The written Trail Making Test (WTMT; Army Individual Test Battery, 1944
; Reitan, 1955
) is a visuomotor speeded task consisting of two parts that is a widely used neuropsychological measure among clinicians (Rabin, Barr, & Butler, 2005
). WTMT-A is a simple visual scanning task that requires one to draw a line connecting consecutive numbers from 1 to 25. WTMT-B adds the dimension of dividing one's attention between unrelated conceptual sets, requiring one to draw a line connecting numbers and letters in alternating sequence. Factor analytic studies have indicated that rapid visual search, contextual set shifting, and visuospatial sequencing are major components of WTMT-B performance (Des Rosier & Kavanaugh, 1987
; Fossum, Holmberg, & Reinvang, 1992
). However, non-cognitive factors such as poor vision and impaired motor functioning are known to impact performance and can preclude test administration in some instances. This problem is commonly encountered among older patients, persons who have sustained orthopedic injuries, and patients experiencing certain neurologic conditions (e.g., individuals whose dominant limbs are hemiparetic following a stroke).
An oral version of the TMT (OTMT) developed by Ricker and Axelrod (1994
) removes the visual and motor components of the task in order to allow for the assessment of those who are unable to complete the standard written form. The sample in the original study included 58 healthy adults who were divided into three age-groups. Results suggested significant between-group age differences using analysis of variance (ANOVA). Subsequent post hoc analysis revealed significant differences between the youngest and oldest age groups on both OTMT-A and OTMT-B, although no statistically significant differences were detected between the younger and the middle age groups. Further, correlational analyses revealed significant relationships between these two versions of the TMT. Overall, the authors presented the OTMT as a promising addition to the assessment of attention by acting as an oral analog for WTMT.
Although years have passed, validity studies and normative data remain sparse for this measure despite evidence that it continues to be routinely employed by many neuropsychologists (Strauss, Sherman, & Spreen, 2006
). In a recent book chapter, the original authors cite only a handful of validity studies for the OTMT, with most completed by their own group (Axelrod & Lamberty, 2006
). Validity studies have been completed in a sample of 58 healthy adults (Ricker & Axelrod, 1994
), 85 cerebrovascular accident patients (Ricker, Axelrod, & Houtler, 1996
), 86 older medical patients (Ruchinskas, 2003
), and a mixed clinical sample of 112 subjects with a wide variety of neurologic, medical, and psychiatric diagnoses (Abraham, Axelrod, & Ricker, 1996
). Results of these validity studies suggested that the OTMT was able to discriminate between patients with different lesion sites at a similar level of sensitivity as the WTMT and established some of the basic psychometric properties of this measure (e.g., preliminary exploration of the statistical relationship between OTMT and WTMT, some demographic factors, and concurrent validity).
Arguments that the OTMT and the WTMT are analogous measures have been based on the congruence of results found in these preliminary studies. In the original study, correlations between the two versions of the TMT were large and statistically significant (r
= .68 for TMT-A and r
= .72 for TMT-B). Further evidence came when using the OTMT and WTMT in various clinical populations. The Abraham and colleagues (1996)
study found an age-related effect for both the OTMT and the WTMT (with older subjects performing significantly worse than younger subjects) regardless of the patient group (normal, medical, or psychiatric diagnosis). Demographic variables including intelligence, education, and gender were not found to yield significant differences for either OTMT or WTMT among the groups. In addition, the authors found both OTMT-B and WTMT-B did not correlate well with measures of expressive language but did correlate well with measures of executive control. One study has reported an impact of education on OTMT performance in a sample of older medical patients (Ruchinskas, 2003
). However, the authors in this study acknowledged a significant difference in the education levels among the three groups, with the control group having almost three more years of education than one of the experimental groups (neurologic patients). Results yielded the level of education as a significant predictor of passing or failing the OTMT-B.
In contrast, there are enough differences between these measures in terms of obvious perceptual and motor demands to question whether they measure the same underlying constructs. The differences in the demands of these measures are backed by a failure to observe a relationship between the oral and written versions of the TMT in some studies. For example, the Ricker and colleagues (1996)
study found no significant correlation between the OTMT-B and the WTMT-B for one group of subjects (anterior strokes). This could reflect that motor deficits only hinder performance on the WTMT.
Similarly, although the initial OTMT publication found a large correlation (r
= .68; Ricker & Axelrod, 1994
) between Part A of the OTMT and the WTMT, subsequent studies have demonstrated only a weak to mild relationship (r
= .10–.29; Axelrod & Lamberty, 2006
). Although WTMT-A requires visual scanning and psychomotor speed, the OTMT-A is really more of an overlearned, mental control task that places no demands on visual or motor functions. Creating a true analog of WTMT-A appears virtually impossible, as one cannot develop an oral sequencing task that parallels the written version.
There have also been some limitations in the existing validity studies primarily due to restrictions in sample characteristics, and normative data for the OTMT remain scant. The three groups used in the original Ricker & Axelrod (1994)
study had a narrow demographic profile that placed considerable limitations on its normative properties. More specifically, Ricker and Axelrod's (1994)
sample had a significant gap in the middle to older age ranges, with the age range from 40 to 70 years not well represented (i.e., the sample included college students and persons living in a retirement community). Because they were comparing groups at extreme ends of the age spectrum, it appears that this could bias their sample toward finding age-related correlations. The 112 subjects used in the Abraham and colleagues (1996)
study suffered from a breadth of medical conditions with relative small sample sizes within each group to yield a very heterogeneous population, making the generalization of findings difficult. Although the convergent validity of OTMT appears promising in clinical populations, its psychometric properties within the normal population are tenuous given the limited normative information.
The purpose of the present study was to further examine the potential clinical use of the OTMT. The relative ease of administration, coupled with its potential applicability to populations with visual and/or motor limitations, makes it a viable instrument for use in a variety of clinical contexts. Yet to date, there have been no follow-up studies evaluating its psychometric properties in a nonclinical sample that is more evenly stratified by age. Therefore, we sought to explore relations between demographic variables (i.e., age, education, and gender) and performance on the OTMT. In addition, concurrent validity of the OTMT with WTMT was evaluated, and normative performance provided for the OTMT to make is useful for clinical comparison.