Preference for familiar humans by rats

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...

Playful handling by caretakers reduces fear of humans in the laboratory rat

“…Rats took less time to approach, spent more time interacting with, and produced more 50-kHz USV in the presence of, the familiar than the unfamiliar hand, consistent with a previous report that rats prefer familiar compared to unfamiliar humans (Davis et al, 1997). They were less active in the presence of the familiar hand, probably because they spent more time near the hand rather than moving around the box.…”

Comparison of 2 gentling programs for laboratory rats: Effects on the behavior toward humans

“…Although both gentling programs were able to achieve a similar "taming" effect, the duration of the effect was dependent on how the gentling program was executed. A long-term effect similar to the one observed with the "intensive" gentling program was also reported by Davis et al (1997): In this study, adult rats, that were accustomed to daily handling, were petted for 10 minutes a day by the same person for 14 days and fed treats. The rats recognized the person who had gentled them and preferred her over an unfamiliar person.…”

“…In addition, it was shown that rats are able to distinguish between different people, and that they prefer familiar humans (McCall et al, 1969;Davis et al, 1997).…”

“…Gentling is a widely acknowledged method to influence the later behavior of laboratory rats, and numerous studies have been carried out to investigate its effects (e.g., Weininger, 1954;Weininger et al,1954;Weininger, 1956;Candland et al, 1960;Eells, 1961;Candland et al, 1962;Hirsjärvi and Junnila, 1988;Davis et al, 1997;Maurer et al, 2008;Cloutier et al, 2012). It should be noted that the term "gentling" is interpreted differently by different authors and that the gentling programs were applied in different life stages of the rats.…”

The influence of body region, handler familiarity and order of region handled on the domestic cat's response to being stroked

“…Such a finding is somewhat surprising considering research from other species has shown that a familiar handler is usually preferred to one that is unfamiliar. For example, cattle are quicker to approach and show decreased flight response to familiar individuals (Breuer et al, 2003) and rats are more likely to choose to have physical contact with a familiar handler (Davis et al, 1997). Furthermore, when considering pet species, dogs have been shown to demonstrate more social approaches when handled by a familiar person, although the familiar person in this case, was not their owner (Kuhne et al, 2012).…”