Final answer:
The statement that evidence of disgust has not been observed in infants younger than two months is not true. Infants demonstrate behaviors related to aversion, including reactions to bitterness, which can be considered early forms of disgust.
Step-by-step explanation:
The question asks which statement about disgust is not true. Evaluating the options given:
a) Infants have an innate aversion to bitterness.
b) Evidence of disgust has not been observed in infants younger than two months.
c) Children typically struggle to identify disgust before age 4 or 5.
d) Disgust is believed to have evolved to help humans avoid things that will make them sick.
Research has shown that infants do have an innate aversion to bitterness, which is likely a protective mechanism to avoid potentially toxic substances. While the senses of taste and smell develop and change over time, an infant's reaction to bitter tastes is observable early on. Additionally, although children's full understanding of the range of facial expressions related to disgust may not develop until around age 4 or 5, the basic aversion behavior is present earlier. Lastly, disgust is indeed thought to have evolved as a means to help humans avoid substances or situations that could cause illness.
Given this information, the statement b) is not true as some evidence is found in infants demonstrating behaviors associated with aversion or disgust even before two months of age.