sweetness preference refers to the predilection for sweet tastes observed in numerous species, including humans, from infancy on. Our sense of taste is unlike any of our other senses, in that we are born with established likes and dislikes for its fundamental qualities. This fact reveals that there is something quite crucial about taste that cannot wait for the normal processes of postnatal experience and learning. From an evolutionary standpoint, sensitivities to sweetness (as a signal for calories), bitterness (toxins), and saltiness (sodium) are likely to have important roles in regulating the intake of nutrients and avoidance of toxins. This interpretation is supported by findings in rats of strong inverse associations between degree of toxicity of taste compounds and their palatability.