Complex sentence: Research into control of spending habits across the cycle observed a significant degree of variability with regard to bidding behaviour across the menstrual cycle within both pill users as well as naturally cycling non-pill users.
Split into simpler sentences: Research into control of spending habits across the cycle has produced mixed results. A significant degree of variability with regard to bidding behaviour is observed across the menstrual cycle within both pill users as well as naturally cycling non-pill users.