Fig. 1. Spontaneous emergence of face-selectivity in untrained networks.

a Face-selective neurons and their response observed in monkey experiments. The response was normalized to the maximum value as 1. The face image shown is not the original stimulus set due to copyright. The image shown is available at [https://www.shutterstock.com] (see Methods for details). b The architecture of the untrained AlexNet⁴⁵. The untrained AlexNet was devised using a random initialization method⁵⁸, for which the values in each weight kernel were randomly sampled from a Gaussian distribution. c A stimulus set was designed to control the degree of intra-class image similarity. Stimulus images were selected and modified from a publicly available dataset that has been used in human fMRI study⁵⁹. The original images are available at [http://vpnl.stanford.edu/fLoc/]. d Responses of individual face-selective units in the untrained AlexNet (P < 0.001, two-sided rank-sum test, uncorrected). e The number of face-selective units in each convolutional layer in untrained networks (n = 100). f Face-selectivity index (FSI) of face-selective neurons in the primate IT⁷ (n = 158), and face units in each convolutional layer in the untrained AlexNet. The control FSI was measured according to the shuffled responses of face-selective units in the untrained network. g (Left) Examples of texform and scrambled face images. (Right) Responses of face-selective units to the original face (n = 200), the scrambled face (n = 200) and texform face images (n = 100). h Responses of face-selective units to four different sets of novel face images: (1) 50 face images from our original dataset (images not used for finding face-selective units), (2) 16 images used in Tsao et al.^5,7, (3) 50 images used in Cao et al.⁶² in color and gray scale, and (4) 50 face images artificially generated by the FaceGen simulator (singular inversions) in color and gray scale. i The number of face-selective units, where the weight variation was changed from 5 to 200% of the original value using two different initialization methods with a Gaussian (red) and a uniform distribution (blue). j FSI of face-selective units across changes in the weight. Dashed lines indicate the mean and shaded areas indicate the standard deviation of 30 random networks. All box plots indicate the inter-quartile range (IQR between Q1 and Q3) of the dataset, the horizontal line depicts the median and the whiskers correspond to the rest of the distribution (Q1 − 1.5*IQR, Q3 + 1.5*IQR).