Assessing positive emotional states in dogs using heart rate and heart rate variability

Abstract

A test session consisted of four presentation phases (1 st exposure to stimulus, post exposure, 2 nd exposure, and access to reward). Heart rate (HR) and heart rate variability (HRV) responses were recorded during testing in the experimental room and also when lying resting in a quiet familiar room. A new method of 'stitching' short periods of HRV data together was used in the analysis. When testing different stimuli, no significant differences were observed in HR and LF:HF ratio (relative power in low frequency (LF) and the high-frequency (HF) range), implying that the sympathetic tone was activated similarly for all the stimuli and may suggest that dogs were in a state of positive arousal. A decrease of HF was associated with the meatball stimulus compared to the food pellet and the reward phase (interacting with the person or eating the food) was associated with a decrease in HF and RMSSD (root mean square of successive differences of inter-beat intervals) compared to the preceding phase (looking at the person or food). This suggests that parasympathetic deactivation is associated with a more positive emotional state in the dog.A similar reduction in HF and RMSSD was found in the test situation compared to the resting situation. This is congruent with the expected autonomic effects related to postural shift i.e. sympathetic activation and parasympathetic withdrawal, during standing versus lying, but it cannot explain the parasympathetic deactivation in response to the more positive stimuli since the dogs were always standing in the test situation. We discuss the systematic pattern of responses, which support that increased HR and LF:HF ratio are associated with emotional arousal, but add the new proposal that a combined decrease in A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT3 RMSSD and HF may reflect a more positively valenced emotional state even when an individual is already in a positive psychological state.

How good is this food? A study on dogs' emotional responses to a potentially pleasant event using infrared thermography

“…In line with previous literature on humans and many other animal species [24,47,63,78,79], the results of this study indicated that mean HR (corrected for dynamic components of behavior) was linked to emotional arousal. Nevertheless, HR provides limited…”

“…While the literature on positive emotions in farm animals has grown [5,27,[33][34][35][36][37][38][39][40][41], the same topic has received little attention in companion animals [42][43][44][45][46][47]. Dogs' positive affective states have been investigated in female laboratory beagles tested in four different experimental protocols:…”

“…tail wagging, proximity and contact seeking, gazing, stress signals, and vocalizations [42][43][44][45][46][47]), physiological (HR and HRV [44,47]), endocrine (oxytocin and cortisol [45]), and neural (hemodynamic [46]) indicators.…”

“…Given that very palatable food is considered a positive reward [15,21,36,38,40,59] and based on the recent evidence by Zupan and colleagues [47], we hypothesized that a very palatable food treat received from the owner should attract dogs' attention toward her/him, significantly increasing gazing behavior [60] and should also be a source of arousal, determining an increase in HR [47,61,62]. In addition, since HRV reflects the continuous interplay between the two branches of the ANS and it has been suggested that HRV changes are associated to the positive valence of emotional state [34,35,47], we expected that heart rate variability parameters should vary.…”

“…In addition, since HRV reflects the continuous interplay between the two branches of the ANS and it has been suggested that HRV changes are associated to the positive valence of emotional state [34,35,47], we expected that heart rate variability parameters should vary. HRV could increase [63] or decrease [47] and therefore at the present stage of knowledge on dog emotional reaction is difficult to make a more precise hypotheses. Finally, if receiving treats induced in dogs a positive emotional state we should observe an increase in tail wagging [43].…”