Comentário da Dra. Victoria Braithwaite, professora na universidade Pennsylvania State nos EUA, sendo uma renomada cientista internacional na área de comportamento e bem-estar de peixes:
“Sentience refers to an animal’s ability to experience its feelings; an awareness of what it is like to experience something positive or negative. As a human, I have no trouble recognizing that another person experiences emotions such as joy or sadness. We can talk to each other and describe our current feelings – this ability to verbally self-report helps us to understand each other’s emotions. But what about the animals we have as pets, the animals we farm for produce, or the animals we use in research – do they have feelings? Some animals certainly look like they do, but is that sufficient evidence to conclude that they do? It turns out that demonstrating animals feel their emotions is remarkably challenging.
Just a few decades ago, the idea that an animal might experience emotion was considered a topic that could not be scientifically studied. A movement, known as ‘Behaviourism’, believed that the scientific study of human and animal behaviour should avoid reference to internal states, and instead focus on observable behaviour, particularly the way certain stimuli lead to certain kinds of response. This meant that the study of animal emotion received very little attention, but more recently, this has been changing and there are now growing numbers of studies addressing felt emotion in humans and other animals.
Demonstrating when an animal experiences emotions is not straight forward. There have been many studies in the last 12 years exploring cognitive bias; these studies have tried to find ways that determine whether an animal is in a positive or negative mood state. But although these studies have been both clever, and informative, they do not tell us whether the animal is aware of its mood state. It is much harder, to demonstrate when, or whether, animals experience the emotions that result from being in a particular mood state.
Some of the most promising evidence comes from studies where animals are asked to report on their emotional state. For example, drugs can be given to animals to induce specific negative feelings in an attempt to try and train the animal to recognize a specific kind of emotion. One intriguing example of this approach by Carey and Fry (1995) attempted to train pigs using the drug pentylenetetrazole (PTZ) which induces a feeling of anxiety in humans. Pigs were trained that under control conditions they would receive a food reward by alternating pressing on one of two levers, but when treated with the PTZ no alternation was required. The pigs were then tested in situations expected to induce anxiety (such as transport by road), with the idea that the animals could report on their current state of anxiety by either alternating between the levers (no feelings of anxiety) or pressing on a single lever (feeling anxious).
Although this approach has a lot of appeal and seems intuitive, it has been hard to train animals in this kind of task, but current studies are hoping to use this kind of approach to gain a better understanding of when animal’s are aware of emotional states and thus when they are experiencing positive or negative states.”
Carey, M.P., & Fry, J.P. (1995). Evaluation of animal welfare by the self-expression of an anxiety state. Laboratory Animals, 29, 370-379.