Scientists propose a new, improved way to help researchers discover when consciousness emerges in human infancy. When in the developmental process do people become conscious? When 17th-century French philosopher René Descartes was asked by his critics about the consciousness of babies, he eventually suggested that babies’ thoughts may be simpler than those of adults. Hundreds of years later, the question of when humans became conscious remains a problem for psychologists and philosophers alike.

But now, in response to a recent article Trends in Cognitive Science Two scientists from the University of Birmingham have proposed an improved way to help scientists and researchers determine when babies become conscious.

Also published in his letter to the editor Trends in Cognitive Science Associate professor of philosophy Dr. Henry Taylor and developmental psychology professor Andrew Bremner explored a proposed new approach that involved identifying markers of consciousness. It is measured in adults and later in babies’ developmental stages when they begin to show more of these.

“For example, imagine that we knew that a certain very specific behavior or a certain pattern of brain activation in adults always comes with consciousness,” Taylor says. So, if we can identify when this behavior or brain activation occurs in babies, we have good reason to believe that this is when babies develop consciousness. “Behaviors and brain activations like these are what we call ‘markers’ of consciousness.”

This approach is important because children (unlike adults) cannot tell you what they are aware of. Professor Bremner said: ‘It is really difficult to determine when babies become conscious. This is largely because babies cannot convey their experiences and, as most parents know, they can be quite stubborn, especially when it comes to experimental tasks. Since we cannot simply ask babies when they become conscious, the best approach is to try to identify a wide range of markers of consciousness that occur early and late in development and then group them together; “This could help us determine when consciousness arises.”

Re-evaluation of markers of consciousness

In a recent paper, researchers (Professor Tim Bain and colleagues) proposed four specific markers of consciousness, some present in late pregnancy and others in early childhood. Based on this, the study claims that consciousness emerges early (from the last prenatal trimester).

But Professor Bremner and Dr Taylor say this ignores other signs of consciousness. Previous studies have identified a distinct set of markers. They include:

• Guidance (drawing and controlling the social partner’s attention to the topic).
• Intentional control (intentional coordination of actions between means and end – for example, pulling a prop to retrieve a distant object).
• Explicit memory (delayed imitation of actions).

Expanding the research framework

Dr Taylor said: “One of the difficulties is that not all markers for the onset of consciousness appear to point to the same age. The data cited by Bain and colleagues point to a period between the third trimester of pregnancy and early childhood, but other indicators suggest this age may be closer to a year.” “In fact, at the extreme, some signs only appear after 3-4 years. It is extremely difficult to draw a conclusion because there are so many different markers of consciousness that appear in the early and late stages of development.”

Professor Bremner concluded: “We believe that a broad approach to markers is required, including those that emerge at early and late stages. We also recommend that a range of developmental models of the emergence of consciousness be considered. For example, some markers emerge in a cluster at early stages of development.” others may appear in a later cluster, and there may be a persistent and gradual emergence of certain markers during pregnancy and early life.

“By bringing together such a variety of signs, we believe we can finally answer a question that has puzzled us for thousands of years. But it is important to keep in mind that the answer may not be simple!”