A correlation matrix concisely presents Pearson's $r$ values among multiple variables, such as working memory, executive function, and age. The variables are listed sequentially down the leftmost column and across the top headings. Because any variable perfectly correlates with itself ($r = 1.00$), the diagonal cells are conventionally filled with dashes. To prevent redundant information, the table only displays the computed correlation coefficients in the bottom half of the matrix, leaving the mirrored upper half blank.