According to research, the average age of menarche for girls in the United States is

Which of the following events most intrigued Pavlov and led to his discoveries?

a) The dogs seemed to enjoy the food. b) The assistant salivated along with the dogs when the dogs started to eat. c) The dogs stopped salivating after seeing the assistant so many times. d) The dogs started to salivate when they saw Pavlov's assistant and before they got the food.

According to Vygotsky, cognitive development proceeds as a result of

A) proceeding through qualitative stages of development. B) social interactions in which partners jointly work together to solve problems. C) maturation of the prefrontal cortex of the brain. D) increased speed of information processing.