Understanding the Signals of Pain

By Jane Farrell

Researchers have drawn closer to an understanding of higher cognitive processes by discovering that people learn pain cues even though they are unaware of such cues.

Investigators from the Karolinska Institute, in Stockholm, looked at 49 people who were assigned into four groups that would examine the levels of conscious awareness during the experiment.

According to a release from the institute, images of different faces were presented on a computer screen. To some of the participants the images were shown so quickly that they could not be consciously recognized. For each image exposure, participants were subjected to pain stimulation and asked to rate the pain according to a specific scale. As each image was repeatedly associated with either high or low pain, it turned into a high pain cue or a low pain cue that would affect the participants’ expectations.

The results suggest that pain cues could be learned without conscious awareness, as participants reported increased pain when shown the high pain image and reduced pain when shown the low pain image during identical levels of pain stimulation, regardless of whether or not the images were shown subliminally,

“These results demonstrate that pain responses can be shaped by learning that takes place outside conscious awareness, suggesting that unconscious learning may have an extensive effect on higher cognitive processes in general”, said Dr. Karin Jensen, a researcher in the department of Clinical Neuroscience.

The findings were published in the journal PNAS.