Newswise —

Humans have consciousness. However, is it just a result of evolution or does it serve a crucial purpose? Professors Albert Newen from Ruhr University Bochum, Germany, and Carlos Montemayor from San Francisco State University, USA, propose a fresh theory to address this issue. They identify two tiers of consciousness, each with two distinct roles, in the January 1, 2023 edition of the Journal of Consciousness Studies.

The initial phase of consciousness is fundamental arousal, and the subsequent phase is broad vigilance. "These phases correspond to two fundamental functions that are interdependent," explains Albert Newen of the Bochum Institute for Philosophy II, elucidating why he rejects the notion of consciousness as an incidental byproduct of evolution. As per the alarm hypothesis, primary arousal developed throughout evolution to induce a state of alarm in the body, which helped maintain the organism's existence. This occurs when critical life functions, such as respiration, nutrition, or temperature control, are disrupted abruptly, and survival is at risk.

Basic arousal puts organisms into a state of alarm

Carlos Montemayor illustrates, "When we expose ourselves to scorching summer heat, we begin to sweat automatically. Normally, such gradual, involuntary adaptations are adequate to maintain our body temperature. They occur unconsciously." He continues, "However, if we abruptly enter an extremely hot environment, these gradual adjustments are no longer sufficient. The organism is at risk of being harmed, for instance, by sunburn. Typically, the body reacts with a pain signal that puts us in an alert state, prompting us to take immediate action." Reflexes such as avoidance and escape are activated when sudden pain arises. Thus, fundamental arousal has the fundamental function of triggering an alarm state in a biological organism, halting all gradual adaptation processes like sweating and initiating a swift avoidance and escape reaction that preserves life. Basic arousal, spurred by pain, endures and ensures that individuals care for their body beyond the initial reflex response.

General alertness enables new behaviours

Newen and Montemayor propose that humans and several animals have also developed general vigilance based on this mechanism. It facilitates various forms of learning that require focused attention. If the body is alarmed, organisms can employ general alertness not only to activate reflexes but also to initiate novel actions. Newen elaborates, "For instance, it assists us in comprehending that the threat of fire can be eliminated not only by running away, but also by employing a fire extinguisher in some situations."

Newen and Montemayor derive evidence for their theory primarily from two animal studies conducted by experimental research groups. In one study from 2020, led by Yuri Saalmann at the University of Wisconsin, macaques were anesthetized, similar to humans undergoing surgery. In this state of unconsciousness, the researchers selectively stimulated a particular region in the brain, the central lateral thalamus. As soon as the stimulation was applied, the macaques became conscious. When the stimulation ceased, they returned to an unconscious state. "The stimulation acted as a switch to trigger consciousness," explains Carlos Montemayor. However, it only prompted fundamental arousal because the macaques could feel pain, see things, and react to them, but they were unable, unlike regular wakefulness, to participate in learning tasks.

Crucial role of the thalamus

A second experiment, conducted by Michael Halassa at the Massachusetts Institute of Technology, provides additional evidence that mice possess general wakefulness in their daily lives. The animals were trained to respond to a sound differently than to a light signal. They were also capable of interpreting a third signal that indicated whether they should focus on the sound or the light signal. "Given that the mice learned this quickly, it is clear that they have acquired learning with focused conscious attention and, therefore, possess general vigilance," concludes Albert Newen. Other regions of the thalamus, notably the activation of a central area called the nucleus reticularis, were significantly involved. The alarm theory of consciousness fills a gap in major rival theories of consciousness, such as the global workspace theory of the brain and the information integration theory, which assign only a minor role to the thalamus.

Humans also have reflexive self-consciousness, which is the ability to reflect on oneself, one's past, and one's future. "Whether some animals have basic forms of reflexive self-consciousness is still an open question," says Newen. "This type of consciousness will be explored in future research."

Journal Link: Journal of Consciousness Studies, 2023