Biomedical Engineering Reference
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object motion, not self-motion. Thus, while attention and cognitive load can clearly
affect self-motion illusions, further research is needed to elucidate underlying factors
and explain seemingly conflicting findings. A recent study suggests that vection can
even be induced when participants are not consciously aware of any global display
motion, which was cleverly masked by strong local moving contrasts [ 107 ].
Finally, the occurrence, onset latency, and perceived strength of vection tend to vary
considerably between participants. Although there is little research investigating
potential underlying factors, recent research suggests that personality traits might
be a contributing factor. In a linear visual vection study, more narcissistic observers
reported weaker vection, indicated by increased vection onset latencies, reduced
vection duration, and decreased vection magnitude [ 108 ]. Future research is needed
to investigate if differences in personality traits indeed directly affect the self-motion
illusions, and/or if the observed vection reduction for increasing narcissism might
also be related to a criterion shift for reporting vection.
In general, cognitive factors seem to become more relevant when stimuli are ambigu-
ous or have only weak vection-inducing power, as in the case of auditory vection
[ 85 ] or sparse or small-FOV visual stimuli [ 3 ]. It is conceivable that cognitive fac-
tors generally have an effect on vection, but that this has not been widely recognized
for methodological reasons. For example, the cognitive manipulations might not
have been powerful enough or free of confounds, or sensory stimulation might have
been so strong that ceiling level was already reached, which is likely the case in an
optokinetic drum that covers the full visible FOV.
2.8 Does Vection Improve Spatial Updating and Perspective
Switches?
Spatial updating is seemingly automatic and requires little cognitive resources if
participants physically move to the new position [ 80 , 97 ]. For example, humans can
continuously and accurately point to a previously-seen target when either walking
or being passively transported, both for linear motions [ 20 , 109 ] and curvilinear
motions [ 29 ]. However, when participants in Frissen et al. [ 29 ] were stationary and
only biomechanical cues from stepping along a circular treadmill indicated the curvi-
linear motion, spatial updating performance (quantified using continuous pointing)
declined and showed systematic errors. The authors did not assess whether partic-
ipants in some trials might have perceived biomechanical vection. In a follow-up
study by Frissen et al. continuous pointing responses indicated that participants can
indeed perceive a slow drift (about 7 /s) for curvilinear off-center walking-in-place
on a large (3.6 m diameter) circular treadmill, but only at about 16 % of their actual
walking speed of 40 /s (cf. Chap. 6 of this topic). Surprisingly, although participants
were always walking forward , pointing responses indicated backward self-motion in
42 % of the trials. This suggests that biomechanical cues from curvilinear forward
walking were not sufficient for inducing a reliable sensation of forward self-motion.
 
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