Also, I’m pretty sure that octopuses do play? A quick search appears to confirm this: “Octopuses like to play” (BBC).
I mention this in response to the part of the post that reads: “Other animals like fish, reptiles, and octopuses do not engage in sensation-seeking or play and so do not have those internal conscious experiences.”
(ETA: I see that in their closing section, OP acknowledges some uncertainty here, listing as a question for further investigation: “Is it really true that fish, shrimp, octopuses, and other animals of particular concern do not engage in sensation seeking or play?”)
EDIT: I don’t think I had the right idea of what sensory play is. Sensory play seems to be a kind of exploratory play directed at things with novel or unusual sensory properties, like sand, bubbles, squishy things, different sounds, different smells, etc..
This and this, where fish are thrown into the water and come back and thrown again, also looks like sensory play (unless I’ve misunderstood what Humphrey meant). But, there might be other explanations, e.g. maybe the fish aren’t coming back to be thrown again, but because they’ve been trained to, or because they want something else. It doesn’t seem like something they’d specifically have been evolved to be motivated by this, given how unnatural it is.
There’s also this study of ball-rolling in bumble bees that the authors conclude meets the criteria for play:
Here, we show that rolling of wooden balls by bumble bees, Bombus terrestris, fulfils behavioural criteria for animal play and is akin to play in other animals. We found that ball rolling (1) did not contribute to immediate survival strategies, (2) was intrinsically rewarding, (3) differed from functional behaviour in form, (4) was repeated but not stereotyped, and (5) was initiated under stress-free conditions.
No studies of carp could be found. An anecdotal observation of possible play was described in two other cyprinid species, the redeye (Scardinius erythrophthalmus) and the rudd (Leuciscus cephalus), showing that these fish returned over and over for the experience of being thrown out of the water by a human hand and the fish often competed vigorously to be the next one to be thrown (Burghardt, 2005). Burghardt (2005) provides a review of a large body of anecdotal evidence that suggests that play may exist in multiple species of teleost fish. However, further empirical studies involving controlled and systematic observation of fish play behaviors are needed and could follow up on the anecdotal observations outlined by Burghardt (2005). Importantly, the current lack of documented play behavior in fish may not indicate that fish do not play but rather that they are too uncomfortable in the typical housing we provide for them to engage in play (Fife-Cook & Franks, 2019). Thus, further research requires housing fish in environmental and social conditions conducive to a relaxed state (Fife-Cook & Franks, 2019).
It is common for juvenile and adult salmonids to jump into the air from the water, and this behaviour is highly relevant in salmonid net-pen culture and may be related to buoyancy regulation, parasitic infections, or stress (Fagen, 2017). However, Fagen (2017) has suggested that some jumping behavior seen in Atlantic salmon (Salmo salar) may represent a form of locomotor play but calls for additional research. Burghardt (2005) also reports on anecdotal observations of possible instances of locomotor play (not involving jumping) resembling adult redd-digging behavior in juvenile Coho salmon (Oncorhynchus kisutch). Burghardt (2005) provides a review of a large body of anecdotal evidence that suggests that play may exist in multiple species of teleost fish. However, further empirical studies involving controlled and systematic observation of fish play behaviors are needed and could follow up on the anecdotal observations outlined by Burghardt (2005). Importantly, the current lack of documented play behavior in fish may not indicate that fish do not play but rather that they are too uncomfortable in the typical housing we provide for them to engage in play (Fife-Cook & Franks, 2019). Thus, further research requires housing fish in environmental and social conditions conducive to a relaxed state (Fife-Cook & Franks, 2019).
Play behaviour has frequently been reported in octopuses. In captivity, octopuses are eager to explore inanimate objects (e.g., Lego, balls); they carry them around their aquarium tank and pass them from arm to arm (Kuba et al. 2003; Kuba & Byrne 2006). Giant Pacific octopuses, Enteroctopus dofleini, manipulate floating objects (e.g., plastic bottles) by squirting jets of water at the item, sending it to the far end of their aquarium and repeating the behaviour when the object floats back to them (Mather & Anderson, 1999). In the wild, different species have been observed collecting and manipualting different objects such as plastic and glass bottles (Mather 1994).
Humphrey spent a lot of time saying that authors like Peter Godfrey-Smith (whose book on octopus sociality and consciousness I have read, and also recommend) are wrong or not particularly serious when they argue that octopus behavior is play, because there are more mundane explanations for play-like behavior. I can’t recall too much detail here because I no longer have Humphrey’s book in my possession. In any case I think if you convinced him octopuses do play he would probably change his mind on octopuses without needing to modify any aspects of the overall theory. He’d just need to concede that the way consciousness developed in warm blooded creatures is not the only way it has developed in evolutionary history.
Actually, I have to correct my earlier reply. Iirc the argument is that all conscious animals engage in physical play, not necessarily that all playful animals are conscious. On the other hand, Humphrey does say that all animals engaging in pure sensation-seeking type play are conscious, so that’s probably the sort of play he’d need to bring him around on octopuses.
Upvoted because I’m a fan of people summarizing and signal-boosting literature that bears on EA priorities. Disagree-voted because I’m not convinced that any of the observations or considerations put forward support the headline claim that only mammals and birds are sentient.
Also, I’m pretty sure that octopuses do play? A quick search appears to confirm this: “Octopuses like to play” (BBC).
I mention this in response to the part of the post that reads: “Other animals like fish, reptiles, and octopuses do not engage in sensation-seeking or play and so do not have those internal conscious experiences.”
(ETA: I see that in their closing section, OP acknowledges some uncertainty here, listing as a question for further investigation: “Is it really true that fish, shrimp, octopuses, and other animals of particular concern do not engage in sensation seeking or play?”)
EDIT: I don’t think I had the right idea of what sensory play is. Sensory play seems to be a kind of exploratory play directed at things with novel or unusual sensory properties, like sand, bubbles, squishy things, different sounds, different smells, etc..
This and this, where fish are thrown into the water and come back and thrown again, also looks like sensory play (unless I’ve misunderstood what Humphrey meant). But, there might be other explanations, e.g. maybe the fish aren’t coming back to be thrown again, but because they’ve been trained to, or because they want something else. It doesn’t seem like something they’d specifically have been evolved to be motivated by this, given how unnatural it is.
There’s also this study of ball-rolling in bumble bees that the authors conclude meets the criteria for play:
Rethink Priorities collected some evidence of play behaviour across species. From their Welfare Range Table (EA Forum post):
Humphrey spent a lot of time saying that authors like Peter Godfrey-Smith (whose book on octopus sociality and consciousness I have read, and also recommend) are wrong or not particularly serious when they argue that octopus behavior is play, because there are more mundane explanations for play-like behavior. I can’t recall too much detail here because I no longer have Humphrey’s book in my possession. In any case I think if you convinced him octopuses do play he would probably change his mind on octopuses without needing to modify any aspects of the overall theory. He’d just need to concede that the way consciousness developed in warm blooded creatures is not the only way it has developed in evolutionary history.
Actually, I have to correct my earlier reply. Iirc the argument is that all conscious animals engage in physical play, not necessarily that all playful animals are conscious. On the other hand, Humphrey does say that all animals engaging in pure sensation-seeking type play are conscious, so that’s probably the sort of play he’d need to bring him around on octopuses.