No abstract

No abstract

No abstract

Many "higher" animals are commonly assumed to distinguish between individual humans. This belief is based largely on anecdotal reports; in reality, there is little empirical evidence to support human recognition in nonhuman species. Wereport that laboratory rats consistently chose a familiar human over an unfamiliar human following fourteen and five IO-min exposures and even following a single IO-min exposure. Furthermore, this preference was retained in the absence of additional contact for at least 5 months. These results confirm that laboratory rats can tell individual humans apart, a prerequisite for associating them with hedonic events. Such human-based conditioning, described by Pavlov and by Gantt, Newton, Royer,and Stephens (1966),may have important implications for animal research in a variety of settings.Can the ubiquitous laboratory rat recognize individual humans? There is evidence that, like many animals, rats can discriminate individuals within their own species (Halpin, 1980; Hopp, Owren, & Marion, 1985;Randall, 1989). Indeed, Thor and Holloway (1982) describe rats as "normally engaging in spontaneous learning of individual identity" (p. 1000). But can such individuals be of another species, and, more specifically, can they be human?The recognition by animals of individual humans is not without precedent. For example, there is evidence that dogs (Settle, Sommerville, McCormick, & Broom, 1994), sheep (Fell & Shutt, 1989), pigs (Tanida, Miura, Tanaka, & Yoshimoto, 1995), and prairie dogs (Slobodchikoff, Kiriazis, Fischer, & Creef, 1991) can tell humans apart. However, there is as yet no comparable evidence that rats can distinguish individual people.Whether rats can discriminate between humans may have implications beyond the study of animal cognition. If research animals, such as rats, can differentiate one human from another, and this human is repeatedly paired with significant hedonic events in the animal's life, Pavlovian conditioning is likely to occur. Most research entails the delivery of hedonic stimuli, either through daily care or experimental manipulation. Gantt, Newton, Royer, and Stephens (1966) recognized this human-based conditioning process and described it in terms of "person as CS." Davis and Balfour (1992) surveyed evidence that such an associative process may have motivational effects that raise methodological concerns for animal-based research.This research was supported in part by Grant A0673 to the first author from the Natural Sciences and Engineering Research Council of Canada. All animals were cared for in accordance with the University of Guelph Animal Care Policy and Canadian Council on Animal Care guidelines. A portion of these data was reported at 1994 meetings ofthe Animal Behavior Society and the Psychonomic Society. The authors wish to thank Lill Svendsen and Susan Boehnke for their technical assistance. Correspondence should be addressed to H. Davis, Department of Psychology, University of Guelph, ON, Canada NIG 2WI (e-mail: hdavis@uoguelph.ca).Although it is not o...

Vocalizations during competition among nursing piglets were studied to investigate their possible effects, functions and implications for welfare. In Expt 1, two experimental piglets in each of 14 litters were temporarily deprived of milk by covering their preferred teats on the sow’s udder. These piglets spent more time away from their teats than two control piglets, and vocalized frequently in the 2 min before milk ejection. Frequency of vocalization showed no consistent change over time within nursings; nor did it change in successive nursings despite the fact that hunger presumably increased. In Expt 2, tape recordings of intense vocalizations (screams) produced by piglets competing at the udder were played to 22 litters while they were nursing; each litter was played its own recording, a recording from another litter and silence as a control. Of 51 nursings analysed, 14 were terminated without milk ejection, all during playbacks. When the sow did nurse successfully during a playback, nursing was shorter (138 s) than during the silent controls (179 s). Both these responses by the sow might be expected to advance the next nursing. Piglets rarely showed any apparent response to screaming either from their littermates or from the loudspeaker. These results suggest that the calls function mainly as a signal to the sow that some piglets are being excluded from the current nursing episode.