  Galaxy interactions are studied in terms of the starburst-Seyfert connection.
The starburst requires a high rate of gas supply. Since the efficiency for
supplying the gas is high in a galaxy interaction, although the companion is
not necessarily discernible, Seyfert galaxies with circumnuclear starbursts are
expected to be interacting. Since the large amounts of circumnuclear gas and
dust obscure the broad-line region, they are expected to be observed as Seyfert
2. The active galactic nucleus itself does not require a high rate of gas
supply. Seyfert galaxies without circumnuclear starbursts are not necessarily
expected to be interacting even at the highest luminosities. They are not
necessarily expected to evolve from Seyfert galaxies with circumnuclear
starbursts. We derive these and other theoretical expectations and confirm them
with statistics on observational data of magnitude-limited samples of Seyfert
galaxies.
