Previous studies in our laboratory have demonstrated that a naive rat (an observer), after interacting briefly with a previously fed conspecific(a demonstrator), will exhibit an enhanced preference for the diet its demonstrator had been fed. The present studies were undertaken to determine whether demonstrator-induced alterations in observer diet preference were the result of simple exposure of observers to diet-identifying cues emitted by demonstrators during the period of demonstrator-observer interaction. Our results indicated that observer experience of diet-related cues in the stimulus context provided by the presence of a demonstrator was sufficient to enhance observer preference for a diet, whereas simple exposure to that diet was not. We concluded that demonstrator influence on observer diet preferences was not the consequence of simple exposure of observers to demonstrator-emitted cues reflecting demonstrators' diet.
Following interaction with a "demonstrator" rat, an "observer" rat prefers that diet eaten by its demonstrator prior to their interaction ). The present series of studies demonstrates that such demonstrator influence on observer diet preference can be found in: (1) firstgeneration laboratory bred wild rats as well as domesticated rats, (2) food-deprived as well as nondeprived observers, (3) unfamiliar as well as familiar demonstrator-observer pairs, (4) both 21-day-old and adult observers, and (5) rats selecting fluids as well as solids for ingestion. These data indicate that the social transmission of information concerning distant diets is a general and robust phenomenon, observable under a wide variety of experimental conditions.Results of recent studies have demonstrated that during a brief period of interaction a naive rat (an observer) can extract from a recently fed conspecific (a demonstrator) information sufficient to permit observer identification of the particular food its demonstrator has eaten. This transfer of information from demonstrator to observer is evidenced by enhanced preference by observers for that diet eaten by their respective demonstrators Galef, Wigmore, & Kennett, 1983;Posadas-Andrews & Roper, 1983;Strupp, 1982). Such demonstrator effects on observer diet preference are not the result of simple exposure of observers to the odor of the diets eaten by their respective demonstrators. Demonstrator influence on observer diet preference requires that an observer experience a diet in the context of stimuli (as yet undefined) provided by the presence of a conspecific. Thus, it seems appropriate to think about demonstrator influence on observer diet preference as reflecting a rudimentary form of communication or information transmission from one individual to another. The occurrence of such communication might be inhibited by any of a number of factors.Although transmission between rats of information concerning distant diets has been demonstrated in a number oflaboratories, each using somewhat different procedures, there has been no systematic exploration of the range of experimental conditions under which social transmission of diet preference occurs. The published literature thus leaves unanswered questions as to the robustness and generality of the phenomenon. In the experiments reported below, we examine the effects of subject genotype, sub- ject age, subject motivational state, demonstrator-observer familiarity, and the nature of the ingesta selected by observers on the transmission of preference for distant diets.
GENERAL METHOD
SubjectsSubjects in all experiments described below were same-sex demonstrator-observer pairs of rats. Except as otherwise noted, the observers were experimentally naive 42-day-old Long-Evans rats obtained from Blue Spruce Farms (Altamont, NY) and the demonstrators were 90-day-old rats that had served as observers some weeks earlier.
ApparatusThe subjects were housed and tested as demonstrator-observer pairs in 42.5 x 24 x 27.5 em wire-mesh hanging cages (Wahma...
Observer rats interacted with conspecific demonstrators immediately after demonstrators ate a novel diet and were made ill by LiCI injection. Following their interaction with demonstrators, observers were tested for aversion to their ill demonstrator's diet. Previous research has shown that (a) an observer can extract information from a demonstrator sufficient to permit identification of the demonstrator's diet (Galef & Wigmore, 1983) and (b) a rat ill from LiCI toxicosis is an adequate unconditioned stimulus in a taste aversion learning paradigm (Lavin, Freise, & Coombes, 1980). Further, two of the present experiments demonstrated that cues emitted by a rat, reflecting the particular diet it has eaten, are an adequate conditional stimulus in a toxicosis-induced aversion learning situation. Observer avoidance of a diet previously ingested by an ill demonstrator was, however, not demonstrated. The implications of the failure to find socially mediated aversion learning are discussed.
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