An acoustic signal may simultaneously provide information about the caller's species, sex, age, motivational state, dominance status, group membership, identity, and the social context. Several studies showed that nonhuman primate and other species were able to distinguish between individuals and contexts by only hearing vocalizations. We explored this phenomenon in family dogs. In the last decades only a few studies focused on the acoustic communication of dogs. Recently we showed that humans are able to categorize the barks into contexts and describe the emotional content. We found that humans with different levels of experience with dogs showed similar trends in experiments. On the other hand human listeners were not able to discriminate between individuals on the basis of their calls. In this present study we conducted play-back experiments to family dogs according to the habituation-discrimination paradigm. We investigated if dogs could discriminate between barks recorded from different individuals or in different contexts. Our results showed that dogs had this ability: subjects oriented more toward the speakers while a novel stimulus (bark recorded from another individual or in the other situation) was being played back to them. These and other findings suggest that bark may play a role in dog-dog and human-dog communication.

1. Human and dog
understanding of dog barks
Csaba Molnár, Péter Pongrácz, Antal Dóka, Ádám Miklósi
Department of Ethology
Eötvös Loránd University
molcsa@gmail.com
ISAE 2006 Celle

2. Bark as a communicative signal
 the main difference between the vocal repertoires of
dogs and wild canids is the frequency of occurrence
of bark (Feddersen-Petersen 2000)
 only a few studies focused on the acoustic
communication of dogs (e. g. Fox & Cohen 1976)
 assumed that as a result of domestication barking has
lost its role in communication (e. g. Tembrock 1976)
 bark is characterized by a few context- (motivational
state) specific acoustic parameters (Yin 2002)

3. Human understanding of bark
 humans can associate the barks with appropriate
emotional contents
 they have the ability to categorize barks into various
contexts
 people with different dog experience levels showed
similar trends (Pongrácz et al 2005)
 congenitally blind people performed similarly as
sighted people (Molnár et al 2006a in prep)

4. Emotional scores given by listeners
Stranger
4
3
Play Fight aggressiveness
2 fear
despair
1 playfulness
happiness
Ball Walk
Non-owners
Alone
Pongrácz et al. 2005

5.  the way humans describe the emotions in barks
parallels motivational-structural rules of animal
acoustics
(Morton 1977, Pongrácz et al 2006 in press)
 humans showed only modest accuracy in
discriminating between individuals of dogs by
only hearing their barks
(Molnár et al 2006b in press)
 a computerized algorithm for categorizing barks
seems to perform better than humans
(Molnár et al 2006c in prep)

6. A playback study with dogs
 the habituation-discrimination paradigm
 phase 1: the same stimulus three times (habituation)
 expected change: the behavioural response
declines
 phase 2: a ‘new’ stimulus (dishabituation)
 expected change: if the subject discriminates
between the new and previous stimuli then
response increases
 References: Janik, Rey 2002 (dolphin), Masataka 1985
(Japanese monkey), Hauser 1998 (Rhesus), Zuberbühler
2002 (Diana monkey)

7. The scheme of the paradigm
stimuli ‘A’ stimulus ‘B’
habituation dishabituation
magnitude
Response
time
1 2 3 4 trials

8. Questions
 Experiment 1: Are dogs able to discriminate between
barks recorded in two different contexts?
 Experiment 2: Are dogs able to discriminate between
the same barks if recorded from two different
individuals?

9. Method
 Subjects: family dogs, N=90
(test groups: N1,2=30; control group:
N=30)
 Stimuli:
 barks at a stranger intruding the
garden
 barks while leashed to a tree and
left alone (all barks recorded
from Mudis)
 duration of orientation toward the
speaker
 owner is present during the
experiment Stranger Alone

10. Experimental room layout
computer, recorder, monitor
microphone
owner and dog
camera
camera
camera and speaker

11. Experimental room layout

12. Results 1: Discrimination between contexts
12
*
10
orientation time (s) ± SE
8
6
NS
NS
4
**
2 NS
0 ***
1 2 3 4
stimuli
control (4th stimulus is the same), N=30 test (4th stimulus is different), N=30
RM ANOVAs (Molnár et al 2006d in prep)

13. Results 2: Discrimination between individuals
NS
10
9
orientation time (s) ± SE
8
7
6 NS
5 ***
NS
4
NS
3
2
1
0 ***
1 2 3 4
stimuli
control (4th stimulus is the same), N=30 test (4th stimulus is different), N=30
RM ANOVAs (Molnár et al 2006d in prep)

14. Conclusion
 Dogs are able to discriminate between barks
recorded in different contexts
 They are also able to distinguish between
barks of different individuals
 Their performances are not influenced by the
contexts of the habituation stimuli

15. Suggested research directions
 Are dogs able to discriminate between barks
of familiar and unfamiliar individuals?
 Can they distinguish the barks of different
dog breeds?
 Is it possible to teach dogs to recognize
barks?

16. Acknowledgements
 The authors are thankful to
 the members of Hungarian Mudi Club for
their assistance to the sound recordings
 Claudia DeRosa and other members of
research staff at Department of Ethology
for their help in recruiting subjects
 This study was funded by the grants of the
Hungarian Ministry of Education: FKFP No.
127/2001, and Hungarian NSF No. T047235