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Nobu Shirai, Tomoko Imura, Yuko Hattori, Masaki Tomonaga, Masami K. Yamaguchi; Perception of radial motion in Japanese macaque (Macaca fuscata) infants. Journal of Vision 2007;7(9):750. doi: 10.1167/7.9.750.
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© ARVO (1962-2015); The Authors (2016-present)
Radial motion is an important cue to perceive motion-in-depth, such as the observer's own forward/backward locomotion or an approaching/receding object to/from the observer. Early development of radial motion sensitivity in human infants has been described by several psychophysical researches (e.g., Gilmore & Rettke, 2003; Gilmore et al., 2004; Shirai et al., 2004a, 2004b, 2006). On the other hand, there are few data regarding development of radial motion sensitivity in non-human primates (but see Schiff et al., 1962). Here we report early development of radial expansion/contraction sensitivity in Japanese macaque monkeys. Fifteen 1- to 5-month-old infant monkeys (mean age=90.3days, SD=43.0) participated in the present study. We examined the infants' preference for radial motion using almost same experimental methods as those of Shirai et al. (2005). Our stimulus was composed of two dynamic random dot patterns (RDPs) placed side by side. One RDP was a radial expansion (or contraction) and the other was translation (up, down, right, or left-ward: counter balanced across infants). Each RDP consisted of 100 moving dots, which moved at constant speed (10.62/deg). Hence each RDP has no speed gradient. There were two experimental conditions (“expansion vs. translation” and “contraction vs. translation”), and each infant participated in both conditions. Each experimental condition consisted of 12 trials. In each trial, a stimulus was presented to the infants for 3 s. One observer, who was naïve for the stimulus identity, made 2AFC judgment about the infant's first gaze direction (left or right) in each trial (FPL method). The current results indicate that the infants showed significant preference for expansion to translations, but did not show significant preference for contraction. We will discuss about the early development of radial motion sensitivity in primates, based on the results of present monkey study and those of previous human infant studies.
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