Biomedical Engineering Reference
In-Depth Information
[
23
,
81
,
82
]. For example, auditory vection was enhanced when the moving sounds
represented “acoustic landmarks”, i.e., objects that do not normally move such as
church bells, as compared to typically moving objects like cars or artificial sounds like
pink noise [
56
,
96
,
118
].
For visual vection Riecke et al. [
84
] demonstrated that vection as well as presence
were impaired when the naturalistic stimulus of a city environment was system-
atically degraded by mosaic-like scrambling. Different aspects of presence were
correlated with specific aspects of vection: Whereas spatial presence correlated most
strongly with the convincingness of illusory self-motion, attention/involvement in the
simulation correlated predominately with vection onset latency. In a second experi-
ment, the visual stimulus of a natural scene was compared to an upside-down version
of the same stimulus. Even though the inversion of the stimulus left the physical stim-
ulus characteristics (i.e., the image statistics and thus perceptual/bottom-up factors)
essentially unaltered, both presence and the convincingness of vection were sig-
nificantly reduced. This strongly suggests a cognitive or top-down contribution to
presence and the convincingness of self-motion illusions. We posit that the natural,
ecologically more plausible upright stimulus might have more easily been accepted
as a stable “scene”, which in turn facilitated both presence and the convincingness
of vection.
These findings are supported by tumbling room studies, where the tumbling sen-
sation (roll vection) is enhanced for naturalistic environments that include a clear
visual frame of reference and objects with an obvious intrinsic upright orientation
[
1
,
40
]. That is, whereas simple textured displays only tend to produce limited tilting
sensations [
1
,
32
,
133
], observing a fully furnished natural room rotating around
stationary participants can induce compelling 360
◦
head-over-heals tumbling sensa-
tion in most people [
1
,
40
,
43
,
71
]. Moreover, Palmisano et al. stated that “the 360
◦
illusory self-rotations produced by rotating a furnished room around the stationary
observer's roll axis were very similar to the sensations of self-rotation produced by
rotating the observer inside the stationary room” (p. 4057). The importance of a
naturalistic visual stimulus is corroborated by Wright et al. who demonstrated that
visual motion of a photo-realistic visual scene can dominate even conflicting inertial
motion cues in the perception of self-motion [
128
,
129
].
Metaphorical cross-modal facilitation of vection.
Recently, Seno et al. demon-
strated that linear visual vection could even be facilitated by auditory cues that do not
move by themselves, but only match the visual motion metaphor [
102
]. For example,
sounds increasing in amplitude (as if coming closer) facilitated visually-induced for-
ward vection, but not backwards, sideways (left-right) or vertical (up-down) vection.
Sounds decreasing in amplitude did not show any clear effects on vection, though.
Whereas forward motions in normal life are often accompanied by increasing sound
amplitudes for sounding stationary objects in front of us, this physical correspon-
dence to real-world situations does not seem to be necessary for sound to facilitate
visually-induced vection: Sounds ascending (“going up”) in frequency facilitated
upwards vertical vection, but had no influence on downwards, sideways (left-right),
or forward-backwards vection [
102
]. Correspondingly, sounds decreasing in fre-
