The average of a color distribution has special significance for color coding (e.g., to estimate the illuminant) but how it depends on the visual representation (e.g., perceptual versus cone-opponent) or nonlinearities (e.g., categorical coding) is unknown. We measured the perceived average of two colors shown alternated in spatial arrays. Observers adjusted the components until the average equaled a specified reference hue. Matches for red, blue-red, or yellow-green were consistent with the arithmetic mean chromaticity, while blue-green settings deviated toward blue. The settings show little evidence for categorical coding, and cannot be predicted from the scaled appearances of the individual components.

Current laboratory monitoring may not be optimal.A retrospective chart review was performed on thelaboratory results of 246 patients who were treatedwith isotretinoin for acne over a 9-year period. Testsobtained were CBC, lipid panel, AST, ALT, CK, GGT,and C-reactive protein. Thirty-five patients had anelevated AST and 35 of these had an elevated CK; 32had an elevated ALT and 11 of these had an elevatedCK. Thirteen patients had an elevated GGT; in 5 thiswas the only abnormality, whereas 8 had a GGTelevation accompanied by an elevated AST or ALT.Two had an elevated GGT and an elevated CK withnormal AST and ALT. Fifty-two patients had a singleepisode of elevated CK, of which 22 were female.However, 57 had multiple CK elevations and only onewas female. Thirty-five patients had CK elevations <2 times normal; 38 had levels between 2 and 3 timesnormal, 18 had levels between 3 and 4 times normal,and 18 had levels greater than 4 times normal. Wesuggest that ALT and AST are not useful for monitoringisotretinoin therapy and that GGT and CK may be ofgreater value in managing patients.

This music score was submitted for the Kaleidoscope 2020 Call for Scores, an open access collaboration with the UCLA Music Library.

Response to Commentaries.