Headline #1: low self-esteem shrinks brain as a casual reader of this headline, you might then conclude that the relationship between the variables is:

Positively correlated

This means that self-esteem and brain size is correlated, because as one decreases, so does the other. Positive correlation is simply the relationship between two variables, such that their values move in tandem - that is, they either increase or decrease together. Another example of positive correlation is the relationship between age and height in children. That means as age increases so does height and vice-versa.