Came here wanting to cite a study advocating use of lowercase letters (as I've been told), but a quick search turned up this: https://www.ncbi.nlm.nih.gov/pmc/

Came here wanting to cite a study advocating use of lowercase letters (as I've been told), but a quick search turned up this: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2016788/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2016788/ "Our finding that size thresholds for upper-case text were lower than those for lower-case text in Experiment 1 are not surprising, and corroborate the findings of (M. Tinker, 1963) that at great viewing distance (as simulated by small visual size), upper-case text is more legible, even in a font with a relatively large x-height, which might be expected to minimize upper- and lower-case differences. Other fonts, which typically have smaller x-heights, might be expected to show upper-case text to have even greater relative legibility. Contrary to Tinker’s findings, and the conventional wisdom, is the result that upper-case text is more legible in terms of reading speed, for readers with reduced acuity due to visual impairment, and in normally-sighted readers when text is visually small. This result may have practical significance as well; it suggests that, apart from economic considerations of how much space a given sample of text occupies, letter size determines legibility for low vision readers and for those viewing visually small text; and when point size is fixed, upper-case text is simply more legible, albeit less aesthetically appealing, than lower-case."