Remark on the Isospin Mass Differences

The isospin splittings of the ${\mathrm{\textonehalf{}}}^{+}$ baryon octet are observed empirically to depend upon the (average) sum of charge and hypercharge or equivalently, upon the (average) ${V}_{3}=\ensuremath{-}\frac{1}{2}(Q+Y)$ spin component. We construct a simple quark model compatible with this observation and then use this model to predict the ${\frac{3}{2}}^{+}$ decuplet isospin splittings. One obtains different decuplet predictions from the standard approach, enabling one eventually to test whether or not the baryon regularity is accidental. If nonaccidental, then support is given to recent conjectures that isospin splittings may be partially nonelectromagnetic.