Measuring spatial perception with spatial updating and action
Measurement of perceived egocentric distance, whether of visual or auditory targets, is a topic of fundamental importance that is still being actively pursued and debated. Beyond its intrinsic interest to psychologists and philosophers alike, it is important to the understanding of many other topics which involve distance perception. For example, many complex behaviors like driving, piloting of aircraft, sport activities, and dance often involve distance perception. Consequently, understanding when and why errors in distance perception occur will illuminate the reasons for error and disfluency in these behaviors. Also, the understanding of distance perception is important in the current debate about the "two visual systems," one ostensibly concerned with the conscious perception of 3-D space and the other with on-line control of action. Similarly, determining whether nonsensory factors, such as intention to act and energetic state of the observer, influence perceived distance, as has been claimed (e.g. Proffitt, Stefanucci, Banton, & Epstein, 2003; Witt, Proffitt, & Epstein, 2004, 2005) depends critically on the meaning of distance perception and how it is to be measured. Still another topic where measurement of distance perception is critical is spatial updating (the imaginal updating of a target perceived only prior to observer movement) involving observer translation. Being able to measure the accuracy of spatial updating depends upon being able to partial out errors due to misperception ofthe initial target distance (Book & Garling, 1981; Loomis, Klatzky, Philbeck, & Golledge, 1998; Loomis, Lippa, Klatzky & Golledge, 2002; Philbeck, Loomis, & Beall, 1997). Finally, measurement of distance perception is important for the development of effective visual and auditory displays of 3-D space. Indeed, developing virtual reality systems that exhibit naturally appearing scale has proven an enormous challenge, both for visual virtual reality (Loomis & Knapp, 2003) and for auditory virtual reality (Loomis, Klatzky, & Golledge, 1999), and there has been a spate of recent research articles concerned with understanding the causes for uniform scale compression in many visual virtual environments (e.g., Creem-Regehr, Willemsen, Gooch, & Thompson, 2005; Knapp, 1999; Knapp & Loomis, 2004; Sahm, Creem-Regehr, Thompson, & Willemsen, 2005; Thompson, Willemsen, Gooch, Creem-Regehr, Loomis et al., 2004). Virtual reality systems that successfully create a realistic sense of scale will enjoy even greater aesthetic impact and user acceptance and will prove even more useful in the training of skills, such as safe road crossing behavior by blind and sighted children.