Marilena,


When it comes to presenting stimuli, MediaLab uses seconds as the unit of time the user can program. You can find more information about this using the duration parameter here in the MediaLab manual: http://www.empirisoft.com/medialab/h...s.htm#duration.


There is a nice summary comparing DirectRT and MediaLab here in the DirectRT manual: http://www.empirisoft.com/directrt/h...y_concepts.htm


I've copied the text below if you would just like to read that information:


"DirectRT or MediaLab?


Many users ask us if they should use MediaLab, DirectRT or both. Whether you use one or both depends on what your needs are. MediaLab's strength is in its flexibility and ease-of-use with respect to traditional self-report questionnaires (many closed and open-ended question formats) and multi-media stimuli (movies, sound, html, word documents, powerpoint shows, etc.). You can use its point-and-click interface to quickly create an attractive questionnaire or experiment. It also creates data files in a horizontal (one row per subject) format that are very easy to work with and ready to analyze in Excel or SPSS. All of MediaLab's multi-media flexibility requires that it be a traditional Windows program, meaning that the any measures of display and response timing are also subject to the variations of the Windows operating environment. Thus, projects involving tasks like cognitive/perception trials (e.g., priming/lexical decision style tasks) that require measures of stimulus presentation and response times reliable and accurate to the millisecond are not as well-suited to MediaLab.


This is what DirectRT is excellent for. You get total control over timing because it's a DirectX application and not a "Windows" program. Basically, it was created to do what MediaLab can't do well?high precision cognitive/perception, "blocks of trials" types of tasks. You define your trials in a spreadsheet (e.g., Excel) so you can use your favourite spreadsheet app for editing the input files (a very nice benefit). Due to the nature of DirectRT experiments, the data files are vertical (e.g., one row per trial). This means it takes a bit more skill to collapse and analyze the data. Although some tasks could be easily done with either program, one or the other is usually a clear choice.


Both programs are stand alone, but they do work very well together as complements. A lot of people use both and embed DirectRT sessions within a more general MediaLab experiment. That's the gist of the difference."


Jason