In a written statement, the certificated flight instructor (CFI) reported that the purpose of the flight was for him to conduct an aerobatic lesson with the airline transport pilot (ATP) in a tail wheel-equipped airplane. After performing air work, the pilots returned back to the airport and the ATP decided to try touch-and-go practice takeoffs and landings. The first three landings were uneventful and he had planned for the fourth to be a full stop with the airplane configured for a three-point landing. Following a normal approach and touchdown, the airplane was on the landing roll when it suddenly turned to the left 30 degrees relative to the runway centerline. Both pilots applied full right rudder, but the airplane continued the left turn. The CFI attempted to apply light right brake pressure but the airplane exited the left side of the runway and ground looped. The airplane came to a rest facing approximately 270 degrees from the runway centerline; during the accident sequence, damage was incurred to the right wing tip and left aileron. The pilots both reported that there were no pre impact mechanical failures or malfunctions with the airframe or engine.