punishment is a commonly used modifier of human and animal behaviour because it has been shown to be effective at reducing unwanted behaviour . for example
the effectiveness of punishment increases with its intensity ( e.g. , ) , and punishment is more effective if it is introduced abruptly at moderate intensity rather than faded in from low intensity .
however , the ethical implications of imposing punishment can lead to a desire to use less severe forms of punishment .
dog owners , in particular , are warned that physical punishment should never be used , and that , if used , punishment should be delivered remotely to avoid association of the owner with the aversive stimulus [ 4 , 5 ] .
antibark collars , as a form of remote punishment to reduce the vocalization of dogs , have several advantages .
they are capable of delivering different forms of aversive stimuli , for example , electric shocks or high - frequency sounds .
because the shock is triggered by vibrations from the dog 's larynx when the dog barks , punishment can be delivered consistently , and immediately , after the response , rather than haphazardly , or after a delay .
additionally , punishment delivered by an antibark collar is unconnected with the owner , reducing the likelihood that the owner will become a conditioned aversive stimulus that the dog learns to fear or become aggressive towards .
however , high intensity shocks may be overwhelming or cruel , causing skin lesions , chronic stress [ 9 , 10 ] , fear and pain responses [ 11 , 12 ] , and even death .
for humane reasons , dog owners are likely to prefer less intensely punishing solutions to their dogs ' barking behaviour . in one study ,
dog owners reported a preference for citronella- , or lemon - spray collars , which deliver a spray of citronella when a microphone detects barking , over shock collars , because they perceived them as more humane .
no significant difference was found in mean plasma - cortisol values ( a stress indicator ) between dogs that wore shock versus lemon - spray collars , and it is not clear whether lemon - spray collars result in fewer pain and stress reactions than shock collars .
however , previous research has shown that low - intensity punishment , such as that delivered by a citronella collar , may be less effective than intense punishment .
seven of nine dog owners in juarbe - diaz and houpt 's   study reported reductions in frequency , intensity , and duration of their dogs ' barking when they wore citronella collars for a 2-week period .
.   found lemon - spray collars to be just as effective as shock collars in eliminating barking .
the dogs ' barking was completely eliminated by the third day of wearing either a shock collar , or a lemon - spray collar , with both collar types being equally effective .
, however , did not evaluate whether the improvement was maintained over longer periods although they stated that there was no evidence of habituation when the dogs wore the collars intermittently over a 2-week period .
moffat et al .   also found citronella collars to be effective in reducing the barking of 77% of the dogs who received a 5  min application of the collar in a veterinary hospital .
the severity of barking was rated subjectively , however , and no followup was carried out to determine whether improvement was maintained .
wells   showed a greater reduction in the barking of dogs that wore citronella spray collars intermittently ( 30  min every other day ) than for dogs that wore the collars continuously ( 30  min every day ) over a 3-week period .
after a large initial decrease in the reported frequency of barking , barking frequency increased for both groups of dogs , but more quickly for dogs exposed more regularly to the collar .
after the 3-week treatment period , and 1 week without collar use , the frequency of barking had returned to pretreatment levels for dogs exposed to the collar every day in treatment .
barking frequency remained lower than pretreatment levels for the intermittent group but had not stabilised , and appeared to be still subject to an upward trend [ 17 , figure  1 ] .
wells   did not attempt to measure behavioural reactions of the dogs to the collars ( such as stress or fear ) , and the efficacy of the treatment was based on subjective owner ratings of the frequency of barking .
we had two main aims in addition to measuring the efficacy of mild punishment delivered via citronella collars in reducing vocalization of domestic dogs .
firstly , we set out to measure the longer - term effectiveness of citronella collars , by measuring vocalization across multiple treatment sessions , and 3 months after the end of the treatment phase .
we sought to obtain a more objective measurement of barking than in previous research , by tape recording the dogs ' vocalizations .
secondly , we monitored the dogs for any signs of distress while using the collars .
dogs weighing less than 5  kg , or with previous experience of the citronella collar , were excluded .
all dog owners had received an official warning , a complaint from neighbours , or reported that their dog 's vocalizing reduced the quality of the dog 's relationship with the owner .
the data from three dogs ( s1 , s3 , and s9 ) are not shown here because their baseline levels of vocalization were extremely low prior to the application of the collar .
the aboistop collar contains a laryngophone which activates a spray jet via a selector . according to the manufacturer ,
the spray is activated by a 95  db - level bark . however , a - weighted testing in the psychophysics laboratory of the university of auckland indicated that the spray was triggered by an 80  db sound .
the collar is powered by a 6  v battery which lasts for an estimated 1000 sprays . a reservoir contained within the casing of the collar , and which sits on the dog 's throat , holds approximately 20 sprays of citronella . upon activation ,
a single spray of citronella is forced upward towards the dog 's mouth and nose upon each separate bark .
the canister makes a pressure release sound similar to a can of fly spray when activated .  
data were collected by videotape ( with a vhs gf-450 jvc video camera ) for dog s7 and audiotape ( with a bush c5100s ) for all other dogs .
thus , the conditions , and their order , were selected according to the needs of each dog and its owner .  
figure 1 shows the order of conditions and the number of sessions completed by each dog in each condition . in 
a  , or baseline , conditions , the aboistop collar was not applied . in 
b  conditions , vocalizations were recorded while some dogs wore an inactive aboistop collar .
this condition was included where the vocalization problem was nonurgent in order to test the effect of the introduction of a novel stimulus in the absence of citronella .
condition b1 was omitted with dogs whose owners sought a faster resolution of their dogs ' problem vocalization . 
owners received instruction on how to operate and test the collar and initiated the recording device for the duration of the session .
the second author was present for the first three c1 conditions for all dogs to ensure that owners were applying the collar correctly .
every instance in which the dog was exposed to the problem context was recorded . during the treatment phase
the second author contacted owners frequently to ensure they were applying the collar correctly , and recording every instance in which the dog was exposed to the problem context .
the treatment was applied as it would be by a novice pet owner who had purchased the collar .
that is , if the citronella canister emptied completely during a session , it was not refilled until the next session because , in standard use , the owner would be unlikely to be present to refill it .
similarly , any problems encountered during treatment , such as the battery running low , or non - compliance with instructions , were assumed to be representative of typical owner use of the device .
condition c1 was terminated for dogs s6 , s7 , and s10 after 15 , 4 , and 6 sessions once it was determined that the collar did not effectively reduce their vocalization .
active collars were used for a maximum of two weeks for the remaining dogs . when vocalization appeared to be eliminated under active collar condition ( c1 ) , the collar was inactivated ( b2 ) in an attempt to generalise behaviour control so that the collar could eventually be removed without recurrence of the vocalization .
a session began with a cue identified by the dog owner as a trigger for the dog 's vocalization .
the mean duration ( and standard deviation ) in minutes of sessions was 11 ( 6 ) , 60 ( 0 ) , 60 ( 0 ) , 19 ( 15 ) , 72 ( 26 ) , 9 ( 11 ) , 12 ( 8) for dogs s2 ,
three dogs ( s4 , s5 , and s7 ) vocalised when home alone , so session length was determined by the usual length of the owners ' absence .
session length was set at 60  min for dogs s4 and s5 and was usually 60 , 90 , or 120  min for s7 .
session length necessarily varied for the other four dogs because they vocalised during car journeys .
follow - up sessions were conducted three months after the final session for dogs s2 , s4 , s5 , and s8 .
dogs s2 and s4 conducted the followup under baseline conditions because their vocalizations were successfully reduced and the collar was no longer required .
dogs s6 , s7 , and s10 did not participate in follow - up sessions because the collar was not effective at reducing vocalization , and treatment was discontinued .
thereafter , reactions were monitored by the dog owner , and regular home visits were made by the second author to assess the dogs ' well being .
the criteria for behavioural reactions were largely based on those observed in the studies of piette   and brunelat .
the second author used a partial - interval recording method to quantify the prerecorded data .
a stopwatch was used to time each interval and record the duration of each session . for each 10-s interval ,
any occurrence of a vocal response was noted with a tick and the absence of a vocal response with a cross .
a vocal response was defined as howling , whining , or barking . for each session ,
the percentage of each session that contained vocalisations was analysed both graphically and statistically ( see below ) .  
reliability checks were conducted on a random 10% of sessions across all phases . a psychologist trained to use the recording method recorded the presence or absence of vocalizations , separately , but at the same time , as the primary observer .

 figure 1 shows the percentage of 10-s intervals containing vocalization for each dog for each session .
conditions are displayed in the order completed ( reading left to right ) . using a graphical analysis , for two ( s5 and s8 ) of the three dogs whose baseline condition ( a1 ) was followed by an inactive collar condition ( b1 ) , vocalization was reduced by the application of the inactive collar . for s8 , vocalization was quickly restored to baseline levels in b1 .
the citronella collar appeared to be effective at eliminating vocalization for dogs s4 and s5 and reducing vocalization for s2 .
the effect generalised to collar - absent situations for all three dogs although vocalization was never completely eliminated for s2 .
the collar was ineffective for the remaining four dogs , with vocalizations increasing to baseline levels over time .
dog s6 's vocalizations were lower for homeward journeys ( marked with a + in figure 1 ) than for outgoing journeys , showing that the collar was not effective in all situations . using a statistical analysis
, a paired t - test showed that mean vocalisations were significantly lower during the first session with the active collar applied ( c1 ; mean = 7.85 ) compared to the mean for the last baseline session ( a1 ; mean = 39.69 ; t(9 ) = 2.26 , p = .01 ) .
however , a paired t - test comparing the mean for the last baseline session with the mean of the last c1 session for each dog ( mean = 35.50 ) was no longer significant ( t(9 ) = 2.26 , p = .52 ) .
these results suggest that the initial reduction in vocalisation produced by the active collar was not maintained with continued use .  
dogs for whom the citronella collar appeared effective at eliminating or reducing vocalization ( s2 , s4 , and s5 ) were characterised by a shorter vocalization history ( mean = 5.33 months , sd = 5.77 , min = 2 , max = 12 months ) than those dogs for whom the collars were not effective ( s6 , s7 , s8 , and s10 ; mean = 24 months , sd = 12.96 , min = 12 , and max = 42 months ) . during exposure to
the citronella collar , dogs commonly froze , shook their heads , sneezed , and jumped backwards .
dog s5 showed serious distress reactions , hiding under a veranda and trembling continuously during the latter sessions of condition c1 .
the results indicate that , when the aboistop collar was applied by dog owners , it was effective for three of the seven dogs , with vocalisation completely eliminated for two dogs , and reduced for one . for two of the three dogs ( s5 and s8 ) that experienced an inactive collar condition ( b1 ) ,
the initial reduction for s8 may have been due to this dog 's previous exposure to a shock collar . simply introducing a novel stimulus , however ,
indeed , given that four dogs did not experience the inactive collar condition ( b1 ) , the initial reduction in vocalization seen for dogs s6 , s7 , and s10 when the active collar was applied ( c1 ) may also be due to the introduction of a novel stimulus , suggesting that the active collar itself may never have been effective for them .
although we can not conclude that the collars are ineffective on dogs with a long history of excessive vocalization , the implication is interesting . in practice ,
owners whose dogs have a short history of vocalization problems are probably less likely to use antibark collars , as dog owners will tend to seek nonaversive methods before aversive ones to remedy the behaviour problems of their dogs .
head - shaking , vigorous movement , and panting sometimes resulted in inappropriate activation of the collar .
the collar not only released citronella in the absence of barking but also failed to release citronella following some vocalizations .
further research on anti - bark collars , which could be conducted under artificial conditions , should investigate the reliability of the relationship between vocalization and activation of the collar .
one owner experienced a malfunction when the collar suddenly exploded and left a dent in the ceiling of his living room . the manufacturer , dynavet france , reported that 70 of 100,000 collars sold by them had also exploded ( dynavet , pers .
luckily , the collar was sitting on a table and not being worn by the dog or held by the dog owner , at the time .
distress reactions associated with the activation of the collar suggest that a spray of citronella was only mildly aversive to most dogs and were linked to the spray 's novelty .
however , the citronella collar was clearly more aversive for some dogs than for others .
indifference to the citronella collar appeared to develop in condition c1 for dogs s6 and s10 and condition c2 for dog s8 .
the owners of these dogs observed that the collar was drained of citronella due to continuous vocalization .
thus , in conditions of normal use , the citronella collar may quickly lose its effectiveness if vocalization occurs at a high rate .
given that stronger punishment is more effective , it may be that citronella collars do not sufficiently punish problem vocalizations .
dog owners may perceive citronella collars as more humane than shock collars   but should be aware that a low - intensity punisher , such as the citronella anti - bark collar , is less likely to be effective at reducing the problem behaviour than stronger punishment . using any level of punishment via an anti - bark collar to reduce the vocalizations of dogs
is ethically concerning , particularly when the problem behaviour occurs in the owner 's absence , as there is no one present to ensure that the collar is not causing undue suffering . in summary , while the small sample size precludes unequivocal evidence of the efficacy of citronella collars , it appeared effective for three and ineffective for four of the seven dogs .
thus , citronella collars may be effective for reducing or eliminating the vocalisations of some dogs but not others . in our study
, it appeared that the collars were more effective with dogs that had a shorter vocalisation history .
for other dogs , an initial reduction in vocalisation when the active collar was applied was not maintained with continued use .
 the aim of our study was to investigate whether citronella - spray collars offer a humane alternative to electric - shock collars to reduce the barking of domestic dogs . 
 the aboistop collar was applied to seven dogs with problematic barking behaviour by the dogs ' owners in a series of case studies concurrently run . 
 vocalisation of the dogs was recorded in the problem context under baseline conditions , inactive collar conditions , and active collar conditions . 
 the aboistop collar was effective at reducing problem vocalization for only three of seven dogs and appeared to be most effective for dogs whose problem barking had developed more recently . 
 the collar may be more humane than other punishment methods , but it did produce stress reactions which varied in severity across the dogs . clinical relevance . in our study , 
 the collar was applied by the dogs ' owners in order to test whether the collar would be effective when used by members of the public . while the results here are preliminary , they suggest that the collar may be effective for some dogs , but not for others , when applied by dog owners for the treatment of problem vocalisation . further research is required to determine whether the collar could be effective when administered by a trained professional . 
1. Introduction
2. Method
3. Results
4. Discussion