 One suggestion for a supplemented-competition mechanism for attentional selectivity is the biased-competition model, elaborated in several works by Robert Desimone, John Duncan and John Reynolds. The biased-competition model accounts for various attention-involving effects, at the personal and at the sub-personal level, as being effects that arise from numerous struggles between the different stimuli that fall within the variously sized receptive fields of neurons throughout the perceptual processing hierarchy. It is hypothesized that each one of these struggles is biased, although not settled outright, by a top-down attention-specific signal (Desimone and Duncan, 1995, Reynolds and Desimone, 2001).