Introduction

28 participants performed a simulated manufacturing task where they were insructed to build a Lego set like that in figure 1.

# the out.width command is for external files (like in this case). It resizes the original image.

# all required packages need to be installed
library (knitr)

knitr::include_graphics("https://i.etsystatic.com/12951250/r/il/946bcc/1438475524/il_570xN.1438475524_sefc.jpg")

# to add the external image, we use the include_graphics of knitr

Figure 1. Image of Lego set used in the experiment.

Concurrently to the manufacturing task, they also performed a secondary task called n-back (Owen, McMillan, Laird, & Bullmore, 2005). Three version of the n-back were performed:

  • Control
  • 0-back
  • 2-back

The dependent measures were:

  • Manufacturing task performance
    • Completion Times
    • Accuracy
  • EMG (Mehta & Agnew, 2011)
    • mean EMG
    • integrated EMG


* Self-reported workload (Mansikka, Virtanen, & Harris, 2018)

Objectives

The study has the following objectives:

  1. Determine the effect of completing a cognitive task on manufacturing task performance
  2. Determine the effect of completing a cognitive task on muscle activity

Results

Manufacturing Task

# the command above tells R not to show any warnings or possible other messages in the output file

# The one below is a very important function. Instead of scripting your code in the rmd file, you tell R to load a separate file that has all your code. This way you don't have to clutter the rmd file. 
# To use this command without errors, you need to make sure that:
# - your source code is in the folder as the rmd file
# - your source code has no errors
# - your source codes uses unique names for different objects (e.g., plots etc.). This is to avoid R from calling the wrong objects

source("CogLoadManuf_Rscript.R") #Get the functions for loading the data

Manufacturing Task completion times were averaged across conditions. Figure 1 presents the manufacturing task completion times as a box plot.

# here we use the fig.width command because we are using a plot created by R (not an external file like we did above)
plot_Man

Figure 1. Manufacturing task completion times

EMG data

Integrated EMG was calculated for each of the 7 muscles across the 3 experimental conditions (control, 0-back, 2-back). iEMG for each muscle is presented in FIgure 2.

plotEMG

Figure 2. iEMG by muscle and experimental condition

Self-reported workload

Average NASA-TLX ratings are presented in Table 1.

knitr::kable(data2TLX)
Condition Mental Physical Temporal Success Effort Frustration
NA NA NA NA NA NA
0-back 4.193548 3.161290 4.096774 5.483871 4.774193 3.00000
2-back 8.321429 3.892857 6.642857 6.357143 7.178571 6.25000
control 2.593750 2.906250 4.343750 5.718750 4.406250 2.46875
Table 1. Ave raga NASA-T LX ratings across cond itions

References

Mansikka, H., Virtanen, K., & Harris, D. (2018). Comparison of NASA-TLX scale, Modified Cooper-Harper scale and mean inter-beat interval as measures of pilot mental workload during simulated flight tasks. Ergonomics, 0(0), 1–22. https://doi.org/10.1080/00140139.2018.1471159

Mehta, R. K., & Agnew, M. J. (2011). Effects of concurrent physical and mental demands for a short duration static task. International Journal of Industrial Ergonomics, 41(5), 488–493. https://doi.org/10.1016/j.ergon.2011.04.005

Owen, A. M., McMillan, K. M., Laird, A. R., & Bullmore, E. (2005). N-back working memory paradigm: A meta-analysis of normative functional neuroimaging studies. Human Brain Mapping, 25(1), 46–59. https://doi.org/10.1002/hbm.20131