To be honest a lot of this stuff is pretty easily answered and has been discussed ad nauseum in spaces like /r/vegan. This is also not a great space to ask this question of vegans, as a lot of carnists (yes that includes vegetarians) come here to argue against veganism and upvote answers they agree with but that practicing ethical vegans are likely to reject. You are likely to get better answers from vegans in other spaces.

In terms of your above post there is nothing scientific in what you’ve described. It appears you are using a veneer of science to avoid adopting views you disagree with. To be frank there is a lack of research on almost all animals in terms of their sentience, intelligence and capacity to suffer, presumably due to the carnist nature of society. There is also the unavoidable philosophical problem of other minds, which we are unlikely to be able to readily solve with science; we will never truly be able to determine the experience of another non-homo sapien creature and can only work through analogy to the experience of homo sapiens.

The above notwithstanding, even if some creatures are more “intelligent” in some ways than other creatures, how does this impact their entitlement to the bare minimum of moral consideration, i.e. freedom from intentional harm and exploitation? How have you determined that each “tier” that you have created only deserves the rights you have designated? The assignment and exclusion of moral consideration is the province of philosophy and politics, not science. There are certain classes of humans who are alive, and through severe disability or illness, have intelligence arguably lesser than many of the animals listed above in your lower tiers. Would you therefore exclude them from moral consideration? Of course not, and this is why intelligence is irrelevant to moral consideration - it is not a morally relevant characteristic.

The morally relevant characteristic that stands philosophical rigour to determine if moral consideration should be granted is a capacity to suffer. It is pretty clear that all of the animals listed, apart perhaps from tier 5, have this, so it makes sense for these animals to have moral consideration.

You have also completely ignored the well established link between commodification and carnism in the above, which is a key reason, as to why exploitation and commodification of animals is ethically unacceptable and should be eschewed - the commodification of animals, or relegation of them to zoe, is fundamentally how we as a society and as individuals justify their ongoing torture, mistreatment and slaughter in most ways throughout society. This is without even going into other issues regarding exploitation, such as an inability for an animal to provide meaningful consent, and respect for bodily autonomy that we grant other individuals, regardless of intelligence.

This doesn’t mean that vegans would generally be opposed to adopting animals to care for them, or opening sanctuaries - most people I have encountered and literature I have read understand that we operate within the internal logic of a carnist society, and that while it is unethical to engage in the support of further breeding, it is ethical to care for adopted animals (or animals you had prior to going vegan) that have already been brought into existence through this system.

In terms of your tier 5, due to the lack of research here, the problem of other minds, and the lack of necessity here for people to engage in the exploitation or harm of these creatures, I am of the view that the default position should be erring on the side of caution.

I find it kind of funny that you’re sitting there and arbitrarily deciding the rights of different species based on what brain you think they have. The truth is, at this point in time, no one knows to an exact science how any species thinks, or feels for that matter regarding pain, and so the idea that you’re taking a scientific approach here should be met with skepticism at best.

I don’t really understand what’s so hard to understand about “cause no animal harm”. The act of segregating species and giving different ones different rights because you maybe feel like eating insects isn’t any different to why people aren’t vegan today. I mean look at how religion justifies eating fish when no other meat should be eaten for example.

Intellect is a red herring.

Jeremy Bentham understood this 200 years ago: “The question is not, Can they reason?, nor Can they talk? but, Can they suffer?”

As a thought experiment, ask yourself if you would be happy to harm a mentally-disabled human being simply because of their cognitive deficiency.

Almost 25 years vegan here. I don’t really gaf about bugs. I murder ants by the thousand when they invade my house, I slap mosquitos without remorse… but I will save spiders from the bath.

The only animals that deserve to be in a lower tier are mosquitos and wasps.

I just find it easier to err on the side of not harming these animals. There’s so many criteria, you may want to consider for morality when you do go into that.

For example, insects are currently rapidly dying and this will likely fuck humanity over in a decade or two.
Breeding+farming insects presumably won’t impact that. Squatting singular flies basically won’t impact that. It’s climate change and pesticides that are the culprits here.
But it’s an example where your metric of mental complexity doesn’t reach far enough. We do need to protect simple animals, too.

Of course, on the other side of that discussion, if we don’t use pesticides, we may not be able to feed all humans. There’s a lot of nuance to that discussion and there may not be an easy side to pick after all, but yeah, that complexity is why I prefer to err on the morally simpler side.

I should also add that this is what I live by, I generally don’t impose it on others, because of this incompleteness in my reasoning.

If you’re vegan enough to affect your market decisions, welcome to the making things better club.

Nobody is the vegan police checking to see who’s doing the best. Decide why you want to be vegan or not and then live accordingly.

Veganism is not eating animal products. That’s it. It’s not a religion, so believe what you want.

If you want to be a non-vegan conscientious eater with a diet based on your internal ethics, please do. You don’t need a title.

That said, I’m vegetarian, so I’m probably wrong