An ongoing controversy in philosophy is whether or not we can provide an evolutionary account of consciousness. Can we say that consciousness (i.e., our subjective phenomenal experience) evolved for a particular reason that gives conscious organisms an adaptive advantage? This question may seem to have an obvious answer: yes, of course consciousness is important, we wouldn’t be the complex organisms that we are without it. But if you examine how consciousness interacts with other functions of the brain and behavior, its actual utility becomes questionable and could be seen as either a random byproduct of brain activity (a form of subjective illusion) or a feature of cognition with no proper evolutionary purpose that results from the combination of other functions (a “spandrel”). So, to better understand what consciousness is, it is important to outline its possible evolution.
First, let’s consider the relationship between consciousness and attention (a relationship we have been exploring for a while now). Various studies have shown that the selective information processing associated with attention can occur outside of consciousness. Attention often operates in the background, allowing us to interact with the environment without much thought, and it can bias us to make certain decisions without us being aware of it. We need not be conscious of this attentive processing for it to influence behavior — that’s why we can navigate effortlessly around our home and that’s how marketing works its magic.
There are cases where what we perceive does not match what is actually in the world, take visual illusions for example. Yet even when our perception is deceived, we can act properly on the object that deceived us. This was shown through studies where a visual illusion (based on the common Müller-Lyer illusion) causes the subject to incorrectly perceive lines to be a certain size but when making physical actions to those lines, the subject performs accurately. In other words, the visual information sent to the motor system is correct while the information reaching conscious awareness is not quite perfect (e.g., see Stöttinger & Perner, 2006). More extreme examples include blindsight, where damage to a specific part of the visual cortex can prevent the experience of visual consciousness but yet the individual can act on objects in front of them even though they claim that they cannot see these objects (see Kentridge, Heywood, & Weiskrantz, 1999).
These and other examples of attention with inaccurate or no conscious experience, which nevertheless result in relevant behaviors, give support to the consciousness-attention dissociation that we have been discussing (see our first blog post). But there are also important cases when we are aware of paying attention. Take the example of learning a new complex skill like playing the piano. When you first start learning to play, it requires a voluntary, deliberate, and an effortful sort of attention. In such cases of learning a complex skill, it certainly feels like conscious experience is essential (but this experience of effort can change and become automatic and effortless with expertise).
Still, can we confidently say that consciousness evolved for any particular reason? Attention, on the other hand, clearly evolved to facilitate how organisms initiate motor commands to interact with their environment, especially as their interactions grew more complex. The research on attentional systems found in the basic neural structures of organisms has detected attention in a range of species, from insects to primates. For example, studies have identified the neural mechanisms of feature-based selective processes in dragonflies (e.g., see Wiederman & O’Carroll, 2013). Crows can use tools, and this problem-solving requires top-down goal-oriented attentive processing (see this website for more details on crows and other animals). Furthermore, one can speculate that animals with capacities for episodic-like memory (e.g., scrub jays) may possess feature recognition and event-based attention, but we need more empirical work to support such claims about complex attention in animals.
Nevertheless, it’s not that difficult to see the adaptive evolution of attention since it appears in several forms with varying complexity. From these forms of attention and their increasing complexity, one could outline the evolution of attention based on adaptations that were required as environmental challenges increased — such a theory would not cause much controversy (see the figure below with proposed timeline). Describing the evolution of consciousness, however, is more controversial. But if we look at the overlap between consciousness and attention — conscious attention — this approach could provide a way to describe an aspect of consciousness that has evolved for a reason, for example, by providing a way to attend to motor schemas without acting on them (Graziano, 2014). So we need to study cases of attentive processing that require a certain level of conscious awareness and explain how the brain adapted to produce those forms of attention.
In terms of simple conscious attention, there is the ability to report information from basic selective attention, such as feature-based and spatial attention. Examples of more complex forms of conscious attention include cross-modal attention, attention to conceptual content, and a voluntary form of attention that requires a deliberate and sustained deployment of focused attention on a specific feature, object, or task. Now if we were to speculate what purpose conscious attention might serve, it could include the following:
Such cases of attention appear to be recent adaptations in the brain, as they seem to rely on the “newer” brain areas (e.g., the frontal cortex). These abilities appeared in organisms that have more complex social environments, far more complex than the basic attentive processing found in insects. Abilities like empathy, for example, would not be possible without conscious attention — an ability that is crucial for species with social interactions. These are all forms of conscious attention that need to be examined more closely from the perspective of trying to understand the adaptive purpose of conscious attention, which is still unclear because many forms of attention can happen outside of awareness (see Haladjian & Montemayor, 2015).
Although we do not have a clear understanding of consciousness, focusing on conscious attention may help us solve some of the mystery of consciousness. A critical topic for research in this area is the relation between language and symbolic conceptual attention. If the claim is substantiated that syntax for symbolic language is unique to Homo sapiens (Chomsky, Hauser & Fitch, 2002), and if the type of symbolic conceptual attention required in many conscious attentive routines is essentially linguistic, then that would potentially bring the evolution of that kind of attention to as recently as 200,000 years ago. This would be an extremely recent type of conscious attention. Similar considerations apply to attention to the mental states and plans of others, although this is more controversial.
Once we identify the adaptive purpose of conscious attention, particularly for cases that require the conscious aspect of attention, we can ultimately better understand what brain systems support consciousness and what purpose it may have.
- Harry Haladjian & Carlos Montemayor
Haladjian, H. H., & Montemayor, C. (2015). On the evolution of conscious attention. Psychonomic Bulletin & Review, 22(3), 595-613.
Hauser, M. D., Chomsky, N., & Fitch, W. T. (2002). The faculty of language: What is it, who has it, and how did it evolve? Science, 298(5598), 1569-1579.
Kentridge, R. W., Heywood, C. A., & Weiskrantz, L. (1999). Attention without awareness in blindsight. Proceedings of the Royal Society B: Biological Sciences, 266(1430), 1805-1811.
Montemayor, C., & Haladjian, H. H. (2015). Consciousness, Attention, and Conscious Attention. Cambridge, MA: MIT Press.
Stöttinger, E., & Perner, J. (2006). Dissociating size representation for action and for conscious judgment: Grasping visual illusions without apparent obstacles. Consciousness and Cognition, 15(2), 269-284.
Wiederman, S. D., & O'Carroll, D. C. (2013). Selective attention in an insect visual neuron. Current Biology, 23(2), 156-161.