Evaluating the Strange Situation Procedure (SSP) to Assess the Bond between Dogs and Humans

<div><p>The Strange Situation Procedure (SSP) is increasingly being used to study attachment between dogs and humans. It has been developed from the Ainsworth Strange Situation Procedure, which is used extensively to investigate attachment between children and their parents. In this experiment, 12 female beagle dogs were tested in two treatments to identify possible order effects in the test, a potential weakness in the SSP. In one treatment (FS), dogs participated together with a ‘familiar person’ and a ‘stranger’. In a control treatment (SS), the same dogs participated together with two unfamiliar people, ‘stranger A’ and ‘stranger B’. Comparisons were made between episodes within as well as between treatments. As predicted in FS, dogs explored more in the presence of the familiar person than the stranger. Importantly, they also explored more in the presence of stranger A (who appeared in the same order as the familiar person and followed the same procedure) than stranger B in SS. Furthermore, comparisons between treatments, where a familiar person was present in FS and stranger A was present in SS, showed no differences in exploration. In combination, these results indicate that the effect of a familiar person on dogs' exploratory behaviour, a key feature when assessing secure attachment styles, could not be tested reliably due to the order in which the familiar person and the stranger appear. It is proposed that in the future only counterbalanced versions of the SSP are used. Alternatively, since dogs reliably initiated more contact with the familiar person compared to the strangers, it is suggested that future studies on attachment in dogs towards humans should focus either on the behaviour of the dog in those episodes of the SSP when the person returns, or on reunion behaviour in other studies, specially designed to address dog-human interactions at this time.</p> </div

The level of physical contact with humans initiated by dog in both treatments.

<p>Time spent in physical contact with person (median proportion of sample points/episode presented together with 95% confidence intervals) during the whole test procedure (episodes (Ep) 1–6) in treatment FS and in treatment SS. F = familiar person, S = stranger, S_A = stranger A and S_B = stranger B.</p

A schematic representation of predictions.

<p>Closed boxes refer to episodes where either F (familiar person) or S (stranger) was present in the room in the FS (familiar stranger) treatment or S_A (stranger A) or S_B (stranger B) was present in the room in the SS (stranger stranger) treatment. The arrows indicate the comparisons that were made. According to our hypothesis, if the ASSP is a reliable method to use when assessing the bond between dogs and humans, dogs should <i>explore</i> (EXP) and <i>play</i> (PLAY) more in the presence of the familiar person and they should show more <i>proximity seeking behaviours</i> (PROX) towards the familiar person.</p

Exploration levels in both treatments during the test.

<p>Level of exploration (median proportion of sample points/episode presented together with 95% confidence intervals) across the whole test procedure (episode (Ep) 1–6) in treatment FS and treatment SS. F = familiar person, S = stranger, S_A = stranger A and S_B = stranger B.</p

Overview of the test area.

<p>The black lines represent the tape on the floor that divided the larger room (room 1) into five zones (1: Near entrance door, 2: Neutral zone, 3 and 4: familiar person's/S_A's zone and stranger's/S_B's zone each containing a chair, 5: Neutral zone containing a rope tug-toy). The entrance door is at the left hand side of the figure and there is a door between room 1 and room 2 shown to the right in the picture. Room 2 was empty and was available to the dogs from episode 4.</p

Using judgement bias to measure positive emotional states in dogs

Interest in the induction and measurement of positive affective states in non-human animals is increasing. Here, we used a test of cognitive (judgement) bias, based on the finding that individuals experiencing different affective states judge ambiguous stimuli differently, to measure whether a positive low arousal affective state (e.g. ‘satisfaction’/’contentment’) could be induced in domestic dogs as a result of their experiencing a food-based rewarding event. In this rewarding event, subjects (1yr old female Beagles) had to search for small amounts of food randomly placed within a maze arena. Using a balanced within-subjects design, the dogs (N=12) received a cognitive bias test either without experiencing the rewarding event (the ‘Neutral’ treatment), or directly after experiencing the rewarding event (the ‘Post-consumption’ treatment). In the test, dogs were trained that one visual cue (e.g. dark grey card) predicted a positive event (food in a bowl) while a different cue (e.g. light grey card) predicted a relatively ‘negative’ event (empty bowl). We hypothesised that dogs tested after experiencing the rewarding event, and in a presumed post-consummatory positive affective state, would be more likely to judge visually ambiguous stimuli (intermediate grey cards) positively, compared to dogs in the ‘Neutral’ treatment. In contrast, we found that they took significantly longer to approach an intermediate ambiguous stimulus, suggesting that they were less likely to anticipate food (a negative judgement) compared to dogs in the ‘Neutral’ treatment group. Various explanations for the observed results are discussed, in particular how reward acquisition and consumption may influence positive affective state induction in animals

Episode description.

<p>Episode overview of the protocol used in treatments FS and SS where the dog, a familiar person (F) and a stranger (S) participated in treatment FS and the dog, stranger A (S_A) and stranger B (S_B) participated in treatment SS.</p

Proximity seeking behaviours.

<p>The median proportion of sample points/episode (lower; upper 95% confidence interval) of dogs being oriented towards the door and located near door during episodes 4 (dog alone) and 5 (familiar person present (in treatment FS) or stranger A present (in treatment SS)).</p