This could be a very long post, but isn't -- surely a few other short ones and a longer one will follow this summer. If you've been following, you will remember that I'm beginning to ramp up for my fall course on biology of mind.
Consciousness, of course, is one of the most difficult issues, because there is so much disagreement about what it actually is and how it relates to other mental functions. In that vein, this paper by Seth and colleagues is useful, because it compares and contrasts 17 different criteria for consciousness and their consequences as applied to humans and other mammals. They range from baseline (EEG readings) to long-term observational ("consciousness facilitates learning"). Here is the abstract:
The standard behavioral index for human consciousness is the ability to report events with accuracy. While this method is routinely used for scientific and medical applications in humans, it is not easy to generalize to other species. Brain evidence may lend itself more easily to comparative testing. Human consciousness involves widespread, relatively fast low-amplitude interactions in the thalamocortical core of the brain, driven by current tasks and conditions. These features have also been found in other mammals, which suggests that consciousness is a major biological adaptation in mammals. We suggest more than a dozen additional properties of human consciousness that may be used to test comparative predictions. Such homologies are necessarily more remote in non-mammals, which do not share the thalamocortical complex. However, as we learn more we may be able to make "deeper" predictions that apply to some birds, reptiles, large-brained invertebrates, and perhaps other species (Seth et al. 2005:119).
There are few conclusions, mainly just a description of properties that ought to receive more attention in relationship to each other and to consciousness.
Seth AK, Baars BJ, Edelman DB. 2005. Criteria for consciousness in humans and other mammals. Consciousness and Cognition 14:119-139. DOI link