Skin reflectance, iris pigmentation and information processing in children

Eye Color as an Indicator of Behavior: Revisiting Worthy and Scott

Phenotypic eye color has been suggested as an indicator of genetic predisposition toward certain behaviors both in humans and in animals. Previous research has yielded mixed results. Phototaxic and ethological behaviors were examined in 14 different strains of Drosophila melanogaster. No significant correlation between phenotypic eye coloration and behavior was found, although significant genotypical behavioral differences were noted even among subjects with similar eye colors. An analysis of cellular defects associated with eye color in D. melanogaster pointed to significant behavioral differences among cell-defect groups, indicating that the cell defect which causes eye color, rather than eye color itself, may serve as a crude indicator of behavior.

Melanin: the organizing molecule

The hypothesis is advanced that (neuro)melanin (in conjunction with other pigment molecules such as the isopentenoids) functions as the major organizational molecule in living systems. Melanin is depicted as an organizational "trigger" capable of using established properties such as photon-(electron)-phonon conversions, free radical-redox mechanisms, ion exchange mechanisms, and semiconductive switching capabilities to direct energy to strategic molecular systems and sensitive hierarchies of protein enzyme cascades. Melanin is held capable of regulating a wide range of molecular interactions and metabolic processes primarily through its effective control of diverse covalent modifications. To support the hypothesis, established and proposed properties of melanin are reviewed (including the possibility that (neuro)melanin is capable of self-synthesis). Two "melanocentric systems"--key molecular systems in which melanin plays a central if not controlling role--are examined: 1) the melanin-purine-pteridine (covalent modification) system and 2) the APUD (or diffuse neuroendocrine) system. Melanin's role in embryological organization and tissue repair/regeneration via sustained or direct current is considered in addition to its possible control of the major homeostatic regulatory systems--autonomic, neuroendocrine, and immunological.