Interpreting Joy In Nonhuman Animals
Biologists have long recognized that many species of animals experience emotions, which have adapted over time to support survival, learning, and social behaviors. However, research into positive emotions in nonhuman animals is relatively scarce, in part because they are more difficult to detect and measure compared to negative emotions. The authors of this article explain that joy, a positive emotion characterized as “intense, brief, and event-driven,” may be an excellent subject of study in animals, due to its association with visible markers like vocalizations and movement. More research about joy could potentially provide us with a deeper understanding of cognitive processes and evolution, but also enable us to better monitor and facilitate animal wellbeing.
While research on joy in humans has relied heavily on introspection and self-reporting, this is typically not possible with other species, at least not in ways we can immediately understand. The authors suggest that the best way to measure the presence of joy in nonhumans is to create joy-inducing situations and collect evidence from the resulting behavioral responses. In reviewing the current literature, the authors describe four areas that may prove most fruitful in studying joy in nonhumans: 1) optimism, 2) subjective wellbeing, 3) behavioral indicators, and 4) physiological indicators.
- To measure optimism as an indicator of positive emotion in animals, researchers use the cognitive bias test. This involves training animals to recognize one stimulus as positive and another as negative, and then to present them with a third ambiguous stimulus that is exactly between the two others. The animals are then identified as more optimistic or more pessimistic based on how quickly they approach the ambiguous third thing. The cognitive bias test has also been seen to link positive emotion to positive bias in humans, providing a valid path forward for scientists to continue using it as a tool to better understand joy in animals.
- Joy can also be viewed as a sub-dimension of subjective wellbeing, which can be measured on a short-term level in animals by connecting it to physiological responses. For example, lower cortisol levels indicate lower stress and therefore higher wellbeing. However, this type of research can run the risk of anthropomorphizing certain behavior, such as play. While many researchers agree that play in animals indicates positive affect, other studies have suggested that play can also be associated with stress, which would indicate the opposite.
- Certain behaviors are likely correlated with strong positive emotions, particularly in mammals. These include vocalizations and facial expressions, many of which are similar to those exhibited in humans. Many species produce sounds during play that can be described as laughter, which serves an evolutionary purpose by being “emotionally contagious,” and is linked to dopamine activation in the brain. Meanwhile, facial expressions showing disgust or liking are studied in a variety of species, including birds, by looking at their physical responses to bitter or sweet flavors. While expressions can be often misinterpreted — requiring a control group to measure against each time — the authors of the review point to machine learning as a way of more accurately coding facial behaviors in different species.
- Physiological indicators in the brain can be a very useful way to study positive emotions like joy, because many species of animals share similar basic brain components and brain processes that date back to our common ancestors. Emotions occur in the subcortical regions of the brain, which means that a developed prefrontal cortex and high-level thinking, as seen in humans, are not required. Emotions in humans and nonhumans (vertebrates, at least) alike are found to be mediated by dopamine and opiate receptors, and affected by external rewards and hormones. For example, oxytocin may be associated with a positive state, while cortisol increases in stressful circumstances. Far more research into the effects of neurotransmitters on neurobiological processes is needed.
Current research suggests strong commonalities between human and nonhuman emotions. The authors of this article stress the need for a comparative approach to better understand the expression of joy across species. In doing so, we’ll gain deeper insight into our mutual origins and experiences, which could in turn promote better treatment of animals in so many ways.
https://doi.org/10.1111/brv.12965