From: Peripheral vision and pattern recognition: A review Journal of Vision. 2011;11(5):13. doi:10.1167/11.5.13 Figure Legend: Spatial summation for the detection of a homogeneous spot of light in central and peripheral vision. (a) Schematic illustration of Riccò's and Piper's law of spatial summation. (b) Spatial summation in peripheral view for two observers (monocular, 15° nasal, dark adapted, 12.8 ms). Data by Graham and Bartlett (1939, Table 2). (c) Diameter of receptive and perceptive fields for the human, monkey, and cat. Open squares: Human perceptive fields, mean of temporal and nasal data provided by Oehler (1985, Figure 4). Open circles: Monkey perceptive fields, obtained by using the Westheimer paradigm (Oehler, 1985, Figure 8). Filled circles: Monkey receptive field (De Monasterio & Gouras, 1975, Figure 16, broad-band cells). Crosses and filled triangles: receptive fields of the cat (Fischer & May, 1970, Figure 2). Analyses by Strasburger (2003b), figures modified from Strasburger (2003). Date of download: 10/19/2017 The Association for Research in Vision and Ophthalmology Copyright © 2017. All rights reserved.