Chris Fields Research

Chris Fields Research
Ideas, drafts, recent publications ...

Atenas, Costa Rica
Caunes Minervois, France
Santa Fe, NM, USA

Photo: Kym Yorke

Objects and "Emergence"

We all experience the world as composed of objects - tables, chairs, cars, books, plants, animals, each other - that persist through time. Our language is full of words that refer to such objects, and we all know, at least in a rough-and-ready, practical way what these words mean: we can all use words like "table" or "car" successfully in a conversation. We are able, in practice, to distinguish things like chairs or books from all the other stuff that we experience, and we know that we can pick up a book, for example, and move it two feet to the left without it ceasing to be the book we picked up and turning into something else. We learned these kinds of basic facts about the world as infants, some of them before and some while we were learning our native languages. Our earliest accessible memories are memories involving objects, memories that we can recall as images of objects and describe using words that refer to objects. Experiencing the world as made up of individual objects is, moreover, not voluntary. We don't choose to experience the world as composed of separate, movable, persisting objects: that's just the way we experience it.

I am interested in three questions about our ordinary experience of a world composed of individual, persisting objects. First, how do we do it? How do we distinguish a particular object from everything else, from the "environment" that surrounds it? And how, once we have distinguished an object from its environment, do we judge whether it is the same object that we remember encountering at a previous time? How, for example, do we distinguish our car from all the other stuff around it, and how do we identify it as our car, the same one we had two hours ago? Finally, I'm interested in how we came to be able to distinguish objects from their environments, and to regard them as persistent through time. This question clearly has two components: one that asks how an individual person develops these abilities during infancy and early childhood, and one that asks how human beings or other species developed these abilities over evolutionary time.

Underlying these questions about human abilities, or the abilities of other organisms, is the question of whether we can explain the objects of our ordinary experience in terms of our fundamental science. Human beings have developed astoundingly accurate and useful fundamental sciences. The most accurate is fundamental physics, the quantum physics that describes the invisible world of "elementary" entities and forces. Using this science, we can predict the properties of entities like electrons, construct extraordinarily sensitive instruments to test our predictions, and discover that our theoretical predictions are correct to within one part in 10 billion. We have surrounded ourselves with artifacts that we can build only because we understand quantum physics: digital cameras, for example, and laptop computers. It has been a working assumption of fundamental science for over a century that it - science - also correctly accounts for the objects of our ordinary experience, that given enough time and trouble one could, for example, use quantum mechanics, atomic physics, basic chemistry, and so on to explain what it is to be a chair - or at least, what it is to be a chair-sized macroscopic object - in the same way that one can explain what it is to be an electron or an atom of uranium. This working assumption is sometimes stated as the claim that the "classical" world of ordinary experience, so called because it is at least approximately described by "classical" Newtonian physics, "emerges" from the underlying quantum world of fundamental entities and forces. Claiming that the classical world emerges from the world described by fundamental science is one way of claiming that it exists completely independently of our observations, that it can be taken for granted, for example, that the Moon is there (as Einstein famously put it) even if no one is looking at it.

I would like to understand whether the claim that the classical world emerges from the quantum world is true, and if so, how this emergence works. Here again the question has two components. One is whether, and if so how, a classical description of the universe or some relevant part of the universe can be derived as a theoretical consequence of a quantum description of either the universe as a whole or the relevant part. This is an "in principle" question, as the computational complexity of actually deriving even the state of an atom from the equations describing its components is overwhelming. It has, however, practical consequences, as it is the question of whether quantum physics completely accounts for the classically-appearing behavior of macroscopic objects, such as laptop computers or human bodies, that are known to operate according to quantum theoretic principles. The second question is whether, and if so how, a cosmological account of the evolution of the universe can be given in quantum-theoretic terms. This is also a practical question, as such accounts are proposed, at least in approximate form, to explain the emergence of classically-appearing space, time and matter from the quantum state of the universe immediately following the Big Bang.

The boundary project

The questions about how people perceive objects and about whether objects can be regarded as emergent are clearly related. It is much easier to contemplate understanding how people experience a world of independent, persistent objects if one supposes that such objects objectively exist, that they are there to be experienced, completely independently of us. The idea that the world we experience emerges from the interactions between electrons, quarks, photons and the like is a way of making this supposition of "actual, independent reality" concrete. Were this idea to turn out to be wrong, or more prosaically, were it to turn out that our current theoretical methods are not sufficient to demonstrate the emergence of the classical world of ordinary experience from the quantum world, we would be faced with the prospect of trying to understand our perception of the classical world without any theory to explain what the classical world is or where it comes from. One way to investigate these issues is suggested by the fact that the objects of ordinary experience are spatially bounded: it is clear where they begin and end, what is part of them and what is not. One can, therefore, ask how we perceive the spatial boundaries of ordinary objects, and the related question of whether those spatial boundaries can be predicted from fundamental physics. The first of these questions is a concern of cognitive psychology, and in particular cognitive neuroscience. The second is a concern of quantum mechanics, and in particular the basic quantum mechanics of ordinary-sized objects moving at speeds much less than the speed of light.

The boundary project explores these two questions in parallel. One research track considers results from cognitive psychology experiments that examine the conditions under which people visually identify objects as being "the same thing" even though their locations, visibility, and surface features change, and results from functional neuroscience experiments that explore the implementation of these identification abilities in the brains of humans and other species. The goal of this track is to understand how people visually distinguish objects from their environments, and how they judge whether what they are seeing now is "the same thing" as what they saw a few seconds, a few hours, or a few years ago. The second research track considers the question of whether the perceived boundaries of ordinary, macroscopic (i.e. large compared to atoms) objects can be predicted from the quantum physics of the microscale. The goal of this track is to understand whether, and if so how, the boundaries of objects that we see emerge from descriptions of collections of fundamental entities that are formulated using the most precise, accurate, experimentally validated and technologically productive physical theory that is currently available.

More on the psychology of boundaries ...