1. Jennifer Joyce1, Karen Davranche2
The usefulness of distributional analysis to assess cognitive control efficiency and susceptibility to impulsive reactions
Jennifer Joyce1, Karen Davranche2
1University of Limerick, Ireland, 2Aix-Marseille Université et CNRS, France
Simon Task
Materials and Method
Twenty-four participants
12 young (23 ± 2 yrs)
12 old (63 ± 2 yrs )
Experimental Conditions
Rest (30 mins)
Moderate Exercise (30 mins @ 65 % HRmax)
The Simon task
4 sets of 5 blocks of 96 trials were administered during each condition (1,920 trials ).
Set 1= During Condition
Set 2 = 5 min post
Set 3 = 35 min post
Set 4 = 65 min post
In the classical version of the Simon task participants are required to respond, as quickly and accurately, according to the color of the stimulus and inhibit the spatial location of the same stimulus. See Figure 1. Reaction time (RT) is usually reported to be shorter when relevant and irrelevant information correspond to the same response than when they are mapped to different responses. The difference between the RT during the incompatible (IN) and compatible (CO) associations is called the Simon effect.
Compatible associations
Incompatible associations
Figure 1. In this example, subjects are required to press the left button for the red color and the right button for the green color. The solid arrows (green and red) are the responses associated with the color of the stimulus and the dotted arrows (green and red) are the responses associated with the position of the stimulus.
Figure 5. Schematic representation of the design of the protocol.
Dual-route Models
The interference effect observed during the Simon task is thought to manifest due to the parallel activation of two routes of response selection with different time courses (Kornblum, Hasbroucq, & Osman, 1990). A conflict arises between an automatic and rapid response impulse along a direct route (triggered by the spatial location) and a slower, deliberately controlled response to the pertinent stimulus information (the color). The automatic activation is initially strong but gradually decreases over time with the strengthening of a slow and incremental inhibition. This suppression mechanism counteracts the automatic activation and facilitates the occurrence of the correct response.
Cognitive Control and Time Spent on Task
Distributional analyses revealed that the efficiency of the suppression mechanisms cannot be maintained for the duration of a 2 hour experimental session. The delta plot becomes less negative as time spent on task (TOT) increases. This divergence in the dynamics of the delta plot to the right reveals an impairment in the efficiency of the cognitive control, which was evident after 1 hour (after set 2). See Figure 6 A. However, analyses of the CAFs revealed that individuals are not more prone to make impulsive errors as TOT increases.
Figure 2. The Activation - suppression Model. The relevant stimulus dimension (color blue) is processed by the slow deliberate route (represented in blue) while the irrelevant location dimension (right location activating the right hand) is processed by the fast direct route (in red). Selective suppression of the location-based activation by the inhibition module (represented in purple) needs time to build up, and facilitates the selection and execution of the correct left-hand response (from van den Wildenberg et al., 2010, p. 2).
Figure 6. (A) Delta plot of reaction time, for the 1st Set (diamond), the 2nd Set (circle), the 3rd Set (triangle), and the 4th Set (square), as a function of RT deciles. (B) Conditional accuracy functions (CAFs), over the four testing periods, as a function of RT deciles.
Delta Curve
Delta plots graphically index the efficiency of the selective suppression manifests in the later phase. The delta curve corresponds to the magnitude of the interference effect as a function of the latency of the response. See Figure 3. Delta plots can be useful to detect variations in cognitive control between different groups (e.g. patient and healthy control), different conditions (e.g. rest and exercise) and experimental manipulations (e.g. speed versus accuracy instructions).
The activation - suppression model predicts that decreases in cognitive control, provided by the strengthening of a selective suppression mechanism over time, reduces the interference effect for slower RTs.
Speed Accuracy Strategy and Aging
Older adults adopt more cautious strategies than younger adults to complete the Simon task. This was evidenced by:
An initially weaker suppression mechanism which strengthened as the latency of the response increased to the point where it exceeded that of younger adults.
A significantly lower proportion of fast impulsive errors (Figure 7A).
In contrast, young people displayed a higher propensity to commit impulsive errors and this predisposition was also evident during exercise (Figure 7 B).
Figure 3. Delta plots are constructed by plotting the congruency effect size (IN minus CO) as a function of the response speed. In this example, delta plots illustrating impaired selective suppression in patients diagnosed with Parkinson’s disease (PD) (black) compared to healthy controls (white)(from Wylie et al., 2010, p. 2064).
Figure 7. (A) CAFs for young (circles) and old (triangles) adults, as a function of the type of trial. Percentage of accuracy for CO trials (full symbols) and IN trials (empty symbols), is plotted as a function of RT deciles and (B) CAFs, for young (circles) and old (triangles) adults, during exercise (full symbols) and rest (empty symbols) conditions. Percentage of accuracy is plotted as a function of RT deciles.
Conditional Accuracy Function
The conditional accuracy function (CAF) corresponds to the analyses of the percentage of correct responses as a function of the latency of the response. See Figure 4. The CAF is a powerful tool to assess the initial phase of automatic response activation and the related
susceptibility to making fast impulsive errors. Fast impulsive errors are more prevalent for IN trials compared to CO trials and for younger people compared to older people. See Figure 7.
Conclusion
A wealth of essential temporal information is gleaned from distributional analyses (CAFs and delta plots) which otherwise would be concealed within mean or median RT data. The activation - suppression model (Figure 2) used in conjunction with RT distributional analysis is a powerful framework to investigate the temporal dynamics of conflict resolution.
Figure 4. Conditional Accuracy Functions (CAFs) for two hypothetical conditions X and Y as well as for corresponding (CR) and non-corresponding (NCR) trials in a Simon task. Conditions X and Y are two arbitrary conditions, with condition Y associated with slower RTs and more errors than condition X. Conditions CR and NCR resemble conditions X and Y, respectively, but they also reflect the additional direct-activation effects of irrelevant location in a Simon task. CAFs were approximated by plotting, for CR and NCR conditions separately, accuracy as a function of mean RT for each of 10 response speed deciles (From Ridderinkhof 2002a, p. 499).
References
Kornblum, S., Hasbroucq, T., & Osman, A. (1990). Dimensional overlap: Cognitive basis for stimulus-response compatibility--A model and taxonomy. Psychological Review, 97(2),
Ridderinkhof, K. R. (2002a). Activation and suppression in conflict tasks: empirical clarification through distributiona analyses. In W. a. H. RPrinz, B. (Ed.), Attention and Performance, Vol XIX, Common mechanisms in perception and action (pp ). Oxford: Oxford University Press.
van den Wildenberg, W. P., Wylie, S. A., Forstmann, B. U., Burle, B., Hasbroucq, T., & Ridderinkhof, K. R. (2010). To head or to heed? Beyond the surface of selective action inhibition: a review. Frontiers in human neuroscience, 4(222), 1-13.