1. Background
Shallice (1982) developed the Tower of London (TOL) task as a measure of planning
ability, although the task also makes demands on attention-concentration and sequencing
ability. The test is sensitive to left anterior lesions of various etiologies in adults (Shallice,
1982), as well as to head trauma in children (Levin et al., 1993). Despite its apparent
clinical usefulness in the evaluation of executive or “frontal lobe systems” functioning,
Shallice’s TOL task lacks readily accessible normative standards for adults of diverse
cultural backgrounds.
Method
The TOL consists of three colored wooden beads which can be moved on three wooden
pegs as depicted in Figure 1. The task is to move the beads from a starting position, one
at a time, to match a stimulus configuration in the least number of moves. There are
twelve trials total at three levels of increasing difficulty: 2-3 moves required, 4 moves
required, and finally 5 moves required.
Subjects (n=18) were undergraduate students with a mean age of 22 (SD=6.63), and a
mean education of 13 years (SD=1.29). There were 11 males and 7 females. Subjects
were racially diverse with White (n=2), Black (n=6), Hispanic (n=5), Asian/Pacific (n=3),
and multiracial (n=2) subjects represented.
Results
Normative data are presented in Table 1. The number of Trials to Solution increased as
problem complexity went from 2 or 3 moves, to 4 moves, or 5 moves, F (2,34) = 11.06, p
<.05. Impulsivity as measured by Initial Planning Time was moderately correlated with
both a lower Percent Solved Trial 1 (r = .45, p<.10), and with a greater number of Trials to
Solution (r=-.49, p<.05).
Table 1: Normative performance
Mean SD
% Solved Trial 1 0.70 0.12
Trials to Solution 1.43 0.20
2-3 Moves 1.15 0.17
4 Moves 1.51 0.35
5 Moves 1.65 0.43
Initial Planning Time 5.25s 3.24
Solution Time 11.69s 5.71
Normative Standards for the
Tower of London in a Diverse Sample
Daniel Capruso, PhD & Jesam Usani
CUNY New York City College of Technology
Starting Set Solution
Move 1 Move 2
Move 3 Move 4 Move 5
Starting Set
Discussion
In a diverse urban sample, TOL performance had neither basement nor ceiling effects. Performance levels
decreased as problem complexity increased from 2 to 5 moves. Impulsivity did appear to be a factor in
performance, as shorter Initial Planning Times were associated with an increased commission of errors and
a greater number of Trials to Solution.
Presented at American Academy of Clinical Neuropsychology
12th Annual Conference, New York City
June 26, 2014
Funded by Emerging Scholars Program of NYC College of Technology
Figure 1: Sample 5-move problem on Tower of London.