The Project
The NASA-TLX is one of the most common usability measurement methods to measure perceived workload. Due to a largely paper-based administration, and despite its popularity amongst usability professionals, I found the current NASA-TLX offerings to be severely lacking in ease-of-use. I decided to dosomething about that so I developed both a web-based version (http://nasatlx.com) and a desktop version for all researchers to use free of charge.
This was one of my first forays into building an online app. With new user sign-ups every day, and despite the limitations of using a Flash-based app, around 10k users have used this app to conduct user experience and psychology-related experiments around the world. I plan to convert this into a mobile-first app using the Ionic framework (Angular, TypeScript, CSS3, HTML5, Sencha) in the near future.
I also published a proceedings article on the rationale for creating a more usable NASA-TLX for the Human Factors and Ergonomics Society in 2011 (http://pro.sagepub.com/content/55/1/1375.abstract).
A Brief History of the NASA-TLX
The NASA Task Load Index (NASA-TLX) is a subjective, multidimensional workload assessment tool. It was originally developed by the Human Performance Group at NASA Ames Research Center over a three year development cycle that included more than 40 laboratory simulations. It is thought to be one of the most validated workload measurement tools in Human Factors Psychology and Engineering.
The NASA Task Load Index (NASA-TLX) is a subjective, multidimensional workload assessment tool. It was originally developed by the Human Performance Group at NASA Ames Research Center over a three year development cycle that included more than 40 laboratory simulations. It is thought to be one of the most validated workload measurement tools in Human Factors Psychology and Engineering.
The NASA-TLX rates perceived workload on six different scales: Mental Demand, Physical Demand, Temporal Demand, Performance, Effort, and Frustration. According to Hart and Staveland (1988), a participant should first rate the six scales according to how much they contributed to the workload required for the task being studied. After the ratings, each of the six scales is weighted. The weightings are achieved by answering 15 pair-wise comparisons and are designed to greatly enhance the sensitivity of the overall workload score while reducing between-rater variability.
The pair-wise comparisons component is only needed after each distinctly different task. When completing similar tasks, it was found that the comparisons did not significantly add to the overall sensitivity of the tool. Some schools of thought go as far as to suggest that the pair-wise comparisons are never needed. This online and desktop version of the tool lets you select the method that best suits your preferences.
