A Miniature: Panpsychism & Monism

What is the argument for panpsychism? Is it this? -

1. Since there is consciousness in the complex parts of the world, and
2. the complex is only a sum of simple parts, it must follow that
3. there must also be consciousness in the simple parts of the world.

Premises i and ii seem intuitively true. However, is iii a correct conclusion to premises i and ii? Is it, in fact, true?

There is indeed “consciousness in the complex parts of the world”. For instance, in the brains of human beings (if ‘in’ is the correct word here). And many people agree that consciousness is a result of some level of complexity.

How complex must something be in order to bring about consciousness? Human beings, for example, have billions of neurons in their brains. Ants have, say, tens - or hundreds - of thousands of neurons in their brains. Is this enough to bring about consciousness? Or is there more to this story than simply counting how many neurons a creature has?

If a creature had trillions of neurons, would it be ultra-conscious (or have ultra-consciousness)? And need that complexity only be the complexity of neurons and other aspects of the human brain?

What if we connected a thousand computers up together and programmed them to work as one? If that could be done, then would that large-scale and complex integration automatically bring about consciousness? Alternatively, is it an a priori truth that something simple (like an earthworm or even a pencil) can’t be conscious?

As for premise ii). Yes, it would seem to be the case that “the complex is only a sum of simple parts”. (Indeed the complex must be a sum of simple parts otherwise it wouldn’t be, well, complex.) However, what about the word “only” - as in “only the sum”? Perhaps there's more to a complex machine, creature or thing than simply the addition of simple parts to one another in order to create a complex whole. Perhaps something emerges from the addition of simple parts. Is a nation state, for example, only the sum of its parts? Is a class or set only the sum of its members? Is mind or consciousness only the sum of the parts of the brain (as well as, perhaps, other physical things)?