- With an estimated 5.4 million Americans living with Alzheimer’s disease facing
individual, social, and financial burdens, researchers must make cognitive assessment inquiries a priority (Alzheimer’s Association, 2016). Cognition encompasses multiple aspects of thought
processes, such as multiple types of memory, planning, inhibitory control, attention, and
processing speed. The higher level cognitive processes, collectively known as executive function (EF) abilities, are widely recognized as the components of cognition most likely to show age-related declines (Jurado & Rosselli, 2007).
This thesis study features a new way of measuring EF in community dwelling older
adults through the adaptation of a well-known measure of EF in children, the Head-Toes-Knees-Shoulders task (HTKS; McClelland & Cameron, 2012). The HTKS is a game-like task
administered between participant and examiner designed to measure EF abilities of working
memory, cognitive flexibility, and inhibitory control by assessing participant’s responses to a
maximum of four paired behavioral rules: “touch your head” and “touch your toes;” “touch your
shoulders” and “touch your knees.”
Under life span developmental theory’s selection, optimization, and compensation model,
(SOC; Baltes, 1997), the underlying goals of this thesis were to 1) determine the reliability and
validity of the HTKS when administered in an older adult sample, and investigate the 2)
personality characteristics and 3) strategy processes related to better performance on the task.
First, we hypothesized good internal consistency, good convergent validity as compared to the
NIH Toolbox: Cognition Battery (Gershon et al., 2013), and good discriminant validity as
compared to the Positive and Negative Affect Schedule (Watson, Clark, & Tellegen, 1988).
Second, we hypothesized higher levels of neuroticism would be related to poorer HTKS
performance, and higher levels of openness and agreeableness would be related to better HTKS performance. Third, we hypothesized older adults would use some form of strategy when
completing the HTKS, and higher levels of SOC-related strategies as measured by an open-ended strategy question and the SOC questionnaire (Baltes, Baltes, Freund, & Lang, 1995) would be related to better performance on the HTKS.
A sample of 150 community dwelling older adults (M = 68.55 years of age, SD = 6.34
years of age, 72% Female) was recruited to participate in a scheduled hour of cognitive testing.
Among these participants, the HTKS total score had an unexpected ceiling effect, possibly due to the relatively healthy and highly educated characteristics of the sample. Due to the ceiling effect and little variation in HTKS total score, we utilized an additional variable named HTKS
completion time that allowed for the study of an additional element of cognition, speed of
processing. Completion time allowed for a measure of HTKS performance with more variability
and provided a way to measure speed of processing via timed completion of the task.
Good internal consistency for the HTKS was demonstrated by Cronbach’s alpha of the
overall HTKS task (α = .84) and its inter-item α range (.82 – .84). Bivariate correlations between the HTKS variables (total score and completion time) and individual scores on the NIH Toolbox: Cognition Battery were used to assess convergent validity. Correlations between the HTKS and NIHTB measures were strongest for completion time (not total score) as the measure of HTKS performance. EF processing as measured by HTKS completion time was associated with better processing speed (r = -0.30), attention (r = -0.21), and inhibitory control (r = -0.20), but not working memory. When using HTKS total score, better EF functioning as measured by HTKS total score was associated with better processing speed (r = 0.24) and attention (r = 0.17), but not inhibitory control or working memory.
Both HTKS completion time and total score were unrelated to positive and negative affect (all ps > .05). The consistency of this pattern of no-association between HTKS variables and affect is in support of our hypothesis and demonstrates good discriminant validity.
Partial support for the personality hypothesis was found. After adjusting for demographic variables, emotional stability and conscientiousness related to better HTKS performance as measured by HTKS completion time, and higher levels of agreeableness were associated with lower HTKS total scores.
As hypothesized, 84% of the sample reported using some kind of strategy while completing the HTKS (36% employed SOC-related strategies). After adjusting for demographics, there were no significant relationships between SOC use and HTKS. Contrary to the hypothesis, HTKS performance was not related to any subscale on the SOC questionnaire.
This thesis study provides evidence for the HTKS as a reliable and valid measure of EF in a community dwelling older adult sample. We argue these findings pave the way for future studies to examine the HTKS as a potential new and effective MCI and dementia screening instrument. The HTKS is a brief, low-cost, easy to administer instrument that incorporates motoric engagement in ways that existing cognitive screening tools do not.