Humans are generally anticipatory beings in that the brain is able to predict future patterns of action and their consequences in the environment. Thus, according to the theory, purposeful action is possible. In a study, a research team led by Dr. David Dignath and Prof. Dr. Andrea Kiesel from the Department of Psychology at the University of Freiburg and colleagues from the University of Trier investigated how such predictions look on the neuronal level. “We assumed that there is neuronal activity that reflects expectations and precedes action,” says Kiesel. The researchers used an electroencephalogram (EEG) to record the brain activity of a total of 60 volunteers. “The results show that the expectation of what we change in the environment can be measured in brain activity even before an action begins,” says Dignath. The results thus confirm the scientists’ assumption and support classical theories of action control. They recently presented their results in the scientific publication Journal of Experimental Psychology: General.     

Theories of psychological action control say that people act to make a difference in their environment. They thus deliberately generate certain effects of action - and are thus actively acting and not passively reacting. "When playing the piano, the keys are pressed either to make only one movement, which is determined by the arrangement of the notes on the sheet of music, or to create a melody as an effect," says Kiesel. The aim of this study was to demonstrate that such effects are measurable in the EEG while an action is planned but not yet performed.

During the experiments, the subjects pressed two different computer keys several hundred times. When pressing one of the keys, the image flickered at a frequency of six Hertz. When the other key was pressed, an image appeared that flickered much faster, at a frequency of ten Hertz. By pressing the keys alternately, the participants learned when which picture appeared and developed a corresponding expectation. “The brain reacted particularly strongly to the frequency at which the image was shown, i.e. either six or ten Hertz in this experiment,” explains Dignath. This, in turn, is shown in the EEG, while the subjects observed the flickering images that followed the keystroke.

The researchers were able to prove for the first time that it is possible to read out which image is generated from the EEG signal before the start of the action. For example, brain activity in the EEG showed a characteristic pattern before a key was pressed. “Our brain functions via contrasts,” explains Dignath, meaning that shortly before the subject presses one of the two keys, the brain shows less neuronal activity in a certain area than at rest. “When the image actually appears, the activity in that area increases, so that it is quickly registered. The special thing about it is that this type of anticipation is directly visible in the EEG, even before the actual action is performed,” emphasizes Dignath.

Original publication:
Dignath, D., Kiesel, A., Frings, C., Pastötter, B. (forthcoming): Electrophysiological evidence for action-effect prediction, in: Journal of Experimental Psychology: General. DOI: 10.1037/xge0000707.