Post-learning experience matters: Chewing after learning improves memory consolidation in dogs

Post-learning interventions, such as exercise or play, have been shown to improve memory consolidation in dogs, but add time and cost to the training procedure. Chewing has been shown to positively affect some cognitive measures in humans and rodents. If chewing improved memory consolidation post-learning, providing an edible, long-lasting chew could be a time-efficient way to speed up the training process. This study therefore investigated the effect of chewing on memory consolidation in dogs. Kennelled dogs were trained in a two-choice object-discrimination-task. They then either received a whole long-lasting chew (treatment group, n = 16, oral activity mean ± SE: 14.9 ± 1.3 min), or the same chew crushed to facilitate quick consumption while controlling for the effect of nutrient intake (control group, n = 15, oral activity mean ± SE: 1.8 ± 0.2 min). Dogs of both groups were then re-tested the following day in the same task. Treated dogs that received the whole chew reached a pre-defined learning criterion in significantly fewer sessions on Day 2 than control dogs. In addition, duration of oral activity post-learning across both groups was negatively associated with number of sessions needed to reach learning criterion the second day, indicating that a longer duration of oral activity improves memory consolidation. To explore possible effects of chewing on secondary readouts, which could affect memory consolidation, we measured activity, heart rate and heart rate variability post-chewing in subsets of dogs. We detected a group x time interval interaction in the ratio of low frequency to high frequency bands (LF/HF ratio), with dogs in the control group having a higher LF/HF ratio approximately 90 minutes post-chewing than dogs in the treatment group, while there was no difference between groups approximately 30 minutes post-chewing. These findings may point towards a higher sympathetic activity and a potentially less relaxed state in the control group compared with the treatment group, although results of the secondary readouts need to be interpreted with caution due to the small number of dogs sampled. The results of this study show that chewing favours memory consolidation, thus suggesting this to be an efficient post-learning intervention in dog-training contexts. • Chewing for 15 min post-training sped up re-learning of a discrimination task. • Prolonged chewing post-learning may facilitate memory consolidation in dogs. • Preliminary heart rate variability data indicate chewing may reduce sympathetic tone.