Visual and social determinants of shock-elicited aggressive responding in rats

Abstract

Light and dark reared, social and isolate housed, male Long-Evans hooded rats were tested in bright and dim light for aggressive response to footshock. Test lighting and socialization main effects were significant, with greater fighting in dim light than in bright light and greater fighting by isolates than by socially housed animals. Test lighting interacted with prior visual experience and socialization interacted with past and present illumination variables. The results suggest an inhibitory effect of test illumination dependent upon prior social and visual experience.The importance of posture and related threat (Knutson & Hynan, 1972: Reynierse, 1971Vernon, 1969) would appear to implicate visual cues as significant variables in shock-elicited aggression of rats. Flory, Ulrich, and Wolff (1965) investigated the influence of visual impairment by fitting leather hoods over the heads of their Ss. The rats were paired and given shocks over repeated sessions with and without the hoods in place. Hooding decreased fighting by approximately 50%. In a second experiment, a pair of blinded rats fought 27% less than prior to blinding; when also devibrissaed, the same pair fought at lower levels. The decrease in fighting originally noted with the use of hoods was attributed to both visual and tactual sensory restriction. More recently, Bugbee and Eichelman (1972) have compared pre-and postoperative fighting of blinded, devibrissaed , and bulbectomized rats, Contrary to the results of Flory et al (1965), no decrement in fighting was observed after blinding. Bulbectomized rats fought at near preoperative levels, while devibrissaed rats fought significantly less. Olfactory and visual factors were presumed to have a minor, if any, role in conspecific aggression.The present investigation sought to assess the role of past and present illumination on shock-elicited aggression. Visual history was manipulated by housing animals in light or darkness, and immediate visual cues were examined by testing in bright or very dim light. Prior social history (isolate or group housing) and aggressive experience (successive fights) were also examined for interactive effects with illumination variables. METHOD SubjectsSs were 48 male Long-Evans hooded rats. *Supported by NIH Research Grant MH 21577-01. ApparatusThe fighting chamber, a 20 x 20 x 20 em box of wood and Plexiglas, was enclosed within a fan ventilated light-and sound-attenuating chamber having a viewing portal and a 100-W incandescent lamp (mounted in a recessed ceiling fixture) that illuminated the fighting chamber. The grid floor of the fight chamber consisted of Y4-in. brass rods spaced 5{8 in. apart. Constant current shock was delivered from a Lafayette A-615A shock source through a Lafayette 5820 neon grid scrambler. ProcedureAll Ss were reared from birth with their littermates in constant darkness until weaning. At weaning, female pups were culled and the remaining male pups were randomly assigned to group pan cages containing four Ss each. At 45 days of age, half (N = 24) we...

The effects of social isolation on two shock-induced aggressive responses in rats

“…In that study, aggression was defined as boxing or biting, and it was noted that the isolation-reared groups displayed less shock-induced aggression but experienced more tissue damage. The analysis of the percentage of shocks evoking boxing or biting was not consistent with the conclusion that isolation results in more shock-induced aggression (Creer, 1975;Thor & Ghiselli, 1974). While the difference between the results of the present study and the data reported by Creer (1975) and Thor and Ghiselli(1974) could have been due to subtle differences in recording aggressive behavior, it seems more plausible that the differences in data are due to procedural differences among studies.…”

“…The analysis of the percentage of shocks evoking boxing or biting was not consistent with the conclusion that isolation results in more shock-induced aggression (Creer, 1975;Thor & Ghiselli, 1974). While the difference between the results of the present study and the data reported by Creer (1975) and Thor and Ghiselli(1974) could have been due to subtle differences in recording aggressive behavior, it seems more plausible that the differences in data are due to procedural differences among studies. Thor and Ghiselli (1974) used a round-robin procedure, and in the Creer (1975) study the test of housing conditions was confounded with familiarity between pair members.…”

“…While the difference between the results of the present study and the data reported by Creer (1975) and Thor and Ghiselli(1974) could have been due to subtle differences in recording aggressive behavior, it seems more plausible that the differences in data are due to procedural differences among studies. Thor and Ghiselli (1974) used a round-robin procedure, and in the Creer (1975) study the test of housing conditions was confounded with familiarity between pair members. In addition, the length of time in the two housing conditions was confounded with the age of the subjects in the Creer (1975) study.…”

“…In order to relate these data to similar studies of isolation and shock-induced aggression that did not distinguish between boxing and biting behavior (Creer, 1975;Hutchinson et al, 1965;Hutzell & Knutson, 1972;Thor & Ghiselli, 1974), the percentage of shocks presented to rat pairs that evoked biting orboxing were analyzed in a three-factor mixed analysis of variance. The only statistically significant effect was due to the second housing condition; the groups isolated during this period (01 and II) had lower scores on this combined aggression measure (F(l,24) = 17.56, P <.001].…”

“…Hutchinson, Ulrich, and Azrin (1965) and Hutzell and Knutson (1972) presented data indicating that isolation from weaning to adulthood results in less shock-induced aggression between rat pairs. Thor and Ghiselli (1974) tested community-reared and isolation-reared rats for shock-induced aggression in a round-robin test procedure, and indicated that isolation resulted in reduced shock-induced aggression during only the first of five test sessions and that rats raised in isolation displayed more aggression on succeeding sessions. Creer and Powell (1971) housed rats in isolation or in pairs from 20 days of age until shockinduced aggression testing commenced at 30, 60, or 90 days of age.…”