  Social media filters combined with recommender systems can lead to the
emergence of filter bubbles and polarized groups. In addition, segregation
processes of human groups in certain social contexts have been shown to share
some similarities with phase separation phenomena in physics. Here, we study
the impact of information filtering on collective segregation behavior. We
report a series of experiments where groups of 22 subjects have to perform a
collective segregation task that mimics the tendency of individuals to bond
with other similar individuals. More precisely, the participants are each
assigned a color (red or blue) unknown to them, and have to regroup with other
subjects sharing the same color. To assist them, they are equipped with an
artificial sensory device capable of detecting the majority color in their
``environment'' (defined as their $k$ nearest neighbors, unbeknownst to them),
for which we control the perception range, $k=1,3,5,7,9,11,13$. We study the
separation dynamics (emergence of unicolor groups) and the properties of the
final state, and show that the value of $k$ controls the quality of the
segregation, although the subjects are totally unaware of the precise
definition of the ``environment''. We also find that there is a perception
range $k=7$ above which the ability of the group to segregate does not improve.
We introduce a model that precisely describes the random motion of a group of
pedestrians in a confined space, and which faithfully reproduces and allows to
interpret the results of the segregation experiments. Finally, we discuss the
strong and precise analogy between our experiment and the phase separation of
two immiscible materials at very low temperature.
