IEEM Human-Computer Systems Dr. Vincent Duffy - IEEM Week 6 - Mental Workload Demo Apr. 13, ieem.ust.hk/dfaculty/duffy/

Mental workload assessment v attention as a resource –searchlight metaphor - applied when information is from the same task must be combined previous information to perform the task –resource metaphor - applied when the operator must perform more than one task at a time 2

Mental workload assessment v wickens multiple resource theory- explain allocation of attention for complex tasks v assessing workload - see Cooper Harper subjective scale v also relates workload to attentional resource v other examples seen later on : workload related to predictive models such as NGOMSL, equate workload w/working memory 3

Mental workload assessment - ways to assess measures v sensitivity - ability to detect changes v diagnosticity - ability to detect which attentional resource pool is used v primary task intrusion- ex. tapping while finding problem in nuclear plant v implementation reqts. - higher for measures that include secondary tasks 4

Workload Assessment techniques v Physiological measures –ex. more workload and smaller pupil size v Subjective measures- Cooper-harper v Primary task measures –ex. speed as a function of task difficulty v Secondary task measures –serve as an indicator of spare attentional resources –choice of task should impose continuous demand on the user physiological measures 5

v please use a sheet of paper to keep track of pretest data, and data for 3 tasks v please divide your paper into 4 parts –pretest, task1, task 2 and task3 –each group should have one person with a stopwatch/seconds –please plan to do QOTD on the back of this sheet later in the class 6

Find the subject v How familiar are you with Microsoft Excel spreadsheet? v (lowest) (highest) v How many hours have you used MS- Excel in the last 1 month? v more than 50 v in the last year? v more than 50 v Who is most expert in your group? 7

v Subject is the person with the lowest expertise 8

Demo v Task 1 –determine the subject, open excel spreadsheet –ready to begin? –other group member (observer) count/measure time to complete (no task longer than 5 min) –subject type the following numbers in column A –14579, 15834, –find the sum (total) of the numbers –use help if you are not sure how to do it v subjects come up front –administer Cooper Harper afterward 9

Task 2 v observer count/measure time to complete (no task longer than 5 min) –hum your national anthem –subject type the following numbers in column B : 16457, 61584, –find the standard deviation of the numbers –use help if you are not sure how to do it –keep humming v subjects come up front –count errors (any stop in humming) 10

Task 3 v observer count/measure time to complete (no task longer than 5 min) –hum your national anthem –subject type the following numbers in column C : 56167, 56144, –use the chart wizard (see icon) to graph the numbers –keep humming v subjects come up front –count errors (any stop in humming) –administer Cooper-Harper afterward 11

QOTD - What are we testing and how? v Q1. What is a hypotheses for this demo? –This demo is not about humming –it is about mental workload v skip to measures v Q2. What are primary task measures? –time –eg. Speed as a function of task difficulty v Q3. What are secondary task measures? –no. of errors (during humming) 12

QOTD continued –The secondary task measure helps you determine/indicate… –spare attention resources –eg. Errors made, slowed down, etc. v Q4. What are post-task measures? –Modified cooper harper mental workload measure v Q1. What is a hypothesis for the demo? –How does mental workload change w/changing task (difficulty). 13

v Q5. How would you test the hypothesis? –With a t-test or anova? –What would you compare? –Therefore which analysis…t-test or anova? T-test using comparing task 2 and task 3 (errors and task time) –why not task 1 also? 14

v Why should the hypothesis not be…. –Additional task (humming) causes higher mental workload –yes it may, but task 1 and task 2 are different (sum and std. Deviation). As well, task 1 has no secondary task and task 2 has humming, so you can’t compare –there is a confound so task 1 can not be compared to task 2 (and can not be compare to task 3 either)

v Why should the hypothesis not be…. –Humming causes the task to take longer? –Though it is true, the humming of the song is done only to help compare ‘spare resources’ ….comparing task 1 and task 2 (with or with out humming….again will have a confound since task 1 and 2 are different).

–Really…in order to get a comparison of mental workload and task difficulty, you only want to compare task 2 and task 3 (to get the difference in errors in humming in task 2 compared to the errors in humming during task 3)…having the modified cooper harper in task 2 would be useful, but then you don’t need the if you had the modified cooper harper. You can use an anova, but t-test is sufficient (since there are only two groups/tasks to compare).

Homework v Wk10- Read chapter 4 in Eberts p.61-81for next week. v Wk11- Read Chapter 5 in Eberts p (only the parts that were cover in lecture). v Week 12 - Read chapter 10, p and Chapter 11, in Cody and Smith. v Papers for wk 12 & wk13 - images reserve –Week 12 - Read paper Molnar, K.K. and Kletke, M.G., 1996 u ‘The impacts on user performance and stisfaction of a voice based front-end interface for a standard software tool’,. Int. J. of Human- Computer Studies, 45: –Week 13 - Read paper by Chi, C.F. and Lin, F.T., 1998 u ‘A comparison of seven visual fatigue assessment techniques in three data acquisition VDT tasks’, Human Factors, Vol. 40, no.4,