sentences:  Weaver reported that leftward regressions run from 7% to a substantial 23% of all saccades in the sight-reading of keyboard music.Goolsby and Smith reported significant levels of leftward refixation across all skill-levels in the sight-reading of melodies.Looking at the same information more than once is, "prima facie", a costly behaviour that must be weighed against the need to keep pace with the tempo of the music.