Kamea has been experiencing a great deal of pain in her lower back. each morning she wakes anticipated back pain. her experience of pain is in part the result of

Her experience of pain is in part the result of her expectations about pain. Sensory experiences are thought to be formed by the interactions between expectations and incoming sensory information, but these interactions are not very well understood. On the other hand, it has been shown that positive expectations can reduce the subjective experience of pain .

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).