“…To address this, some researchers have experimentally manipulated efficacy, often by varying performance comparison groups (Feltz & Riessinger, 1990;Weinberg, Gould, Yukelson, & Jackson, 198 1 ;Weinberg, Gould, & Jackson, 1979;Wilkes & Summers, 1984). However, in such research, which typically involves lab experiments, external validity becomes problematic, leading to concern about the generalizability of the findings outside the laboratory setting.…”