Photometric observations of a wide and a narrow outburst of the dwarf nova SS Cygni are used to test the hypothesis that the same mechanism is responsible for the wide outbursts of U Gem stars and the wide outbursts of SU UMa stars. A search for modulations at or near the orbital period of the SS Cygni outbursts was conducted, showing no modulations to a limit of about 0.05 mag. The results are interpreted by Whitehurst's (1984) tidal superhump model which suggests that SU UMa and U Gem outbursts are manifestations of the same basic driving mechanism, but that the presence of superhumps is limited to extreme mass-ratio systems.