Recent Studies Suggest That Octopuses Actually Are Capable Of Feeling Physical And Emotional Pain

Scientific American

When it comes to animals, man is aware that many of them are actually able to feel both physical and emotional pain. House pets, for instance, show loneliness when they are separated from loved ones. Penguins mate for life, while some swear by the fact that dolphins can actually shed tears.

Other creatures, however, are often overlooked. Man isn’t always aware how these animals feel and whether or not, they do get affected by changes in their environment. Surprisingly, recent studies reveal that octopuses are more than capable of intense emotions.

A study recently published in iScience suggests that octopuses are likely to feel and respond to pain like mammals. This is the first of its kind when it comes to presenting solid evidence for an invertebreate to act in this capacity. In truth, pain more than just a simple reflex response to harmful stimuli or painful injury. It’s actually a more complex emotional state. Pain leads to distress and suffering, something that was more associated with mammals or vertebrates.


While it is known to most that vertebrates are capable of experiencing both the physical and emotional aspects of pain, it was a gray area for invertebrates. That’s because these species had a more basic nervous systems.

Octopuses were then involved in the study as they were the most neurologically complex invertebrates. In the past, there were little to no studies on how they had the capacity to experience such strong emotions. Neurobiologist Robyn Crook from San Francisco State University has been studying this for years. She set up her lab using  the same protocols for testing pain in laboratory rodents. She used the cephalopods – specifically, the octopus – to prove her hypothesis.

Crook made use of specified measurements of spontaneous pain-associated behaviors and neural activity. She had successfully identified three lines of evidence that all indicate how octopuses are capable of feeling negative emotions, especially when dealing with pain.  These creatures exhibited characteristics that mammals also show. This goes against the very belief that because their nervous system is organized in essentially different ways, they still do have the ability to experience pain.

The Guardian

While it’s difficult for scientists to interpret a subjective feeling or emotional state, Crook determined the behavior shown by octopuses prove that they are experiencing the physical and emotional components of pain that may be quite similar to mammals such as rodents. The emotion could also have lasting effects in their affective state. She noticed a change in their mood, feelings, and attitudes.

Crook argues, “Even in the absence of proof on conscious awareness or sentience in cephalopods, it remains clear that the responses demonstrated by octopuses in this study are so similar to those that would be expressed by mammals experiencing pain, that a reasonable, cautionary argument can be made that internal state of these disparate species is likely also similar.”

Crook has been involved in previous studies that show how octopuses can reflexively respond to noxious stimuli. In it, she noticed that they have learned to avoid them. The new research, on the other hand, went beyond the previous study. The octopuses went through a single training session in a three-chambered box. They each received an acetic acid injection into one arm. It showed how they avoided the chamber after the one shot. Those injected with non-harmful saline, however, did not avoid the chamber after.

After the octopuses were given the painful injection, they were then administered lidocaine (an analgesic). Crook observed how they preferred the chamber that offered them relief from pain. While those that received saline, on the other hand, didn’t show a preference.

Yahoo

The fact that the octopus chose a place that offered no harm is evidence of an affective pain experience.

Crook also discovered evidence that octopuses could discriminate between different qualities and intensities of pain in different the locations on their bodies.  Those given the acid groomed themselves more often, especially in the injection site. This happened during the full 20-minute training trial, as they attempted to remove a small area of their skin with their beak.

This study is different from the other studies involving peripheral pain responses. In this, the octopuses had their arms crushed or cut off. The simple acid injection produces a form of centralized response. In the study involving mammals, scientists found evidence on ongoing pain caused by sustained activity in the periphery. This showed evidence on long-term changes in the brain or spinal cord.

Cephalopods rely on their peripheral nervous system. It remains unclear how much of the new information makes its way to their central circuits. Crook made use of electrophysiological recordings to show that there is actually a prolonged peripheral response in the pathway to the brain. This may represent the intensity experienced. Moreover, these pain messages are immediately reversed with an analgesic. This is evidence of an intense pain experience.


The paper Crooks and her team put together concludes, “Together, these data provide strong support for the existence of a lasting, negative affective state in octopuses.” At this point, experts know that ongoing pain, as opposed to transient pain, is evidenced by mammals. Hence, it’s impressive how scientists were able to observe similar states in an invertebrate.

In fact, scientists also saw that cuttlefish are capable of passing the marshmallow test. This is a well-known cognitive test designed to measure a child’s ability for self-regulation. These new findings now raise ethical questions on the study and care for cephalopods. At the same time, it provides proof for novel evolutionary growth in the animal kingdom.

Crooks explains, “Our goal with this study was to move the question of invertebrate pain beyond reasonable doubt so that efforts to better regulate their humane use can proceed with a strong evidentiary foundation that until now, has been lacking.”

 

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