Billock, Cunningham & Tsou (2008) 4 APPROVED FOR PUBLIC RELEASEand recognition times following detection increase by an additional 20% (O'Neill et al., 2004). Some newer camouflage schemes-inspired by fractals-have more than two scales. (True fractal camouflage would be defined by statistical similarity at every visible spatial scale, but limited size and printing resolution result in a restricted range of scales. ) More complicated schemes are possible, including the use of multi-fractals which mimic blends of particular textures that occur in natural images (e. g., plant growth on fractured rock). Here, we study human abilities to discriminate images based on small differences in the ȕ signature and place the results in context with camouflage and with earlier texture discrimination studies. Figure 2. Fractal textures like those used in the experiments. Each fractal in this figure has 1/fβ amplitude spectrum and identical phase spectra, and is synthesized by spatial frequency filtering the same set of random gray levels. The lack of weight in the higher spatial frequencies can easily be seen in the coarseness of the images as the exponent β increases.