Human hair color account for all possible shades of brown, blond, or red (for example, platinum blond versus dark blond/light brown), nor does it explain why hair color sometimes darkens as a person ages. Several gene pairs control the light versus dark hair color in a cumulative effect. A person's genotype for a multifactorial trait can interact with the environment to produce varying phenotypes (see quantitative trait locus). Natural hair color can be brown, blond, black, red, or white; all natural hair colors including grey, white and lightest blond, are shades of brown. The Fischer–Saller scale, named after Eugen Fischer and , is
Spann-Fischer Codependency Scale Spann-Fischer Codependency Scale The Spann-Fischer Codependency Scale is a 16-item self-report instrument used to define and measure co-dependency in order to operationalize it as a personality disorder. Individual items are rated on a 6-point Likert scale, and then summed with two reversed items to describe co-dependency on a scale from a high of 96 to a low of 16. Scores on the codependency scale distinguished known groups; furthermore, scores correlated as expected with intrapersonal measures as well as interpersonal perceptions of parenting in the family of origin. Its creators are Judith L. Fischer PhD and Lynda Spann MS, both from