Do Dogs Distinguish Rational from Irrational Acts?
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Animal Behaviour 81 (2011) 195e203 Contents lists available at ScienceDirect Animal Behaviour journal homepage: www.elsevier.com/locate/anbehav Do dogs distinguish rational from irrational acts? Juliane Kaminski a,*, Marie Nitzschner a, Victoria Wobber b,1, Claudio Tennie a, Juliane Bräuer a, Josep Call a, Michael Tomasello a a Department of Comparative and Developmental Psychology, Max Planck Institute for Evolutionary Anthropology b Department of Human Evolutionary Biology, Harvard University article info Range et al. (2007, Current Biology, 17,868e872) found that dogs, Canis familiaris, copy others’ means to Article history: achieve a goal more often when those means are the rational solution to a problem than when they are Received 27 May 2010 irrational. In our first experiment, we added a further control condition and failed to replicate this result, Initial acceptance 6 July 2010 suggesting that dogs in the previous study may have been distracted in the irrational condition rather Final acceptance 28 September 2010 than selectively attending to the irrational nature of the action. In a second experiment, the demon- Available online 2 November 2010 strator used an unusual means (an extended leg) to communicate the location of food, either rationally MS. number: 10-00368R (her hands were occupied) or irrationally (she could have used her hand). Dogs succeeded in finding the food irrespective of whether the leg action was rational or irrational. Our results suggest that dogs do not Keywords: distinguish rational from irrational acts, instead simply being proficient at monitoring human Canis familiaris behavioural patterns. communication Ó 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. dog imitation rationality From an early age, human children interpret others’ actions as evidence that children from an early age understand the efficiency goal-directed in social-learning situations, for example, copying or ‘rationality’ of others’ actions (Gergely et al. 2002; Buttelmann their intended rather than their actually performed acts (Meltzoff et al. 2007, 2008). 1995), and their purposeful rather than accidentally performed In recent years several pieces of evidence have suggested that acts (Carpenter et al. 2005). In addition, Gergely et al. (2002) nonhuman species may also be able to interpret the rational showed that 1-year-old children copy others’ actions based on dimension of others’ actions. For example, Buttelmann et al. (2007) their ‘rationality’, that is, based on the assumption that actors take had human-raised and -trained chimpanzees, Pan troglodytes, into account constraints on behavioural efficiency. Specifically, observe a human perform actions using unusual means such as infants watched an adult turn on a lamp using her forehead. Half of switching on a light with his foot rather than his hand. As in the the infants observed this action while the adult’s hands were studies with human infants, sometimes the means were rational occupied by holding a blanket, making this a reasonable, efficient because the experimenter’s hands were occupied, but sometimes ‘back-up action plan’, whereas the other half of the infants saw the they were irrational, because his hands were free. Just like human same action but here the adult’s hands were free (while a blanket infants, these chimpanzees copied the unusual means more when was merely placed around the adult’s shoulder), which made her the experimenter’s hands were free than when they were occupied, choice of means inexplicably inefficient. Infants who observed the suggesting that they attend to the rationality of others’ intentional adult perform the unusual means when she had a good alternative actions (see also Buttelmann et al. 2008). later reproduced this unusual action more than those who There is also evidence that a species more distantly related to observed the adult being forced to use this action because of the humans, the domestic dog, Canis familiaris, copies others’ actions lack of a good alternative. This study has been interpreted as more often when those actions are the efficient (‘rational’) solution to a problem than when they are not. Range et al. (2007) had a demonstrator dog move a rod attached to a box down to release * Correspondence: J. Kaminski, Max Planck Institute for Evolutionary Anthropology, a piece of food. This effect on the box could be achieved in two Deutscher Platz 6, D-04103 Leipzig, Germany. separate ways: the rod could be pushed down with the paw or it E-mail address: [email protected] (J. Kaminski). 1 V. Wobber is at the Department of Human Evolutionary Biology, Harvard could be pulled down with the mouth. As established in a baseline University, 11 Divinity Avenue, Cambridge MA 02138, U.S.A. condition, using the mouth was the preferred method employed by 0003-3472/$38.00 Ó 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.anbehav.2010.10.001 196 J. Kaminski et al. / Animal Behaviour 81 (2011) 195e203 naïve dogs (i.e. witnessing no demonstration). The demonstrator free. If dogs attend to the rationality of others’ actions, they should dog, however, always used the less preferred action (the paw) to discriminate between the rational and irrational cue, performing operate the rod. Sometimes this was the efficient/rational thing to better when the cue is rational because the irrational cue may do because the dog carried a ball in her mouth, making it impos- represent a random movement, rather than a deliberate signal. sible for her to use her mouth. Alternatively, using the paw was an inefficient/irrational thing to do, because the demonstrator did not EXPERIMENT 1 carry a ball in her mouth, thus eschewing the preferred action for no reason. This experiment aimed to replicate Range et al.’s (2007) finding In line with human infants and human-raised chimpanzees, that dogs reproduce others’ actions selectively based on an inter- observer dogs preferred to use the mouth when they had observed pretation of the efficiency of those actions. In this experiment, we the demonstrator using the paw with her mouth occupied, but they used the same basic method used by Range et al. (2007) but we preferred to use the paw when they had observed the demon- added two additional control conditions. strator using the paw with her mouth free (Range et al. 2007). This indicates that dogs not only attend to others’ goal-directed actions Methods during demonstrations, but also that they copy others’ choice of means to perform a certain action. The finding of both action Subjects copying and selectivity is difficult to reconcile with previous studies We used 74 dogs, which lived as pets with their owners. Most of social learning in dogs, which claim that dogs’ social-learning dogs had a special training background with regard to certain skills may not be very sophisticated. For example, Tennie et al. activities such as dog dancing or agility (see Table 1 for a detailed (2009a) had a demonstrator dog perform one of two trained description). Dogs were selected based on breed and training actions (e.g. rolling over) upon hearing a verbal command (fol- background to match the dog sample used by Range et al. (2007) to lowed by a reward each time). After observing this demonstration the highest degree possible. Dogs were tested with their owners five times, observer dogs still failed to copy any of the demon- present. The demonstrator dog was a 3-year-old female Border strated actions in this setting, even though observers saw the collie. Again this dog was chosen to match the breed and sex of the demonstrator receive food after each successful performance. This demonstrator dog in the original Range et al. (2007) study. paradigm was substantially different from the Range et al. (2007) study, for example the actions were intransitive rather than tran- Materials and experimental set-up sitive (object-directed), but still it seems that dogs may not be The apparatus (Fig. 1) was a replica of the one used in Range particularly robust imitators in all situations. et al. (2007). To release the food, the operator had to pull down In most studies testing rational imitation in children or a wooden bar in the direction of gravity. This then opened the primates, researchers control for the differential influences of the baited box and let the food drop to the ground. The apparatus was potential distractor/activator objects. In the studies of Gergely et al. attached to a large stable object, such that dogs could be tested (2002) and Buttelmann et al. (2007) those objects (e.g. the blanket outdoors or indoors, depending on the weather conditions. The in the Gergely et al. 2002 study) had been present in both the apparatus was attached such that the wooden bar (the manipu- restrained and unrestrained conditions. For example, in Gergely landum) was hanging at the level of the dog’s shoulder. et al.’s study the blanket around the demonstrator’s shoulders Each dog had to pass a pretraining task to enter the experi- could have distracted the children and/or could have activated mental phase. certain behaviours (perhaps ‘placing the head to sleep’). Thus, if the blanket were present only in their hands-occupied condition, then Procedure this could have had the potential to explain their findings. In other Pretraining. To ensure that dogs were able to perform both words, it is important to control for the effects of such objects. The potential actions on the wooden bar (‘mouth’ and ‘paw’), we first Range et al. (2007) study was missing such a key control condition. trained them in the task (again, to follow the method used by Range In Range et al.’s two main conditions observer dogs watched the et al.