Debbie Dalke, a Ph.D. candidate (at Penn State University ) conducted a study to investigate several factors which might provide insight into the gender differences which are so consistently reported in water-level studies. She recruited *n* = 166 subjects (all college students) from introductory psychology classes. Each subject was given two test booklets. The first was a paper-and-pencil water-level test. This consisted of six drawings of a rectangular glass tipped at one of three different angles on a table top (20, 40, and 60 degree degrees; three tipped to the left and three tipped to the right). A line representing the table top was located beneath the glass (see pictures below). The subjects were told to "Imagine that the glass has water in it and draw a line which represents how the surface of the water will look". A drawing was considered to be correct if the line was within five degrees of true horizontal.

Then each subject was asked "Did you draw the water line as it would look after the glass had come to a complete halt or while it was in motion?" Answers were recorded as a variable MOVING with values "1" if the answer was "complete halt" and "2" if the answer was "moving". Finally, each subject answered questions or performed tasks, in the second booklet, on

- Gravity (5 items - example item)
- Complex Physics (4 items - example item )
- Mental Rotations (Vandenberg's test-6 problems, 2 answers/question).
- Drawing a line inside a triangle; the variable measured was the deviation in degrees from a horizontal line.
- Estimating the intersection of two lines (Bryant's test-3 tasks. Subjects were given 2 points if the "dot" was within 3mm of the intersection, 1 if within 5 mm, and zero otherwise, on each task).
- Drawing a "light-cord" hanging from the ceiling of a trailer going up a hill, slanting either left or right, at angles of either 20 or 40 degrees.
- Drawing a "tree" on the side of a hill, inclined 20, 40, or 60 degrees in both left and right directions. Subject's answers were scored as correct if the drawing in (f) or (g) was within 5 degrees of true vertical.