they say it takes two to tango and it seems that for physical tasks practicing with a partner really does improve performance practice is better with a partner study shows and in another similar experiment with disrupted sleep in mice but involving implanting tumor cells in the mices thigh disrupted sleep could spur cancer growth through immune system effects animal study shows as an infectious disease doctor i felt a little embarrassed that i didnt know the definitive answer to this simple question especially since i repeatedly rebuke my teenage children for not taking a jacket to school or wearing socks and a sweater at home did the cold cause my cold