“…There are many findings that support the conditioning analysis of tolerance (see reviews by Dworkin, 1993;Ramsay & Woods, 1997;Siegel, in press;Siegel & Allan, 1998). There also are contrary findings (e.g., Bardo & Hughes, 1979;Goudie & Griffiths, 1984;Kesner & Cook, 1983;LaHoste, Olson, Olson, & Kastin, 1980;Tiffany & Maude-Griffin, 1988). The purpose of these experiments was to investigate a basis for the discrepant findings.…”