Feature lists:

List 1: “essential consciousness (level 1)”. I suggest these are the core features of consciousness, common to all conscious creatures on planet earth.

List 2 : “Level 2 consciousness”. Level 2 consciousness is a higher consciousness, present in most humans and, likely some other mammals. Level 2 is qualitatively different from level 1 and some consider it to be true “conscious”. I’ve taken the approach of distinguishing two levels. My dogs are conscious, but not level 2.

List 3: “Biological Features Connected to Consciousness” A speculative list of behavioral and structural features whose evolution may be tied to consciousness.

The goal of lists 1 and 2 is to recognize essential features of consciousness, not to explain it. No mechanisms are included. I hope, however, that the lists will help understand what consciousness is good for, and how the features of consciousness offer adaptive advantage. They are also intended to elicit criticism and discussion. Personal blog format seems appropriate for informal presentation and discussion.

I apologize in advance for lack of citations. Putting in citations would transform this from a brief to a long project. In most cases I’ve lost track of the origin of a feature, or how it’s been expanded. In order to avoid poor citations, I have, for the most part, given none. I don’t want to imply that they are self-generated, although I’ve worked on them for awhile.

The elements of the lists are not isolated; many are interdependent. The sequence in each list is not arbitrary, but not carefully considered.

Essential Consciousness (level 1):

1. Agency. the ability to act on the environment. Critical. Some feel that “locked-in syndrome” argues against agency being a critical feature. The counter argument is that individuals with locked in syndrome lived a life with agency before the precipitating event. The agency criterion leads to the notion that robots, but not computers, could attain consciousness.
2. Sense of ‘self’ and boundary between self and environment. That is, a conscious entity can differentiate what is inside (of self) and what is external. Self is the first discrete object (see “discrete entities“, below)
3. Subjectivity. Conscious experience is ‘egocentric’, centered on self in a location in time and space. In addition, self-world interactions are part of agency.
4. A life. A conscious individual is at least somewhat aware of self extending from the past through the present and into the future. I’m calling this trajectory of self through time “a life”. A second characteristic of “a life” is that spatial location and time are continuous. No jumps in the space-time trajectory. “A life” may be identical to personal identity.
5. Discrete entities. After the individual ‘becomes conscious” by separating self from non-self (universe) the conscious individual identifies discrete things, objects, in the universe. These may be rocks or clouds or people or institutions or events. Searle argues that discrete things only exist in a conscious mind. Without a conscious mind, they are only organized collections of atoms (or subatomic particles). Conscious minds generalize the patterns of organization and call them objects. This is a remarkable claim. In my reading of this — with modest extension — all things we refer to as ’emergent properties’ are products of the mind, and are not essential features of the natural world.
6. Happiness as an inner state. The conscious individual must have a value system, a way of differentiating actions to take and to restrain. Happiness is the core of all value systems.
7. Autobiographical memory. This is related to a concept of ‘a life’. Also related to a concept of events occurring in the future. But the requirement for ‘memory’ puts computational constraints on a conscious system. (memory does not need to be accurate). update: perhaps this should be “episodic memory”. The key idea is there must be memory for personal (self) interactions with the world, for a concept of ‘self’ to exist.
8. Sense of space and time. The ‘a life’ concept requires this. My guess is that these are a priori concepts (Kant). A conscious entity has a mind born with these framework concepts; they cannot be leaned.
9. The global reference frame is an allocentric world frame. As we move through space the world does not move around us, but we move through the world. If you tilt your head, the world does not rotate. Although our point of view is egocentric it exists within an allocentric global reference. This is complicated. It seems to contradict ‘egocentric’, above, and partially does. Self-motion is a special case. My guess is that ‘subtracting self motion’ is very primitive and common to most animals.(this entry is a dec 26 update; not on early versions of this list)
10. Unity. Conscious awareness is a unified, one-at-time process. Although we know the brain does many things in parallel, the conscious aspect of mental activity does not work that way. The concept of unity comes from everyday experience and psychological experiments, but it also makes sense. Unified awareness permits a unified sense of self, an essential feature of consciousness. The connection of unity to the conscious experience was pointed out in John Searle’s recent article in the NYRB (most of the article behind firewall).

Level 2 consciousness:

1. Theory of mind — the awareness of consciousness of others. I’d argue that this is part of level 2 consciousness.
2. Birth and death and awareness of space time existing before birth and after death. This is an extension of “A Life”, above
3. Language. Some argue that symbolic representation is essential for consciousness. I argue that it is essential for level 2 consciousness. My dogs are conscious.

Biological Features Connected to Consciousness. On planet earth several features that emerged in the evolution of animals seem intimately related to conscious processing.

1. The eye and visual brain. These are responsible for direct awareness of 3D space in an egocentric frame. Other sense modalities, such as audition or echolocation, may contribute to 3D perception of space, but vision is primary and got there first. All sense modalities, when combined with self-motion cues (see locomotion, below) can aid. But vision — the eye, not photodetection — is a spatial sense that organizes self-environment relations. Fascinating introduction to the significance of the evolution of the eye during the Cambrian explosion found in Andrew Parker’s In the Blink of An Eye.
2. Locomotion. Two points: All of the organisms that I suspect are conscious locomote. And the essential, Kantian notion of space leads to the ability of a self to have different locations in space. My guess is that all vertebrates and many invertebrates have a recognizable form of consciousness. I have doubts about plants and single-celled animals. Virtually all of the organisms I suspect having consciousness locomote. (This is a circular argument, but worth considering. This project is based on intuition, not formal logic.) There appears to be an intimate connection between locomotion and vision.
3. A clock. Necessary for organizing autobiographical memory. Not clear how this is implemented. Brain mechanisms for memory, especially episodic memory.
4. Emotional states. Related to happiness and a unified value system.
5. Self-motion Subtraction System. Probably Vestibulo/Visual/Cerebellar

Final Note: As a neuroscientist, not a philosopher, these lists are not in my comfort zone. I hope they are useful. They’ve been fun to compose on Christmas day.