McKerchar, T. L., Zarcone, T. J., & Fowler, S. C. (2005).
Differential acquisition of lever pressing in inbred and outbred mice:
Comparison of one-lever and two-lever procedures and correlation with
differences in locomotor activity.
Journal of the Experimental Analysis of Behavior, 84, 339-
356.
Recent progress in mouse genetics has led to an increased interest in developing
procedures for assessing mouse behavior, but relatively few of the behavioral
procedures developed involve positively reinforced operant behavior. When
operant methods are used, nose poking, not lever pressing, is the target
response. In the current study differential acquisition of milk-reinforced lever
pressing was observed in five inbred strains (C57BL/6J, DBA/2J, 129X1/SvJ,
C3H/HeJ, and BALB/cJ) and one outbred stock (CD-1) of mice. Regardless of
whether one or two levers (an “operative” and “inoperative” lever) were in the
operant chamber, a concomitant variable-time fixed-ratio schedule of milk
reinforcement established lever pressing in the majority of mice within two 120-
min sessions. Substantial differences in lever pressing were observed across
mice and between procedures. Adding an inoperative lever retarded acquisition in
C57BL/6J, DBA/2J, 129X1/SvJ, and C3H/HeJ mice, but not in CD-1 and BALB/cJ mice.
Locomotor activity was positively correlated with number of lever presses in
both procedures. Analyses of durations of the subcomponents (e.g., time to move
from hopper to lever) of operant behavior revealed further differences among the
six types of mice. Together, the data suggest that appetitively reinforced lever
pressing can be acquired rapidly in mice and that a combination of procedural,
behavioral, and genetic variables contributes to this acquisition.
Key words: behavioral genetics, operant acquisition, one-lever, two-lever,
concomitant schedule, lever press, mice