Hill and Barton studied Olympic competitions in physical combat and found that, when controlled for skill level, athletes wearing red were more lQuantifying the exercise enhancement needed to become more healthy-looking and attractive may lead to more ambitiousikely to win than those wearing blue, even though colours are arbitrarily assigned. In virtual simulations, football goalkeepers are less confident in stopping penalty kicks from players wearing red. Tae kwon do referees are more likely to award points to combatants wearing red,Clofentezine even if their performance is identical to an opponent wearing blue. Facial flushing when angry increases redness in both men and women, and red faces are more likely to be perceived as angry and dominant than fearful. If this was true, and assuming all other face features were held constant, the colour change needed to alter perceived health and attractiveness may exceed the threshold for simple colour discrimination. A reliable change in fitness or hormonal status may only be indicated by a substantial change in skin blood perfusion or oxygenation. Determining psychophysical thresholds for redness discrimination and health and attractiveness judgments may help determine the basis of preferences for facial redness. Facial attractiveness is thought to signal underlying health, and several features of face attractiveness have little effect on attractiveness when perceived health is statistically controlled. However, what is perceived as optimally healthy and what is perceived as optimally attractive do not always align in human face stimuli. It is therefore possible that minor fluctuations in facial redness may be enough to alter perceived attractiveness, whereas perception of health can only be altered by much more prominent redness differences. Determining psychophysical thresholds for facial redness in health and attractiveness judgments will reveal the perceptual association between health and attractiveness when assessed based on facial redness. Facial redness is a result of blood oxygenation and skin perfusion, which can be augmented through aerobic training. Determining the redness change thresholds for perceived facial health and attractiveness may allow researchers to quantify the weekly amount of aerobic exercise required to become healthier-looking and more attractive. Previous research finds that demonstrating the improvement in appearance resulting from a healthier lifestyle can motivate healthier living. Quantifying the exercise enhancement needed to become more healthy-looking and attractive may lead to more ambitious and goal-driven exercise regimens. In the current study, we manipulated facial redness to simulate changes in blood oxygenation level. We then determined redness change thresholds needed to alter three perceptual parameters: facial redness, health, and Citioloneattractiveness. The results of this study could help determine the nature of redness preferences, and could be used to quantify the increases in aerobic exercise needed to augment perceived facial health and attractiveness. Though face colour is just one of several cues to health and attractiveness, the current experiment saw manipulations only in facial redness. Thus, any differences in perceived health and attractiveness in this study came from changes in facial redness. If human redness preferences resulted from a sensory bias, a detectable difference in redness between two otherwise-identical faces should alter their perceived attractiveness. The results of this study show that a small but detectable change in redness does not necessarily alter perceived facial health and attractiveness when using the same testing procedures. Our results are consistent with an attraction to redness that reflects innate or learned preferences for reliable colour cues to health and mate choice, for example blood oxygenation levels associated with cardiovascular fitness. Skin redness increases with oestrogen levels in women, which are raised during periods of high fertility.