This dissertation employs a laboratory experiment to test the hypothesized
relationships. Figure 1.5 provides an overview of the general approach this research takes to design the experiment. First, appropriate incentives need to be identified so that the participants can be motivated to perform at a high level. Next, an experimental task has to be identified to which such major aspects of our research model as working memory and sustained attention requirements are relevant. Third, with the purpose of examining interactions between interruption design, frequency, and age, an appropriate design type needs to be identified that allows us to manipulate such interruption attributes as the color and the frequency of incoming interruptions. Further, it is important to determine a sample size that yields sufficient statistical power. In addition, the experimental procedures and manipulations have to be established, along with the measures for non-manipulated constructs and the plans for the pre- and pilot-tests.
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Figure 1.5 Overview of the Methodological Development
We use a lottery with valuable prices to motivate our participants to perform well in the experimental task and ensure that the task has meaning to them. Concerning the experimental task, we employ the online browser memory game Concentration, which has previously been used in research on age-related differences in cognitive functioning (e.g., Schumann-Hengsteler, 1996). In the Concentration task, subjects have to find matching pairs of symbols by flipping computer-generated cards. In the process, they have to memorize the symbols they have seen and where the symbols are hidden. To ensure that T-M interruption can quickly and substantially reduce the working memory capacity available for the Concentration task and easily interfere with the information
Identification of a
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processing necessary for the task, we use arithmetic and design cards specifically for this task. One card contains an integer number, and another card contains a matching
multiplication that yields this integer number. For example, a matching pair of cards could consist of one card with the symbol “15” and another card with the symbol “5 * 3.”
T-M interruptions appear on the screen within specific time intervals.
This dissertation uses a within-subjects design with two levels per factor, allowing us to clearly delineate any moderating influence of these factors without unreasonably inflating the experimental design. Since neither the relationship between adult age and inhibitory effectiveness nor the one between feature salience and attentional capture is considered to be curvilinear (Darowski et al., 2008; Yantis & Egeth, 1999), employing middle groups for these factors would not enhance our understanding of their interaction with the frequency of incoming interruptions. Using this design requires a sample size of 90 participants to yield adequate statistical power.
Consistent with the literature on the Inhibitory Deficit View (e.g., Hasher et al., 1991; Zacks & Hasher, 1997), this dissertation uses two age groups: younger and older people. Also consistent with the Inhibitory Deficit Theory, we define as younger those people between 18 and 27 years of age and as older those between 60 and 85. As regards the salience of T-M interruptions, color as a design features associated with stimulus-driven attentional capture is manipulated by employing a lower and a higher level.
Finally, the frequency with which T-M interruptions appear is manipulated by using two
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frequencies that allow us to examine any effect of interruption frequency on person-environment fit due to high cognitive demands, which constitute our focal interest.
Consistent with prior research in the area of age-related differences in
distractibility (e.g., Carlson et al., 1995; Connelly et al., 1991), this research uses students as representatives of younger individuals and older workers as well as retirees from the community as representatives of older adults. We recruit students from undergraduate classes at a large southeastern university by means of email, discussion boards, and announcements. Older adults are recruited from the local community through newspaper advertisements and university contacts. In the recruitment process, we provide
information regarding participation purpose, associated risks, and incentives.
This research further employs both objective and subjective outcome measures.
Measures include actual task performance, change in actual stress hormones found in saliva supplemented with individual perceptions of stress, the NASA Task Load Index (TLX; Hart & Staveland, 1988), and the STROOP color-word task (Stroop, 1935). We use these four tests to evaluate individual performance, strain, fit between mental
resources available and required for task performance, and capacity to actively disregard distracting stimuli, respectively. Collectively, these tests advance understanding of how and why T-M interruptions negatively affect employee well-being and performance, and how these effects depend on adult age.
We measure task performance as the number of matching pairs uncovered in the Concentration task. To evaluate change in stress hormones, we obtain salivary measures
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of alpha-amylase using salivettes. The NASA TLX is a comprehensive and multidimensional subjective measure of mental workload. It is a well-validated
instrument that derives an overall workload score from a weighted average of ratings on six relatively independent sub-dimensions, which relate to the interaction between a person and certain environmental demands. The STROOP task requires subjects to ignore attentionally compelling but unwanted signals and to suppress responses to these signals while working on another task. It presents color names printed in non-consistent ink colors and requires subjects to actively inhibit the printed names of colors, while selectively attending to the ink color in which the words are printed.
The experimental room is organized to control for extraneous distractions. All work tables face walls and all jalousies are closed. We further control for relevant alternative explanations pertaining to mental workload perceptions, stress, and task performance.