During each moment, a vast amount of different stimuli reach our senses – sounds, sensations, and objects in the field of view. Since the capacity of our attention is limited, we only processes a small fraction of them. So what happens to the stimuli that reaches our senses, but do not get access to our consciousness?  Can they influence our behavior without our knowledge and control?

Research currently being carried out at the Nencki Institute of Experimental Biology, PAS aims to learn about the capabilities of our “unconscious mind.”  The investigated processes are often described as “subliminal”, as they occur before the threshold of consciousness. We’ve known for a long time that our brain is capable of subliminally processing and analyzing different types of simple stimuli. Is it also the case for more complex stimuli? Can they be efficiently processed subliminally and subsequently influence our behavior?

A face can be an example of such an object. Despite the fact that most faces are pretty similar to one another, through the simultaneous analysis of many elements – eyes, lips, nose – our brain is usually able to flawlessly recognize the faces of people we know. Fast and reliable recognition of faces was significant from the perspective of survival, and as such it was promoted over the course of evolution. It is for this reason that the brain houses special regions dedicated exclusively to recognizing faces.

Are the brain mechanisms of face recognition so effective, that they can work, even without the participation of consciousness? Is our brain able to recognize the identity of a given face, even when we are not aware of having seen any face at all? Prof. Anna Nowicka, from Laboratory of Language Neurobiology, and dr. Michał Bola, from Laboratory of Brain Imaging, with their collaborators: Michał Wójcik and Maria Nowicka, attempted to answer this question in a study published recently in the prestigious journal Psychological Science (M. Wójcik, M. Nowicka, M. Bola, A. Nowicka. (2019). Unconscious detection of one’s own image. Psychological Science, 30(4): 471-480. https://doi.org/ 10.1177/0956797618822971). The project was funded by the National Science Centre.

“Results of my previous studies clearly indicated that our own face is to each of us a very strong and important stimulus and as a consequence effectively attracts our attention. This is why we decided to use pictures of our participants’ faces and matched pictures of other people’s faces in our study. We posed the hypothesis that our brain will recognize and react to our own face even when we are unaware that we saw it” – explains Prof. Anna Nowicka, who specializes in studying the mechanics of how we process information about ourselves.

During the experiment participants looked at a cross displayed in the center of a monitor. Simultaneously, pairs of face pictures were shown on each side; on one side was the participant’s own face, and on the other the face of an unknown person. The participants were to ignore the appearing faces and not focus their attention on them. The most important thing in the whole study was that on half of the presentations the faces were clearly visible and easy to recognize, but in the second half they were not visible to the participants.

In what way can a picture of a face be displayed, but simultaneously remain non-visible? The faces were displayed for only 32 ms and were immediately followed by the appearance of a “mask”, or a random pattern that served solely to disrupt the recognition of faces. Additional tests confirmed the effectiveness of this procedure – participants were able to identify faces even at such short presentation times, but after adding the “mask” they were no longer able to determine if a given picture was of their own face. “This type of technique allows us to test – in laboratory conditions – the influence of stimuli that reach our senses, but are not strong enough to reach our consciousness” – relates Dr. Michał Bola, who specializes in the study of unconscious processes.

How can we study whether the brain recognizes a given face, if the participants themselves are unable to determine it? This may be achieved by recording (using EEG) the brain activity of individuals while they completed the task. Directing our attention to one side causes an asymmetry in brain activity: higher activity is recorded in a hemisphere contralateral to attended side (e. g. attended the left side –  higher activity in the right hemisphere). By analyzing these asymmetries, one is able to determine if in a given moment the participant’s attention is directed to the face presented on the left, or on the right.

In the published work, the authors showed that when we see our own face, our attention is automatically directed towards it, even when we are instructed not to do so. “This is a confirmation of earlier research conducted by ourselves, and other teams. We once again showed that stimuli belonging to the self, for example our own name or face, are preferentially processed by us” – comments Prof. Anna Nowicka.

The most important result is in the proof that our brains automatically shift attention in the direction of our own face, also when we are not aware that we saw it. Despite the fact that in the masked trials participants did not realize that at a given moment their own face was presented, their brain focused attention on that side of the field of view. This means that the brain must have – without the participation of consciousness – identified both of the presented faces and reacted to the participant’s face. It thus seems that consciousness is not necessary for recognition of faces after all.

What is the role of consciousness in processing the stimuli that reach our senses? Some researchers and philosophers think that consciousness has no special function. To us, this view seems to be very unintuitive, as we think we are aware of the influence of all stimuli from the environment, and make decisions consciously and rationally. It turns out that this is not true, and that the stimuli we do not see,  is also able to successfully direct our attention. “We’ve long known that certain types of simple and distinct visual stimuli attract our attention automatically, without our will or conscious decision. This can be, for example, a red object among many green objects. In our study we showed that much more complex objects – like faces, which consist of many elements and require more detailed analysis to recognize – can unconsciously attract our attention. Our experiment is part of the research trend indicating that the capacities of our “unconscious mind” are much larger than we previously thought” – summarizes Dr. Michał Bola.

One question that remains unanswered, is why our own face is so effective at attracting our attention. Is it because of the fact that a given faces represents our own “I” (i.e. the self), which would indicate that this effect should be specific only to our own face? Or maybe the cause is extreme familiarity, which would indicate that other faces that are known to us should also attract attention without the engagement of consciousness? The next question is whether the discovered mechanism is specific only to faces (due to its prioritized processing in the brain), or whether other complex objects can also be effectively processed by our brain without consciousness? Future, already planned studies, will aim to investigate those issues.