Measuring Individual Components of Executive Processing Oliver Sawi, Zachary Greenberg, & Kenneth Paap Department of Psychology, San Francisco State University, San Francisco, CA The construct of executive processing often viewed as a set of interrelated processes all involving the prefrontal cortex, with each component recruiting other constellations of cortical function. Smith and Kosslyn (2007) partition executive processing into five subprocesses: executive attention, conflict monitoring, switching, sequencing, and response inhibition. Miyake, et al. (2000) have proposed a similar family of interrelated executive processes. This framework, in contrast to the unitary view of the central executive (Baddeley, 1986), allows for the possibility that the subprocesses have some degree of anatomical and functional independence. Consequently, one could be good at interference tasks that require only executive attention (inhibitory control) and poor at tasks that require only switching. Each subprocess can also be described with respect to how it works. For example, Executive attention can be viewed as a process that solves the problem of response competition by both enhancing the processing of goal-relevant information and inhibiting competing information. The more explicit these descriptions are the more guidance they offer in developing and testing empirical indicators of the efficacy of that process. Our principle argument is that an investigation of individual differences in executive processing should be grounded in a specific conceptual framework that elucidates the nature of executive processes and guides operational definitions for manipulating and measuring them. Furthermore, there needs to be more converging evidence that corresponding indicators from different tasks correlate with one another and, therefore, are valid measures of a specific type of executive processing. Participants The 107 participants were psychology majors at SFSU who volunteered to participate as one alternative for satisfying a class requirement. Participants have diverse backgrounds, for example, 55 were monolingual and 52 billingual. Tasks Previous Reports of Failed Convergence The absence of significant correlations between interference tasks has been reported before. Stins, et al. (2005) tested a group of 12-year old children using the flanker, Simon, and Stroop interference tasks. The correlations between these tasks were all smaller than and nonsignificant. Fan, et al. (2003) reported that the flanker, Simon, and Stroop tasks all activated the AC and the left PFC, but again, the behavioral interference-scores were uncorrelated. They conclude that "The behavioral and fMRI results taken together seem to argue against a single unified network for processing conflict, but instead support either distinct networks for each conflict task or a single network that monitors conflict with different sites used to resolve the conflict" p. 42. Keye et al. (2010) report a structural-equation analysis of the data obtained from 150 adults who participated in both the flanker and Simon task. There was no association between the two conflict factors. They conclude that "Either one or two of well established and frequently used experimental paradigms of cognitive conflict do not elicit individual differences in the efficiency of a general conflict monitoring and control mechanism, or such a general mechanism, as assumed in the conflict-monitoring hypothesis, does not exist" (p. 722). References Baddeley, A. (1986) Working memory. Oxford. Clarendon Press. Fan, J. I., McCandless, B. D., Thomas, K. B., & Posnr, M. I. (2003). Cognitive and brain consequences of conflict. NeuroImage, 18, Keye, D., Wilhelm, O., Oberauer, K., van Ravenzwaaij, D. (2009). Individual differences in conflict- monitoring: testing means and covariance hypotheses about the Simon and Eriksen flanker task. Psychological Research, 73, Miyake, A. Friedman, N. P., Emerson, M. Witzki, A. H., Howerter, A., & Wagner, T. D. (200). The unity and diversity of executive functions and their contribution to complex “frontal lobe” tasks. Cognitive Psychology, 41, Smith, E. E., & Kosslyn, S. M. (2007). Cognitive psychology: mind and brain. Upper Saddle River, NJ: Pearson Prentice Hall. Stins, J. F., Polderman, J. C. (Tinca), Boomsma, D. I., & de Geus, J. C. (2005). Response interference and working memory in 12-year-old children. Child Neuropsychology, 11, Introduction No Convergent Validity in Monitoring for Conflict or Change Across the flanker, Simon, and color-shape switching task, there are three difference scores that are used as indicators of the ability to engage in effective monitoring. Mixing Costs in switching - color-shape switching task: the difference between RTs in the pure blocks and the repeat-trials of the mixed bocks yields mixing costs. Mixing Costs in Simon and flanker subtracting mean RTs from the pure block of neutral trials from the congruent trials in the conflict block. Shifting Costs – Simon and flanker tasks: subtracting the mean of the no shift trials (two consecutive congruent trials or two consecutive incongruent trials) from the mean of shift trials. *Table 2 shows magnitude of these various indices of monitoring efficacy averaged across all participants. Table 2. Magnitude of “monitoring” indicators across the entire group. Indicator Task BaselineDifficultMonitoring Effect mixing costs Simon xxx xxx xxx shifting costs Simon xxx xxx xxx mixing costs flanker xxx xxx xxx shifting costs flanker xxx xxx xxxx mixing costs switching *The correlations between the five indices are shown in Table 3. The ten correlations are all less than and are nonsignificant despite the large n. At best, one could observe that the set of correlations hovers near +.10 and that, in general, about one percent of the variance in one indicator is shared with another. There is no compelling evidence that markers like mixing costs or shifting costs signal a general and task-independent ability to monitor conflict or to prepare for a change in goals. All participants completed a demographic survey and three computer-controlled tasks that are commonly assumed to require executive processing. Simon task. On each trial of the either a Z or ? appeared to the left or right of fixation and participants responded by pushing the corresonding key. Half of the trials were incongruent in that the spatial location of the target was opposite the location of the correct response key. These experimental blocks were preceded by a block of baseline trials where the targets appeared above and below fixation and, hence, generated no response competition. Flanker task. On each trial either a left or right pointing arrow appeared at fixation and participants were required to press the corresponding key. Half of the trials were incongruent in that the central arrow was flanked by a pair of arrows pointing in the opposite direction. These experimental blocks were preceded by a block of baseline trials where the central arrow was flanked by a pair of dashes and, hence, generated no response competition. Color-shape switching task. On each trial a single target appeared that was either a circle or a triangle and colored either blue or red. In the first block participants always made color decisions with two fingers of the left hand. In the second block they always made shape decisions with two fingers of the right hand. These two “pure” blocks were combined to provide a baseline for assessing mixing costs and switching costs. In the third block the target stimulus was always preceded by a precue that indicated if the upcoming response should be based on the color of the target or its shape. Half of the trials were “repeat” trials such that the current decision was the same as the previous one The remaining half were “switch” trials and required participants to switch from one task to the other. The difference between the mean of the pure trials and the mean of the repeat trials is the standard indicator of “mixing costs”. The difference between the mean of the “repeat” and and “switch” trials is the standard indicator of “switching costs.” Regression Models Using Demographic Predictors Eleven Predictors of Executive Processing. Objective measures: score on the Raven's Advanced Matrices test, parents educatonal level, and chronological age. Multivalued measure usually treated as a bilingual vs monolingual dichotomy. "Multilingualism" was operationally defined as the summed rated proficiency across all languages. Degree to which one engages in different types of multitasking: (a) Frequency of computer game play, (b) years spent playing computer games, (c) Frequency of listening to music/other audio while walking, running, or exercising, and (d) Frequency of listen to music or other audio while doing homework, reading, or other cognitive tasks, and (e) Frequency of talking or texting on a cell phone while doing homework, reading, or other cognitive tasks Ability to excel in team sports. Attitudes and feelings about multitasking All 11 factors were used as predictors in a stepwise multiple regression for each of the indices of executive processing available in Study 3. Predicting Individual Differences in Executive Processing. The successful models, with standardized beta coefficient, areas shown below. The stepwise criteria for probability of F-to-enter was.05 and to-remove was.10. Simon Effect (Inhibitory Control) = -.24 Ravens -.20 Music+Homework Flanker Effect (Inhibitory Control) = +.22 Multilingualism -.22 Team Sports Mixing Costs in Flanker (Monitoring) = +.31 Music+Walking -.23 Cell/Texting +Homework Shifting Costs in Simon (Monitoring) = -.21 Age Shifting Costs in Flanker (Monitoring) = Years Gaming Switching Costs (Switching) = -.47 Team Sports The step-wise regression models for indicators of various components of executive processing yield no consistent pattern that would support the assumption that they are tapping into a unified ability to engage in cognitive control. Further, the two broadly accepted indicators of inhibitory control have different pairs of significant predictors, inconsistent with the hypothesis that they both reflect a task- independent and general ability to resolve conflict. Executive Attention (Inhibitory Control). The difference between the congruent and incongruent trials in both the Simon and flanker task is used as an indicator of executive attention Both tasks yield significant interference effects that are typical in magnitude for each task. Table 1. Magnitude of the Simon and flanker effects (ms) for group analysis. TaskCongruentIncongruentInterference Effect Simon flanker Does the magnitude of Simon effect obtained for each individual predict the magnitude of their flanker effect? No! r(106) = , p =.91 The absence of an association between these two interference effects has important implications for the standard practice of using these tasks as indicators of individual differences in the ability to control executive attention. If there is no association, then only one of the two tasks could require executive attention or the inhibitory control exercised in both tasks are completely task dependent. This lack of convergence undermines the confidence that individual or group differences in the magnitude of the flanker or Simon effect signals differences in executive attention. No Convergent Validity for Executive Attention Table 3. Correlation between indicators of monitoring efficacy. Mixing Mixing Shifting Shifting Simon Flanker Mixing in Switch Task Mixing in Simon-Task Mixing in Flanker-Task Shifting in Simon-Task Indicators of Orthogonal Executive Processes The type of convergent validity that cognitive psychologists routinely seek when evaluating the construct validity of their operational definitions of abstract concepts usually involves demonstrating that the markers for two tasks correlate with each other. If the two indicators do not correlate with one another, then any pattern of results observed in both tasks is likely to indicate task specific differences rather than evidence of a shared and domain-general ability. Thus, it is informative to explore the degree to which individual differences in one indicator predict other indicators of the same executive process. The present set of three studies provides multiple markers of both executive attention and monitoring Cognitive/Neural Components of Executive Processing References