In the Building Sticks Task (BST), subjects are presented (on a computer screen) with three building sticks of different lengths and a goal stick. The objective is to create a new stick the same length as the goal using the three building sticks, by either adding or subtracting lengths. There are two methods for solving BST problems: overshoot - starting with a stick larger than the goal and subtracting down, or undershoot - starting with a stick smaller than the goal and building up.

This model simulates the third experiment of Lovett & Anderson (1996). Subjects in that experiment solved 90 BST problems designed to make one solution method (undershoot or overshoot) more successful than the other. In the "biased" condition 67% of problems were solved by the more successful method, and in the "extreme biased" condition 83% of problems were. Results show that, as the experiment progresses, subjects change their choice preferences on test problems for which no success/failure feedback is given. (Test 0 occurs before any training problems; Test 1 occurs after 30 training problems; Test 2 occurs after 60 training problems; Test 3 occurs after 90 training problems.)

ACT-R Model