Psychologists at the University of Osnabrück have shown that in conditions of sensory uncertainty, a person tends to make decisions based on assumptions, rather than reliable information.
An important condition for adaptive behavior is the integration of sensory stimuli. In some cases, for example, in trauma, this process can be disrupted, which leads to the need to make up for the lack of incoming information based on past experience. However, direct perception of the environment is limited even in the norm. In chordates, an example of this is the blind spot - the place of entry into the retina of the optic nerve, where there are no photoreceptors. In a blind spot (at one of the points on the periphery of vision), the visible object “disappears” and is recreated by the brain based on hypotheses. How the reliability of the recreated elements of the perceptual picture is assessed has not been sufficiently studied.
To find out, the authors of the new work conducted a series of experiments. Volunteers performed a two-way forced choice task (2AFC task). At the first stage, 24 of them in pairs showed a circle with a continuous black-and-white pattern and the same circle, but with an artifact in the center, on a 3D monitor. When the first was placed in the area of the blind spot (on the periphery), its center was invisible, while both stimuli, due to shutter glasses, were perceived by the participants with only one eye. They then indicated which of the circles does not contain or contains the artifact. In total, 100 people took part in the work, in four other sessions additional conditions were used.
Incentive material and an example of an experimental session. The area of the blind spot on the retina and the corresponding "observed" area are indicated in blue / Benedikt V Ehinger et al., ELife, 2017
Thanks to this design, scientists could assess the specifics of decision-making in a situation of uncertainty. According to the main hypothesis, due to the incompleteness of the picture, the participants could not reliably distinguish the circles, so their choice should be random (despite the seeming simplicity of the task, it is worth considering that perception in this case was distorted by monocular vision: the missing links were also "completed" with a closed eye who could "mix" the images visible to the other eye, leveling the differences between them). An alternative assumption was that subjects trusted more stimuli outside the blind spot and, as a result, would be more likely to choose them.
However, the results showed the opposite: the volunteers preferred stimuli that were in the blind spot area. The trend persisted even when the scientists adjusted for the possible tendency to choose circles located in a particular area (in the last experiment, stimuli with an artifact were always in the focal plane). The reason for this behavior is unclear. According to the authors, the data obtained indicate that in the case of a person, the alleged information, apparently, exceeds the reliable (visible) information on the criterion of value. This may be due to increased activity of neurons in the optic nerve area or a coding error.
The article was published in the eLife magazine.
Denis Strigun
Promotional video: