IMAGE 2013 Conference ______________________________ Presented at the IMAGE 2013 Conference Scottsdale, Arizona – June 2013 VECTION: WHAT IS IT AND CAN A SIMULATOR VISUAL SYSTEM INDUCE THE PHENOMENON? Frank M. Cardullo & Kirill Zaychik Man-Machine Systems Laboratory, Dept. of Mechanical Engineering State University of New York at Binghamton NY, USA ABSTRACT Visually induced self-motion, often referred to as vection, is a phenomenon that is often observed in the real world. The famous railroad station paradox is an often quoted example. In this manifestation a person in a stationary train experiences the illusion that he/she is moving when the adjacent train begins to move. Once the person realizes that he/she has not received vestibular or somatosensory stimulation or gazes at a fixed object the illusion is destroyed and replaced with a veridical sense of homeostasis. Past research has indicated that there is latency in the onset of the vection illusion from about a second to as long as 10 seconds. Furthermore it has been found that this latency can be reduced to as little as 0.1 second if a vestibular stimulus of even a jolt in the appropriate direction. However it also has been shown that a superliminal vestibular stimulus in the wrong direction will abruptly destroy well developed vection. Until recently virtually all this research has been conducted in a laboratory and not in a flight simulator. This paper will reviews the recent literature to assess the extent to which the above questions have been answered. It will also discuss the development of a novel approach to quantitative metrics for assessing the ability of simulator visual systems to induce vection. Finally it presents a protocol and instrumentation for experiments to measure the occurrence of vection in a driving simulator BACKGROUND This section provides the reader with a general background on the visually induced perception of ego motion also known as vection. However, before proceeding with a description of vection it is important to introduce such terminology as egocentric and exocentric types of perception of motion. An egocentric reference frame is defined with respect to the observer. Whereas the reference frame associated with something external to the body of the observer is referred to as an exocentric frame. Following the same logic one can speculate that optokinetic stimuli can evoke two types of perceptual interpretations: the observer may perceive him/her- self as being stationary in a moving surround (egocentric motion perception) or he/she may experience an illusion of self-motion where the surroundings appear to be moving while, in fact, they remain stationary (exocentric motion perception). Young 1 references work by Ernst Mach 2 , who was the first to experiment with the rotating drum with alternating visual patterns to provoke the illusion of self motion. In 1895, Wood 3 published his work on investigating of illusion of self motion in an amusement park ride called “The Haunted Swing” (Figure 1). The image in the picture illustrates what people must have been experiencing during ride’s function. Vection, a term conventionally accepted by the research community, was first introduced by Tschermark 4 , refers to an illusion of self-motion induced by optical flow patterns, which resemble a form of self motion experience. Dichgans and Brandt 5 anchored the term vection by associating it with the visually induced illusion of absolute self- motion without actual displacement in space. The following are a few examples of common-life situations where vection onset is highly probable. 1. Railroad station paradox: An observer looks outside the window and sees another stationary train. As that train starts to move the observer experiences