Using non-specific dopaminergic agents, Meck (1983, 1986) and his colleagues have repeatedly demonstrated manipulations of the internal clock mechanism, while showing no other changes to the psychophysical function (DL & WF). The current study used analyses and procedures similar to those of Meck (1983) and investigated the internal clock mechanism with the specific D2 agonist, quinpirole. Two groups were trained with saline and tested with quinpirole (0.08 mg/kg). One group was naive to the drug prior to testing (DN), while the other had previous drug exposure (DE). A third group (DT) was trained with quinpirole, and tested with saline. The DN and DE groups revealed no differences in acquisition, no predicted shift in the point of subjective equality (PSE), and changes in the DL and WF, when compared over phase. The DT group acquired the task more slowly and to a lower criterion, and no differences were found in the PSE, DL, or WF, over phase. The data presented here do not support dopaminergic control over the clock component as represented in the Internal Clock Model (Church, 1989). Results are consistent with other research (Lejeune et al., 1995; Rapp & Robbins, 1976; Santi et al., 1995; Stubbs & Thomas, 1974) in suggesting that dopaminergic control of the internal clock is more complex than was once thought
