The journal article “Parallel visual processes in symmetry perception: Normality and
pathology” addresses the idea of whether or not there is an anatomical basis for symmetry
perception. The researchers examined people whose eyesight varied from normal to impaired
by various maladies.
In the introduction, the “Euclidean” symmetries of translation, rotation, reflection, and glide reflection are identified. Such verbiage is paralleled to the transformations of point, vertical, horizontal, and identity discussed in class. Some ambiguity lies in the difference between the article’s ideas of transformation versus reflection. This may simply be different words for horizontal and vertical, which both appear to be reflections about various axes. The author is assuming that the reader is well-informed about symmetry concepts, but still manages to lose the reader somewhat in his language.
It is stated that the mechanisms for symmetry detection “do not require attention and that they work in parallel at different locations of the visual field” (360). Such an idea makes sense, as people are often aware of the concept of symmetry but so not overtly seek it out in their everyday visual processing. Symmetry is suggested to be “preattentive,” which makes sense as some of the actual biological process for which people detect symmetry do not involve them purposefully seeking out symmetrical images. For example, it has pretty much become common knowledge that babies favor symmetrical faces over asymmetrical ones; further, it is often purported that beauty overall has a symmetrical basis. In these instances acknowledging that symmetry is contributing to the detection of a favorable face would almost retract from the perceived beauty. Thus, it follows logically that the eye has some biological mechanism for detecting symmetry.
The most interesting part of the paper came when the tests of symmetry detection around various vertical axes were discussed. Apparently, the eye most accurately detects symmetries at the main diagonals of 45 and 135 degrees. The researcher found “better performance at the main diagonals, with gradually decreasing performance when the axis of symmetry was turned away from the main diagonals” (364). However, this was not conclusive proof that symmetry detection is anatomically determined. Other psychological factors and the frequency of how many times an image is shown to a subject can affect how accurately symmetry is identified. The whole section on retinitis pigmentosa gives inconclusive results at best. The author even states that the data obtained is used both my proponents and opponents of the theory that symmetry detection has an anatomical basis.
Aside from the initial introduction of the various translations, the article did not address anything that has been discussed in class. As far as the translations are concerned, the author ultimately concludes that the eye can accurately detect them, but that detection is more complex than the factors anatomy and the physiological system. It would be interesting then, to delve into what psychological or other factors can play a part in the detection of symmetry. If it is an automatic, preattentive skill, then evolutionarily it must have brought humans some benefit causing people to have such an adaptation. Research could be done with different species’ physiological systems to find if they have similar adaptations. All of their detections would be preattentive, so the human factor of knowledgably searching for symmetry would be eliminated. Overall, the article brings up interesting topics but does little to ultimately resolve them.
