Sherwin et al. examined the strength of motivation for burrowing substrate in laboratory mice. Despite an increasing cost of gaining access, the mice continued to work to visit the burrowing substrate.Sherwin, C.M., Haug, E., Terkelsen, N. and Vadgama, M., (2004). Studies on the motivation for burrowing by laboratory mice. Applied Animal Behaviour Science, 88: 343-358 In addition, it was shown that it was the performance of burrowing behaviour that was important to the mice, not simply the functional consequences of the behaviour. King and Welsman showed that when bar pressing gave deermice access to sand, they increased their rate of bar pressing as the number of presses to access the sand was increased.King, J.A. and Weisman, R.G., (1964) Sand digging contingent upon bar pressing in deermice (Peomyscus). Animal Behaviour, 12: 446-450
