#### What is sentience? sentience is from Latin _sententia_ that means “feeling”. So any system capable of feeling, any system for which it is to be like _something_ is sentient. Basic sentient organisms need not necessarily involve higher-order consciousness related functions such as reflection, self-awareness, dreaming, episodic memory or cognition. All sentient organisms have feelings/experiences while only some have higher order consciousness. See [[What is consciousness?]] for more on this. As per [Feinberg and Mallatt](https://mitpress.mit.edu/books/consciousness-demystified), there are two components of this primary sentience: 1. Experience of a (representation) mental image of the sensed world (required for simulating actions and their consequences before organism takes it) 2. Affective feelings, good or bad as the most basic form (responsible for communicating consequences of simulation so that actions can be guided towards positive ones, and away from negative ones) The usefulness of sentience may lie in anticipating rewards and punishment, and doing actions that may lead to rewards and less punishment. #### Who is capable of suffering? Until we know [[Causal mechanisms for consciousness and suffering]], we can only go by what scientists say about who is capable of suffering. Those organisms that have operant learning about rewards and punishments. (from [Debunking a myth: plant consciousness](https://link.springer.com/article/10.1007/s00709-020-01579-w)). (Operant learning is association of voluntary behavior and a consequence, while classical learning is association of involuntary behavior and a stimulus). ![[1200-607827-46303084-64768013.jpg]] The claim is that only the organisms capable of operant learning are capable of suffering. (As classical conditioning can happen mechanically while operant learning requires representing the world inside as a mental image to get what you want and take a voluntary action even when no sensory stimulus is present) Pain is a simulation of death that evolution stumbled upon to prevent organisms from finding out too late what can kill them. So, if an organism is merely reactive and is not capable of being proactive / anticipating reward or punishment, it's not sentient. (Although the reverse may not be true). "Truly proactive behavior that indicates consciousness would be to find the goal _in the absence of a sensory trail_, based on a mental map of the surrounding environment". **Who suffers:** - Vertebrates (Mammals, birds, fish, fish), arthopods (insects, crabs) and cephalopods (e.g., octopuses, squids). - See [Cambridge declaration of consciousness](https://fcmconference.org/img/CambridgeDeclarationOnConsciousness.pdf) - As per [Plants Neither Possess nor Require Consciousness](https://www.cell.com/trends/plant-science/fulltext/S1360-1385(19)30126-8) - "Based on their evolutionary analysis of the structure, organization, and functional specialization of the brain required for the emergence of consciousness, Feinberg and Mallatt concluded that the only animals that satisfied their criteria for consciousness were the vertebrates (including fish), arthropods (e.g., insects, crabs), and cephalopods (e.g., octopuses, squids)." - "Consciousness must have appeared independently by convergent evolution in each of the three animal lines, because reconstructing their history indicates their last common ancestor lacked a brain" [Debunking a myth: plant consciousness](https://link.springer.com/article/10.1007/s00709-020-01579-w). **Who doesn't suffer**: - Plants - Argument - Plants cannot move to protect itself from danger, so there's no need for suffering/pain to evolve - Plants do not have brains - See [Plants Neither Possess nor Require Consciousness](https://www.cell.com/trends/plant-science/fulltext/S1360-1385(19)30126-8) - "No single plant organ or tissue functions as ‘the plant brain’, integrating all of the signals affecting plant growth and development. If the root tip is a brain-like command center, then so, too, is the shoot tip, the coleoptile tip, the leaf, the stem, and the fruit." - "While it is true that some plant cells are electrically excitable and that electrical signaling is involved in some plant stress responses, not all electrical excitability represents communication with other cells... excitability for osmotic regulation is evolutionarily much older than excitability for information transmission" - "While it is true that substances such as diethyl ether interfere with touch-sensitive action potentials and rapid leaf movements, this inhibition represents a general effect of anesthetics on membrane properties." - "In angiosperms, coevolution with insects and other animals harnessed the motility and intentionality needed for cross-pollination, obviating the need for the evolution of these traits. There is no evidence that plants require, and thus have evolved, energy-expensive mental faculties, such as consciousness, feelings, and intentionality, to survive or to reproduce" - and [Debunking a myth: plant consciousness](https://link.springer.com/article/10.1007/s00709-020-01579-w). - Three main reasons for rejecting plant consciousness: - 1) "plants have not been shown to perform the proactive, anticipatory behaviors associated with consciousness, but only to sense and follow stimulus trails reactively;" - (2) "electrophysiological signaling in plants serves immediate physiological functions rather than integrative-information processing as in nervous systems of animals, giving no indication of plant consciousness;" - (3) "the controversial claim of classical Pavlovian learning in plants, even if correct, is irrelevant because this type of learning does not require consciousness."" - "Phloem-conducted action potentials in plants are commonly responses to noninvasive and nondamaging environmental stimuli, such as touch, cooling, and light (Fromm and Lautner 2007; Fromm et al. 2013; van Bel et al. 2014; Gallé et al. 2015). By contrast, the defense responses to destructive wounding and burning injuries are signaled by variation potentials (VPs, sometimes called “slow wave potentials”), which are also conducted by the phloem. Accompanying these VPs are waves of Ca2+ and reactive oxygen species in the cytoplasm (van Bel et al. 2014; Evans and Morris 2017; Nguyen et al. 2018; Toyota et al. 2018; Lew et al. 2020; Klejchova et al. 2021), with the defense responses including accumulation of jasmonate, salicylic acid, ethylene, and other adaptations to stress. VPs merit special attention because they are especially relevant to the question of whether plants have the conscious experience of pain. That is, injury-induced VPs are the closest functional analogues in plants to the nociceptive neural signals that lead to conscious pain in animals. Nociception in animals is the nonconscious sensing of injurious stimuli and is not itself pain, but it is processed into pain by higher-level neuronal signaling (Draguhn et al. 2020). Therefore, if the electrical properties of plant VPs resemble nociceptive signals, then **it is conceivable that plants could also feel pain. Does such a resemblance exist? No, VPs are different from nociceptive action potentials, and from anything expected to code for consciousness**. Plant VPs travel slowly, at only about 0.001 m s−1 (Zimmermann et al. 2009; Mousavi et al. 2013), far below the 0.5–2 m s−1 of the slow nociceptive action potentials that propagate along human axons after wounding (Purves et al. 2018). Unlike action potentials, new VPs can be generated only every 10 min to several hours (Klejchova et al. 2021) and they decay over time and distance (decreasing in amplitude). Each VP is unitary and long-lasting (for over 5 min: Nguyen et al. 2018). VPs cannot signal all the way from one end of a plant to another, either by amplitude or velocity. Another characteristic that precludes neuron-like encoding by VPs is that they are highly variable in amplitude and temporal behavior, unlike the frequency encoding that characterizes electrical spike trains in neurons and is necessary for consciousness in animals (Dennett 2015; Klejchova et al. 2021)." - In plants, "forward signals are documented but feedback signals have not been found" - Counterpoint: - [Plants Feel Pain and Might Even See](https://nautil.us/issue/104/harmony/plants-feel-pain-and-might-even-see) - Anesthesia works on plants (venus fly trap stops working when anesthesia is applied to it) - "Plants do pass information from cell to cell just like we do, via ion channels. That’s probably where lidocaine does its work in plants, blocking these channels and cutting off communication. That’s why the hair cells in the Venus flytrap can’t tell the motor cells to contract, there’s no signal being passed between them." (via [here](https://news.ycombinator.com/item?id=25591443)) - "There’s a vine that grows in South America that adapts to the form of the tree or bush it is climbing on" - [Should fish feel pain? A plant perspective](https://www.wellbeingintlstudiesrepository.org/cgi/viewcontent.cgi?article=1052&context=animsent) - "Plants synthesize almost all known neurotransmitters." - "Plant roots are very active organs, searching for mineral nutrients and water in the darkness of an underground environment." (Darwin hypothesized that roots could be brains of plants) - " Already in 1878, Claude Bernard stated that “what is alive must sense and can be anesthetized, the rest is dead.” He thereby proposed sensitivity to anesthetics as a prime criterion of life" - [Are plants sentient?](http://www.esalq.usp.br/lepse/imgs/paginas_thumb/Are-plants-sentient---Anthony-Trewavas.pdf) - " The phloem is the pathway for electrical communication, with the plant nervous system based on action potentials transmitted along vascular conduits stretching throughout the whole plant body." - Bose was the Father of plant electrophysiology. He was the first one to demonstrate that electrical signals in plants are carried by phloem. In 1926, Bose published The Nervous Mechanism of Plants. - "In young trees, damage or cold shock to one leaf is experienced by other leaves remote from the signal" - "The initiating signals currently known to induce action potentials include herbivory and physical damage, leaf and fruit removal, rapid stressful temperature variations, light–dark changes, mechanical stress from bending, amongst others. The balance between photosynthesis and respiration is often diminished. Repair and resistance mechanisms, both short and long term, are induced." - The point regarding movement is very anthromorphic. Just because a life form doesn't move, doesn't mean it is not sentient. It can have different ways of defending itself (like selectively releasing a noxious or poisonous chemical where it's being attacked) - In plants, The acquisition of short‐term animal memory parallels synaptic strengthening that lasts from minutes to hours and is mediated through glutamate sensitive Ca2+ channels" - Complex behaviors of plants - Leaves moving to be positioned to be right angles to light or average light direction - Release of ethlyene when leaves are eaten/damaged by caterpillars - Homeostatic regulation of internal temperature to ~20degrees centrigrade even though outside temperature could be a higher or lower. They do this by changing leaves density, position, reflection properties and so on - #openquestions - If a plant is subject to shade situations and to a mild deprivation of water, which response would be prioritized? Would the stem increase or decrease its growth? Would the stem grow faster to avoid shade, or resources instead be given to enhance root exploration for water? - Worms: - "**Caenorhabditis elegans (C. elegans), which is the representative nonconscious animal** (Barron and Klein 2016: Klein and Barron 2016). When foraging in soil for its bacterial food, this worm continually uses many senses (taste, smell, touch, moisture) to track and find the richest bacterial patches (Ardiel and Rankin 2010; also see Gang and Hallem 2016), and it usually succeeds, especially when, upon losing the trail, it conducts a thorough and patterned search." (via [Debunking a myth: plant consciousness](https://link.springer.com/article/10.1007/s00709-020-01579-w).) - Fungi - Bacteria and single celled organisms **Uncertain, but unlikely to suffer**: - AI systems / code - https://reducing-suffering.org/which-computations-do-i-care-about/ ### Principles to judge who is capable of suffering As we're fairly confident that humans suffer from pain and emotionally, similarities on following dimensions between humans and other systems can be evaluated in order to judge whether that system feels pain or not: - **Functional or anatomical similarities** - Pain pathways / receptors same or similar to humans can be observed across different species. This suggests pain exists in those organisms - After noxious stimulus, chemicals such as endorphins or cortisol get released which can be measured - Application of opioid agonists (such as morphine) can mediate the behavioral responses (such as elevated heart rate or writhing) indicating that subjective pain has been reduced - However, great care must be taken in making such comparisons because during evolution, similar functions could get located at different places or implemented in different ways. For example, cortex in mammals is pallium/tectum in birds or fishesh - **Behavioral similarities** (immediate withdrawal) - Pain causes aversion from pain-causing stimulus. Hence, we can see what different systems are averse to and possibly conclude a negative valence state associated with perception/imagination of those - **Learning / adaptive similarities** (long term avoidance) - If a particular stimulus is learned to be avoided (e.g. fish can learn to avoid hooks and/or humans can learn to avoid blades), we must conclude pain should exist in both - **Motivational state similarities** - Pain changes the overall state / emotional of an organism such that the organism displays less exploration of environment and interpretation of neutral stimulus as negative (rather than positive) - Pain makes seeking of analgesic agents and/or even paying a cost for accessing analgesic agents Read more: https://www.sciencedirect.com/science/article/abs/pii/S0003347214003431 #### Analyzing counter-argument: why fish do not feel pain To understand this issue of what systems are capable of suffering, let's try to understand arguments behind a well-cited but controversial paper: [Fish do not feel pain and its implications for understanding phenomenal consciousness](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4356734/) In this paper, the authors imply that fish do not feel pain by relying on following arguments: - **Functional or anatomical considerations** - Fish lack brain structure (like neocortex in humans) that allows for integration and amplification of signals which are necessary for phenomenal consciousness - **Aversion behavior** - Mere presence of reflexive behavior does not imply phenomenal consciousness. For example, rats with injured spinal cord display protective reflexes when noxious stimulus is applied - **Adaptive learning to avoid noxious stimulus** - Fish without brains can still learn adaptive behavior that associated with avoiding noxious stimulus (albeit partially or slowly) I don't find the argument convincing because of the following reasons: - **Functional or anatomical considerations** - The same function can be implemented in different ways. For example, eyes have a variety of different implementations across species and yet the same function - vision - is common. I find it it troubling that the author has taken two features that are well known for human brains (reciprocal connections and signal amplifications) and suggested that since we don't know whether these exist for fish, fish may not be conscious. The issue with this line of argument is that: a) we do not know enough about fish brains so amplification or reciprocal connections may very well be there; b) these may exist with less intensity or even no intensity and yet evolution may have found some other way to instantiate the same function of pain / consciousness. - **Aversion behavior** - Reflex actions are unconscious to our self. But as elaborated in [[What is a Self?]], there may exist different selves at multiple levels and the reflex action may be conscious/painful to that particular self. - Moreover, just because we aren't conscious of reflex actions doesn't mean fish isn't conscious of them too. Perhaps, lacking higher level reflective consciousness or self-awareness, fish is very much conscious of reflex actions. - **Adaptive learning to avoid noxious stimulus** - This was the weakest argument in the paper as the author himself admits that fish with ablated forebrain was mostly incapable of learning adaptive behavior. Quotning the author: "However, it has been consistently reported that although avoidance learning by fish is perturbed by full or partial forebrain ablations, these animals continue to exhibit escape responses (and many continue to learn to avoid) as a result of electric shock" #inbox