There may be no safe space in the ongoing war, between scholars, about blank characters.[SPACE] The latest salvo is in the form of a published study.[SPACE,SPACE] You can look for yourself at the character spacing in the study itself:
“Are Two Spaces Better Than One? The Effect of Spacing Following Periods and Commas During Reading,” Rebecca L. Johnson, Becky Bui, and Lindsay L. Schmitt, Attention, Perception, and Psychophysics, epub 2018. The authors, at Skidmore College, explain:
“The most recent edition of the American Psychological Association (APA) Manual states that two spaces should follow the punctuation at the end of a sentence. This is in contrast to the one-space requirement from previous editions. However, to date, there has been no empirical support for either convention. In the current study, participants performed (1) a typing task to assess spacing usage and (2) an eye-tracking experiment to assess the effect that punctuation spacing has on reading performance. Although comprehension was not affected by punctuation spacing, the eye movement record suggested that initial processing of the text was facilitated when periods were followed by two spaces, supporting the change made to the APA Manual.”