“…Studies of frequency discrimination in a nonspeech context, although numerous, have yielded contradictory information, with successes reported by Kasatkin and Levikova (1935), Bronshtein et al (1958), Birns et al (1965), and Bronshtein and Petrova (1967), failures by Goodman, Appleby, Scott, & Ireland (1964), Keen (1964), and Leventhal and Lipsitt (1964) and ambigious results by Bridger (1961). The variety of dependent measures employed in these studies makes comparison difficult, if not impossible.…”