Biomedical Engineering Reference
In-Depth Information
quency (“going down”) facilitated downwards vertical vection, but had no effect on
any other vection direction. Similar effects of spatial metaphor mapping have been
observed for the emotional connotation of sounds, in that emotionally “positive”
sounds facilitated upwards vection compared to neural sounds [
99
]. Together, these
findings further corroborate the proposition that multi-modal consistency between
different stimuli can facilitate vection [
86
,
94
,
96
,
102
], even in situations where
this correspondence is only metaphorical and not purely sensorial. However, as vec-
tion is an inherently subjective phenomenon, vection researchers need to carefully
assess potential experimental biases such as perceived demand characteristics of the
experimental situation and participants' expectations and prior knowledge.
Cognitive-perceptual framework of movability.
A number of studies demonstrated
that merely knowing/perceiving that actual motion is impossible versus possible can
reduce visual vection, both in the real world and VR [
3
,
57
,
130
]. For example,
Andersen and Braunstein [
3
] remark that pilot experiments had shown that in order
to perceive any self-motion, participants had to believe that they could actually be
moved in the direction of perceived vection. Accordingly, participants were asked to
stand in a movable booth and looked out of a window to view the optic flow pattern.
This procedure allowed them to elicit vection with a visual FOV as small as 7
5
◦
.
Lepecq et al. [
57
] demonstrated that seven year old children perceive vection earlier
when they were previously shown that the chair they were seated on could physically
move in the direction of simulated motion—even though this never happened dur-
ing the actual experiment. Similarly, knowing that actual motion is possible in VR
(by demonstrating the motion capabilities of a motion platform prior to testing) can
make people believe that they actually moved, even though they never did [
86
,
100
].
Recently, Riecke et al. [
85
] demonstrated that providing such a cognitive-perceptual
framework of movability can also enhance auditory vection. When blindfolded par-
ticipants were seated on a hammock chair while listening to binaural recordings of
rotating sound fields, auditory circular vection was facilitated when participants'
feet were suspended by a chair-attached footrest as compared to being positioned on
solid ground. This supports the common practice of seating participants on poten-
tially moveable platforms or chairs in order to elicit auditory vection [
54
,
117
,
118
].
.
Attention and cognitive load.
There seems to be mixed evidence about the poten-
tial effects of attention and cognitive load on vection. Whereas Trutoiu et al. [
113
]
observed vection facilitation when participants had to perform a cognitively demand-
ing secondary task, vection inhibition was reported by Seno and colleagues [
105
].
When observers in [
53
] were asked to specifically attend one of two simultane-
ously presented upward and downward optic flow fields of different colors, the
non-attended flow field was found to determine vection direction. This might, how-
ever, also be explained by attention modulating the perceived depth-ordering and
foreground-background relationship, as discussed in detail in [
75
,
103
] demonstrated
that cognitive priming can also affect the time course of vection: Adult participants
experienced vection earlier when they were seated on a potentially movable chair
and were primed towards paying attention to self-motion sensation, compared to a
condition where they were seated on a stationary chair and instructed to attend to
