Fig 1.
Tasks and their order during a trial—reading and memorising an example sentence Think about your skills, competence, qualifications and experience., typing from memory and reporting the perceived effort during the completed task.
The blue text during the reading task displays the sentence to be typed. When the typing task starts, the sentence to be memorised disappears.
Fig 2.
Design of the experiment during one day consisted of two sessions and a total of ten trials.
Data Analysis was divided into two parts—prediction of the fatigue level, correlation analysis and linear mixed model of the data for effects of time-on-task and perceived effort. Trials 1,5 and 10 were used as representative of the users’ state before and after sessions 1 and 2, respectively, and employed for the prediction and correlation analyses. All trials were used for the linear model.
Table 1.
Data category and features used to analyse data, and their definitions.
Fig 3.
Subjective fatigue levels—Initial (without pattern), intermediate (lined) and terminal (dotted), for the two different orders of easy (orange) and difficult (purple) sessions.
Error bars indicate standard error.
Table 2.
Model validation based on 80% training data.
Table 3.
Model results based on 20% testing data.
Fig 4.
Effect of time-on-task on (a-e) performance and (f-n) eye-based features across all subjects and days for each of the 10 trials representing time-on-task.
Error bars indicate standard error. RTE: Read text events ration, ANSR: Attended but not selected ratio.
Table 4.
Linear mixed effects model results indicating the main effects of perceived effort, time-on-task and day.