Ken is planning on studying the influence of intelligence on the ability to recall events from the 1960s. If Ken does not account for variables, such as age, that could also influence one's ability to recall these events, age could be considered a(n) ________ variable.

Some critics argue that the violation-of-expectation method is flawed because

A) it is difficult for observers to discern when babies have habituated to the familiar event. B) this method cannot be used with young babies or toddlers, who easily become fatigued. C) babies make only subtle changes to their behaviors when they recover to a new stimulus. D) it reveals only babies' perceptual preference for novelty, not their knowledge of the physical world.

Which of the following statements about categorization is true?

A) Even young infants can categorize, grouping similar objects and events into a single representation. B) As infants approach their second birthday, fewer categories appear to be based on subtle sets of features. C) Older infants cannot make categorical distinctions when the perceptual contract between two categories is minimal. D) Not until the early preschool years can children sort people and their voices by gender and age.