Which experimental protocols can be used to study formally the presence or absence of emotions in non verbal beings, such as other animals than humans? Is there a survey about such results and/or experiments?


In a recent (June 2023) video, the eminent Stanford neuro endocrinology professor Robert Sapolsky states (at 1:36) that emotions are "very much a mammalian specialty, lizards are not well known for their emotional life". I was surprised, as I thought that it wad well known that non mammals (such as birds) do display a wide range of emotions.

On the other hand, a (dubious?) recent article titled "Deciphering Avian Emotions: A Novel AI and Machine Learning Approach to Understanding Chicken Vocalizations" (June 2023, researchsquare.com) claims to describe an experiment in using AI to translate the sounds emitted by 80 chicken into emotional states as varied as "happiness", "hunger", "tiredness", "pain", and "fear".


An online search yields (non scientific) articles stating that "There is no scientific agreement about whether or not birds have feelings" and confusing arguments opposing emotion and instinct (The Spruce.com, 2019-04-11); or asking whether "Birds Have Feelings and Emotions?" (learnbirdwatching.com, undated) with a mitigated answer (without references) that "it’s widely acknowledged that birds have basic emotions like fear and pleasure, what about more complex emotions like love or grief?":

This is a question that has been debated for centuries, as there is no scientific evidence to definitively answer it. However, it is widely accepted among pet owners and birdwatchers that they do indeed possess feelings and emotions. Animals, including birds, are capable of exhibiting behaviors such as love, pleasure, fear, joy, excitement, anger, depression and sadness – all of which can be interpreted by humans as emotional states.

Among the scientific articles, the best I could find was a 2019 article by Papini et al. titled "Avian Emotions: Comparative Perspectives on Fear and Frustration". It states that "Comparative psychologists have struggled with the problem of emotion because, as many other important concepts, they cannot be directly observed or measured." (and refers to Darwin's study of facial expressions), and concludes that "the evidence for fear in birds seems stronger than the evidence for frustration", all based on a survey of previous results.


I find it hard to believe that those are the only results known about emotions in other animals than mammals (and in particular in birds). As I am studying some Quaker parrots using home-made video games, in which the subjects do exhibit (what I interpret as) both positive emotions such as satisfaction and negative emotions (which I do my best to reduce) as frustration, studying more formally their emotional states seems like a good research opportunity, but I would like to avoid re-inventing the wheel...


1 Answer 1


Q: Do non-human animals experience emotions?

I believe the closest we have to a scientific consensus on the matter is "The Cambridge Declaration on Consciousness":

Mammalian and avian emotional networks and cognitive microcircuitries appear to be far more homologous than previously thought. ... Non-human animals, including all mammals and birds, and many other creatures, including octopuses, also possess these neurological substrates.

Q: Is it possible to reliably detect emotion X in individuals of non-verbal species Y (or birds in general)?

Kremer et al (2020) provide a great review of emotion research in general. The problem is that whether detecting emotion X in individuals species Y where Y is human is reliably possible non-verbally, depends on the theory of emotion that you subscribe to. The field of emotion research remains divided about the existence of reliable non-verbal assessment of emotion even in humans! Thus, it is more conservative to concentrate on what is known as "core affect" - a 2-dimensional subjective state that universally underlies all emotion (though even this has been disputed!) - as exampled below.

Q: What experimental protocols can be used to detect core affect or general mood states in birds?

For a broad overview of general research protocols in animal emotion, try Wikipedia. The Kremer et al (2020) paper mentioned above also contains an extensive review.

One well-researched approach is the "judgement bias test":

For example, on many trials, if the animal presses lever A after a 20 Hz tone it gets a highly desired food, but a press on lever B after a 10 Hz tone yields bland food. The animal is then offered both levers after an intermediate test stimulus, e.g. a 15 Hz tone. The hypothesis is that the animal's "mood" will bias the choice of levers after the test stimulus; if positive, it will tend to choose lever A, if negative it will tend to choose lever B.

This test is often used to assess how environmental factors affect the mood of subjects, and has been evaluated in several species of birds (eg, Lagisz et al, 2020; Paul et al, 2022). The discrimination power of this test for small differences in affect is limited, and different variants of the test also vary in power, so the most appropriate alternative for a given context may be worth further investigation.

Another popular approach for measuring general animal emotional welfare is a "qualitative behavioural assessment":

Qualitative Behaviour Assessment (QBA) is a method that relies on the ability of human observers to integrate perceived details of behaviour, posture, and context into descriptions of an animal’s style of behaving, or ‘body language’, using descriptors such as ‘relaxed’, ‘tense’, ‘frustrated’ or ‘content’. Such terms have an expressive, emotional connotation, and provide information that is directly relevant to animal welfare and could be a useful addition to information obtained from quantitative indicators. Previous research with pigs, cattle, sheep and poultry consistently showed QBA to have high inter- and intra-observer reliability and to be coherent with quantitative behavioural and physiological measures, both when animals were assessed individually and at group level.

This method has also been used with several species of birds (eg, Vasdal et al, 2022; Rose & Riley, 2019; Souza et al, 2021; Fleming et al, 2016).

Other options include:

  • Consumer demand: Mood affects subject choices between interchangeable resources.
  • Preference tests: Subjects select their preferred environment directly.
  • Psychoactive drugs: Subjects self-medicate more when stressed.
  • Physiological tests: An assortment of physiological stress indicators are available.
  • Attention bias: Mood affects attention to threatening stimuli.
  • Play behaviour: Most species of birds play more when less stressed.
  • There are many other potential indicative behaviours applicable to birds, such as exploration, problem-solving, and social grooming.
  • Neurological correlates of emotion states are under development, as are AI-based methods.

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