Obstacle perception by ongenitally blind children

Abstract

The ability to perceive objects from a distance and navigate without vision depends principally on auditory information. Two experiments were conducted in order to assess this ability in congenitally blind children aged 4 to 12 years who had negligible amounts of visual experience or formal mobility training. In Experiment 1, children walked along a sidewalk toward a target location to get some candy. A box was placed along the path on some trials, and the children were instructed to avoid the box if it was present. The children spent more time in the region just in front of the box than in the region just behind it, indicating that they perceived the box and acted 80 as to navigate around it. In Experiment 2, children attempted to discriminate whether a nearby disk was on their left or on their right. The children performed at above-chance levels, again indicating distal perception of objects. fie results of both experiments suggest that blind children with little or no visual experience or formal training utilize-nonvisual information, presumably auditory, to perceive objects. The specific nature of this auditory information requires further investigation, but these findings imply that the underlying perceptual ability does not require experience in spatial vision or deliberate training and intervention.Navigation through cluttered environments depends on perception of the locations of objects and surfaces so that obstacles can be avoided and clear pathways can be used. Although vision is ideally suited for this task, both blind observers and blindfolded sighted observers can locomote without collisions through spaces containing large objects (Supa, Cotzin, & Dallenbach, 1944; Worchel, Mauny, & Andrew, 1950). Various explanatory processes for this ability to navigate without vision have been proposed over the years, including "facial vision" resulting from sensitivity to changes in air pressure near surfaces, a "sixth sense" unique to blind persons, and echolocation based on reflected sounds. The ability is mediated by sensitivity to auditory information, probably in the form of reflected sounds or sound shadows. For example, Supa et al. (1944) found that both blind observers and blindfolded sighted observers who could otherwise stop I-2m in front of a large panel collided with it if their hearing was strongly attenuated. Attenuation of other potential sensory information, such as tactile or thermal stimulation, did not adversely affect performance, so it was concluded that auditory information was necessary and sufficient.

Virtual environments for the transfer of navigation skills in the blind: a comparison of directed instruction vs. video game based learning approaches

“…Given that visual cues play a crucial role in capturing and organizing spatial formation, it has been assumed that blind individuals (and in particular, those who are born with profound blindness) would be impaired in creating an accurate mental spatial representation of their surroundings (von Senden, 1960; Ashmead et al, 1989; Thinus-Blanc and Gaunet, 1997; see also Blasch et al, 1997 for further discussion). It is thus of interest that both early and late blind participants showed similar levels of performance in this study.…”

“…Blind individuals typically undergo formal instruction referred to as orientation and mobility (O&M) training as a means of learning how to navigate independently through the environment. Unlike the sighted, blind individuals must rely on other sensory channels (such as hearing, touch, and proprioception Thinus-Blanc and Gaunet, 1997) to gather relevant spatial information for orientating, route planning, and path execution (Strelow, 1985; Ashmead et al, 1989; Loomis et al, 1993; Long and Giudice, 2010). The resultant mental representation of the surrounding space is referred to as a spatial cognitive map (Strelow, 1985), and generating an accurate and robust mental map is considered essential for efficient travel (Siegel and White, 1975; Blasch et al, 1997).…”

“…Further, these cognitive gains (i.e., near transfer of learning) would only arise if exploration occurred within an environment that corresponded to the target building where the acquired skills would ultimately be assessed. Secondly, given previous accounts suggesting that prior visual experience may have a beneficial effect on the ability to mentally represent surrounding space (Ashmead et al, 1989), we hypothesized that late blind participants (i.e., individuals having greater prior visual experience) would show a behavioral advantage compared to their early blind counterparts.…”

Correlation between vividness of visual imagery and echolocation ability in sighted, echo-naïve people

“…There is evidence that blind people are better at echolocation than those who are sighted (see Teng and Whitney 2011, for a summary) and one possible reason for this might be that blind people are generally more sensitive to acoustic reverberations (Dufour et al 2005;Kolarik et al 2013). There are also substantial differences in echolocation capacities between blind people, with congenital blind children often needing no training (Ashmead et al 1989), and people who lose vision earlier in life showing better performance (Teng et al 2012). In sighted people Teng and Whitney (2011) found that all of their sighted novices improved their echolocation ability with regard to size discrimination across multiple sessions, but also that there was variability across participants.…”

Lateralization of two-transient stimuli

“…Such findings are usually associated with the precedence effect in sound localization (Wallach, Newman, & Rosenzweig, 1949;see Zurek, 1987, for a review). The precedence effect has been the topic of extensive physiological (Cranford & Oberholtzer, 1976;Yin & Litovsky, 1995), developmental (Clifton, Morrongiello, & Dowd, 1984;Morrongiello, Clifton, & Kulig, 1982), applied (Blauert, 1989;Muncey, Nickson, & Dubout, 1953;Snow, 1954), and clinical (Ashmead, Hill, & Taylor, 1989;Ashmead et al, 1998;Hochster & Kelly, 1981) study within the hearing sciences.…”