The full sentence is: "Previous well-cited work establishes human perceptual system thresholds, but these studies were conducted on now outdated equipment"
Should "now outdated" be changed to "now-outdated"?
Chicago Manual of Style, in its incredibly helpful hyphenation table, says that a phrasal adjective made up of an adverb not ending in -ly + a participle should be hyphenated when it comes before the noun. That makes the case for the hyphen, and while there are some conceivable reasons to leave it open, I don't think hyphenating here would be incorrect--unless there's a specific rule to "now" that I haven't found out about yet. (Chicago notes that several words, such as "less," are usually left open even before a noun.)