aesthetics and morality. Recently, with advances in neuroscience, the debate has moved to include the brain and an evolved neural underpinning linking aesthetic reactions and moral judgment. Biological survival emphasizes mate selection strategies, and the ritual displays have been linked to human aesthetics in the arts, in faces, and in various daily decision making. In parallel, cultural human practices have evolved to emphasize altruism and morality. This article explores the biological background and discusses the neuroscientific evidence for shared brain pathways for aesthetics and morals.