Peering into the Dynamics of Social Interactions: Measuring Play Fighting in Rats

Summary

Play fighting in the rat involves attack and defense of the nape of the neck, which if contacted, is gently nuzzled with the snout. Because the movements of one animal are countered by the actions of its partner, play fighting is a complex, dynamic interaction. This dynamic complexity raises methodological problems about what to score for experimental studies. We present a scoring schema that is sensitive to the correlated nature of the actions performed. Two experiments illustrate how these measurements can be used to detect the effect of brain damage on play fighting even when there is no effect on overall playfulness. That is, the schema presented here is designed to detect and evaluate changes in the content of play following an experimental treatment.

Abstract

Play fighting in the rat involves attack and defense of the nape of the neck, which if contacted, is gently nuzzled with the snout. Because the movements of one animal are countered by the actions of its partner, play fighting is a complex, dynamic interaction. This dynamic complexity raises methodological problems about what to score for experimental studies. We present a scoring schema that is sensitive to the correlated nature of the actions performed. The frequency of play fighting can be measured by counting the number of playful nape attacks occurring per unit time. However, playful defense, as it can only occur in response to attack, is necessarily a contingent measure that is best measured as a percentage (#attacks defended/total # attacks X 100%). How a particular attack is defended against can involve one of several tactics, and these are contingent on defense having taken place; consequently, the type of defense is also best expressed contingently as a percentage. Two experiments illustrate how these measurements can be used to detect the effect of brain damage on play fighting even when there is no effect on overall playfulness. That is, the schema presented here is designed to detect and evaluate changes in the content of play following an experimental treatment.

Introduction

Rats have been the most intensively used animals in the laboratory with which to study play^{10, 21, 41}, and several attempts have been made to develop scoring schemes to measure the effects of experimental treatments on play fighting^{8, 9, 37, 38, 39}. However, while these schemes have had some success in monitoring the frequency of play, they are less suitable as ways to monitor changes in the content of play due to their lack of sensitivity to the dynamics of the interaction¹³. The main problem is that, during fighting, the use of tactics by one partner is often contingent on the performance of particular tact....

Protocol

1. Equipment and Room Set Up

1. The play box apparatus is a clear, Plexiglas box measuring 50 cm X 50 cm X 50 cm with 1-2 cm of standard corncob bedding.
2. All filming is conducted in the dark via a handheld camcorder under the night-shot option.
3. The camcorder is placed at a 45° angle facing downwards towards the play box on a tripod. All four corners must be visible in the shot to obtain a full view of the apparatus.

2. Methodology

1. Animals are weaned between postnatal days 21-23. Depending on the experimental design, animals can be housed together in groups of 2-4 in the required male and femal....

Results

Two studies illustrate how the multi-faceted scoring scheme that we have developed can be used to diagnose the effects of experimental manipulations on the play fighting of rats. The first shows that the method can be used to pinpoint the specific component of play changed by an experimental manipulation and the second shows how the method can be used to measure changes in the relationships following an experimental manipulation.

(1) The effects of neonatal decortication

Discussion

Play fighting is a complex, dynamic interaction in which the participants continually influence each other's behavior. As a consequence, a scoring scheme that is sensitive to those dynamics and the contingent nature of the actions performed is needed. The scheme outlined in this paper has proven successful in comparing across sexes, individual differences, through development, strain differences and for experimental treatments^{4, 14, 16, 20, 24, 29, 30, 31, 32, 32, 36}. Moreover, the scheme presented can.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Sony DCR-DVD103 Camcorder			Optical Zoom- 20x, Night shot *See Below
Play Apparatus			50 X 50 X 50 cm Plexiglas
* Any camcorder will work for recording, although an optical zoom of 20x or above is desired for optimal zoom.