  The existing computational models used to estimate motion sickness are
incapable of describing the fact that the predictability of motion patterns
affects motion sickness. Therefore, the present study proposes a computational
model to describe the effect of the predictability of dynamics or the pattern
of motion stimuli on motion sickness. In the proposed model, a submodel, in
which a recursive Gaussian process regression is used to represent human
features of online learning and future prediction of motion dynamics, is
combined with a conventional model of motion sickness based on an observer
theory. A simulation experiment was conducted in which the proposed model
predicted motion sickness caused by a 900 s horizontal movement. The movement
was composed of a 9 m repetitive back-and-forth movement pattern with a pause.
Regarding the motion condition, the direction and timing of the motion were
varied as follows: a) Predictable motion (M_P): the direction of the motion and
duration of the pause were set to 8 s; b) Motion with unpredicted direction
(M_dU): the pause duration was fixed as in (P), but the motion direction was
randomly determined; c) Motion with unpredicted timing (M_tU): the motion
direction was fixed as in (M_P), but the pause duration was randomly selected
from 4 to 12 s. The results obtained using the proposed model demonstrated that
the predicted motion sickness incidence for (M_P) was smaller than those for
(M_dU) and (M_tU). This tendency agrees with the sickness patterns observed in
a previous experimental study in which the human participants were subject to
motion conditions similar to those used in our simulations. Moreover, no
significant differences were found in the predicted motion sickness incidences
at different conditions when the conventional model was used.
