May, M. E., & Kennedy, C. H. (2009).
Aggression as positive reinforcement in mice under various ratio- and
time-based reinforcement schedules.
Journal of the Experimental Analysis of Behavior, 91, 185-196.
There is evidence suggesting aggression may be a positive reinforcer in many species. However, only a
few studies have examined the characteristics of aggression as a positive reinforcer in mice. Four types of
reinforcement schedules were examined in the current experiment using male Swiss CFW albino mice
in a resident-intruder model of aggression as a positive reinforcer. A nose poke response on an operant
conditioning panel was reinforced under fixed-ratio (FR 8), fixed-interval (FI 5-min), progressive ratio
(PR 2), or differential reinforcement of low rate behavior reinforcement schedules (DRL 40-s and DRL
80-s). In the FR conditions, nose pokes were maintained by aggression and extinguished when the
aggression contingency was removed. There were long postreinforcement pauses followed by bursts of
responses with short interresponse times (IRTs). In the FI conditions, nose pokes were maintained by
aggression, occurred more frequently as the interval elapsed, and extinguished when the contingency
was removed. In the PR conditions, nose pokes were maintained by aggression, postreinforcement
pauses increased as the ratio requirement increased, and responding was extinguished when the
aggression contingency was removed. In the DRL conditions, the nose poke rate decreased, while the
proportional distributions of IRTs and postreinforcement pauses shifted toward longer durations as the
DRL interval increased. However, most responses occurred before the minimum IRT interval elapsed,
suggesting weak temporal control of behavior. Overall, the findings suggest aggression can be a positive
reinforcer for nose poke responses in mice on ratio- and time-based reinforcement schedules.
Key words: CFW mice, aggression, positive reinforcement, progressive-ratio, fixed-ratio, fixed-interval,
differential reinforcement of low rate, nose poke