location in an object-choice task. In this study, we used acomplex experimental situation in which, on the onehand, we used 4 possible hiding locations instead of 2and, on the other hand, there were 2 experimenters gestur-ing simultaneously at the 2 bowls, while the owner alsopointed at the one experimenter who pointed to the baitedbowl in the testing trials. In the control trials everythingwas the same as in the testing trials except that the exper-imenters did not point but kept their arms beside theirbody and looked at the floor while the owner pointed tothe experimenter who hid the reward into one of the bowlsas she did in the testing trials. In the second study (n 5 12),we examined whether dogs can understand indirect infor-mation about the place of a hidden object (i.e., if they can-not observe the hiding directly but can get informationabout the location of the hidden object through differentsignals, like touching, pointing, or a using marker) andthen pass this information to the owner. Complexity wasprovided in this study with the increased number of signalsused and the temporal shift in the signaling scheme (theshift occurred before the dogs had the opportunity toshow soliciting behavior to the owner.)In the first study, we used the Wilcoxon matched pairs test tocompare the dogs’ performance between the control and thetest trials. We found that at the group level they performedsignificantly better in the test trials than in the control trials((T1) 5 127.0; P , 0.05). We compared the dogs’ perfor-mance to the expected chance level (25%) in both trialswith one-sample Wilcoxon signed-rank tests. We foundthat whereas the dogs performed significantly above chancelevel in the test trials their performance was at chance level inthe control trials (test trials: (T1) 5 190.0; P , 0.001; con-trol trials: (T1) 5 86.0; P 5 0.37). In the second study, wecompared the duration of time spent looking at the baitedand the empty bowls in each situation and found that dogsspent significantly more time looking at the baited bowl inall situations. The comparison of the behavior displayed bythe dogs in the different trials showed that the dogs’ behaviorwas similar in the different test situations.Overall, our results show that dogs are able to use indirectsignals in relatively complex situations but their perfor-mance in the present studies also could be explained byrelatively simpler mechanisms, such as facilitation andlocal enhancement.

Key words: dogs; gestural communication; indirect signals;pointing

Communication and associated cognition 59

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DO DOGS TALK TO EACH OTHER? FIELD INVESTIGATIONSON DOG–DOG ACOUSTIC COMMUNICATIONEva Szabo*, Marta Borgi, Csaba Molnar, Peter Pongracz,Adam MiklosiEthology, Eotvos Lorand University, Hungary*Corresponding author: teltancoss@gmail.com

Dog–human communication has recently been extensivelyinvestigated. We found that dog barking is highly informativeto humans (Pongracz et al., 2005; Pongracz et al., 2006). Therole of dog barking still is not clear, however, in dog–dogcommunication. By measuring heart rate in the laboratory,it was shown that dogs can discriminate between barks,which were recorded in different contexts (Maros et al.,2008). The goal of this investigation was testing the effectof barking on dogs in their natural environment.We worked with owners who had at least 2 adult dogs. Atfirst we recorded the barks of all dogs in 2 contexts: ‘‘leftalone’’ and ‘‘stranger arrives’’; these recordings served asplayback material later. Each dog was tested 4 times, withfamiliar and unfamiliar barks, from both contexts. Therewas a minimum 2-day interval between the 2 tests. Duringthe test, only 1 dog was out in the yard; the owner and theother dogs were in the house. The playback device washidden outside the yard, within 1 meter of the fence. Dogs’behaviors were recorded with 2 cameras in the yard, andthe bark responses were recorded by a DAT device. A testsession consisted of three 1-minute periods (pre-bark, bark,and post-bark).Playing back barks had a significant effect on the dogs’behavior (repeated-measures analysis of variance [ANOVA]):the number of barks (F(2,14) 5 56.60; P , 0.001), frequencyof gate orientation (F(2,14) 5 15.27; P 5 0.001), moving to-ward the gate (F(2,14) 5 31.45; P , 0.001), and moving atthe gate (F(2,14) 5 20.48; P , 0.001) were higher in thebark period than in the pre- or post-bark periods. We didnot find a clear effect of context and familiarity of the barkson the dogs’ behaviors, with the exception of the frequency ofgaze alternation, where we found several interactions. Dogsshowed more gaze alternations between the source of soundand the house when they heard familiar barks (repeated-measures ANOVA; F(1,14) 5 7.06; P , 0.01). We also founda strong significant effect of dominance rank of the subjectson their responses to bark playbacks.Our results show that dogs react to other dogs’ barking, andtheir responses depend somewhat on the familiarity and thecontext of the barks. These results support the theory thatbarking can have a role in dog–dog communication.

Key words: acoustic communication; dog; barking;contextual meaning

References:

Pongracz, P., Molnar, Cs., Miklosi, A., Csanyi, V., 2005. Human listeners

are able to classify dog (Canis familiaris) barks recorded in different

situations. J. Comp. Psychol 119, 136–144.

Pongracz, P., Molnar, Cs., Miklosi, A., 2006. Acoustic parameters of dog

barks carry emotional information for humans. Appl. Anim. Behav.

Sci 100, 228–240.

Maros, K., Pongracz, P., Bardos, Gy., Molnar, Cs., Farago, T., Miklosi, A.,

2008. Dogs can discriminate barks from different situations. Appl.

Anim. Behav. Sci 114, 159–167.