title: Sensitivity to spatial and temporal modulations of first-order and second-order motion.
abstract: This study characterises the spatiotemporal "window of visibility" for first-order motion (luminance-modulated noise) and three varieties of second-order motion (contrast-modulated, polarity-modulated and spatial length-modulated noise). Direction-identification thresholds (minimum modulation depth producing 79.4% correct) were measured for each motion pattern (acuity permitting) over a five octave range of spatial and temporal frequencies (0.5-16 c/deg and 0.5-16 Hz respectively). Thresholds were converted into modulation sensitivity (1/threshold). For first-order motion patterns, sensitivity functions were generally bandpass. However, for second-order motion patterns, functions were predominantly lowpass in nature. In particular, the functions corresponding to contrast-modulated and polarity-modulated noise were virtually identical in terms of shape and sensitivity. However, sensitivity to modulations of spatial length was extremely poor and more lowpass, suggesting that additional strategies, perhaps a feature-based system, may be required for encoding motion of images of this type.
authors.affiliation: School of Psychology, University of Nottingham, University Park, Nottingham NG7 2RD, UK. lpxcvh@psychology.nottingham.ac.uk
authors.forename: Claire V
authors.initials: CV
authors.lastname: Hutchinson
authors.forename: Timothy
authors.initials: T
authors.lastname: Ledgeway
mesh_terms: D015350:Contrast Sensitivity / Q000502:physiology; D006801:Humans; D008029:Lighting; D009038:Motion; D009039:Motion Perception / Q000502:physiology*; D009949:Orientation; D010364:Pattern Recognition, Visual / Q000502:physiology; D010470:Perceptual Masking; D011601:Psychophysics; D012684:Sensory Thresholds