NASA Task Load Index (NASATLX)FREE for use with an Inquisit Lab or Inquisit Web license.
Available Test Forms
Hart, S. G., & Staveland, L. E. (1988). Development of a multi-dimensional workload rating scale: Results of empirical and theoretical research. In P. A. Hancock & N. Meshkati (Eds.), Human mental workload, 139-183. Amsterdam, The Netherlands: Elsevier.
Beyers, J.C., Bittner, Jr, A. and Hills, S.G. Traditional and raw task load index (TLX) correlations: are paired comparisons necessary? Advances in Industrial Ergonomics and Safety I. London: Taylor and Francis, 1989.
Wierwille, W.W. & Eggemeier, F.T. (1993). Recommendation for mental workload measurement in a test and evaluation environment. Human Factors, 35, 263-281.
Hitt II, J.M., Kring, J.P., Daskarolis, E., Morris, C., & Mouloua, M. (1999). Assessing mental workload with subjective measures: An analytical review of the NASA-TLX index since its inception.