When newborns hear a sound, they increase their sucking. After some repetitions of the sound, their sucking decreases. If a change in the sound increases their sucking, we say that it produced _________________

A correlation is considered to be zero if:

one variable increases while the other decreases. there is no instance of a negative correlation. both variables increase together. no connection between the variables is seen.

According to the article Going to Pot, about adolescent drug use, when the participants in a cross sectional

study have lived through a unique and unusual time--such as the great depression, they may be different from others who will eventually be the same age as the participant. This is called a (a) cohort effect (b) ceiling effect (c) calendar effect (d) cluster effect