The Heights of Illusion

Evolved navigation theory and the environmental vertical illusion

“…), or a 4.2 % vertical overestimation. The current mean estimate is also highly similar to those of previous VHI research that used similar methods, which found vertical overestimations from 2.9 to 7.1% (Avery & Day, 1969;Bolton, Michelson, Wilde, & Bolton, 1975;Künnapas, 1957a;Künnapas, 1957b;Künnapas, 1958;Raudsepp, 2002). …”

“…This result is highly similar to the identical VHI task in Study 1 that featured an average VHI of 4.2%. The current mean estimate is also highly similar to those of previous VHI research that used similar methods, which found vertical overestimations from 2.9 to 7.1% (Avery & Day, 1969;Bolton, Michelson, Wilde, & Bolton, 1975;Künnapas, 1957a;Künnapas, 1957b;Künnapas, 1958;Raudsepp, 2002 No experiential question correlated with VHI estimates (the most significant of which r (102) = -.131, p = .185). Whether or not a participant had previously fallen to injury failed to relate significantly to any distance estimate (the most significant of which t (103) = 1.588, p = .115).…”

“…Contrary to this theory, overestimation of retinally vertical extents reliably develops in all human populations yet studied, including those with minimal receding horizontals, such as the Todas of southern India and Papuans of New Guinea at the turn of the 20 th century (Rivers, 1905), as well as jungle-dwelling Peruvians (Bolton, Michelson, Wilde, & Bolton, 1975). Vertical overestimation even occurs in non-humans (chicks, see Winslow, 1933), including non-humans with extensively vertical environments (monkeys, see Dominguez, 1954).…”

Evolved navigation theory and the descent illusion

“…ENT also suggests cross-cultural VHI prevalence, because vertical surfaces pose falling costs to all humans. Consistent with ENT, all human populations yet studied display the VHI; this includes populations in environments with minimal receding horizontals, such as the Todas of southern India and the Papuans of New Guinea at the turn of the 20th century (Rivers, 1905), as well as jungle-dwelling Peruvians (Bolton, Michelson, Wilde, & Bolton, 1975). ENT predicts VHI existence across humans as a species, but ENT also predicts VHI differences within and between human populations, resulting from variable falling experience and exposure to fall-inducing environments.…”

Measurement of developmental susceptibility to the horizontal‐vertical illusion

“…Fig. 1) is of the order of 3-5 per cent in adults (Kunnapas, 1955;Avery & Day, 1969), although reports have been made that the extent of the illusion varies with the cultural background of the subjects tested (Rivers, 1905;Segall et al, 1963;Jahoda, 1966;Deregowski, 1967;Bolton et al, 1975).…”