At NLR human factors research is being conducted to optimize the relationship between man and machine. Emphasis is placed on the verification of interface design and usability given suitable operating procedures. To this end flight simulators (both military and civil) are used to create relevant circumstances to be able to assess pilots' performance in simulated conditions. Besides performance measures, observational and physiological measurements are also used. "Standard" physiological measurements include the heart rate and its variability, and eye activity through EOG and eye-tracker measurements. Observational measures concern the operators' applied task strategy and focus (tasks being attended to).

The total set of measures (performance, observations and physiological) allows to estimate the functional state of the participants. Besides the off-line analysis for interface usability, two different lines of research are being followed, both utilizing the developed real-time state determination methods. The first line of research uses the determined functional state to optimize the actual working conditions for the operator by delaying or altering the modality or location of less important interrupts whilst keeping a queue of outstanding tasks and messages. The second line of research focuses on the feedback of the actual user state to optimize operators' behavior by providing attention getters for salient information which has not been attended to, provision of background information (e.g. when the user is searching for information), assistance for optimization of workflow and task strategies, etc.

Since having a reliable estimate of the actual user state is a precursor for the effective use of system adaptations including optimized training, this presentation focuses on the functional state determination of operators working in simulated environments.