Micro Experimental Laboratory (MEL)is a third-generation integrated software system for experimental research. The researcher fills in forms, and MEL writes the experimental program, runs the experiments, and analyzes the data. MEL includes a form-based user interface, automatic programming, computer tutorials, a compiler, a real-time data acquisition system, database management, statistical analysis, and subject scheduling. It can perform most reaction time, questionnaire, and text comprehension experiments with little or no programming. It includes a Pascal-like programming language and can call routines written in standard languages. MEL operates on IBM PC compatible computers and supports most display controllers. MEL maintains millisecond timing with high-speed text and graphics presentation. MEL provides a systematic approach to dealing with nine concerns in running an experimental laboratory.Developers of any software system for experimentation must trade off considerations of flexibility, learnability, ease of use, precision, experiment generation time, and experimental qualitycontrolto maximize systemperformance. Incorporation of advances in hardware and software technology allow for quantum jumpsin termsof system performance given the above considerations. The Micro Experimental Laboratory (MEL) optimizes these trade-offs within the constraints of personal computers with640Kof memory, human factors considerations about interfacetechnology, fourth-generation software technology, and the use of automatic programming techniques.MEL is a third-generation psychology software system that builds on the lessons learned from earlier programming systems. The first generation of programming languages in psychology were typically specialized process control languages working in small memory partitions (e.g., Schneider & Scholz, 1973;Scholz, 1972) operating with less than 16Kof memory on machines such as the DEC PDP-8 or the IBM 1800. The second generation had two major variants. The first was the subroutine approach, whichinvolved a seriesof subroutines that are called from FORTRAN or Pascal programs (e.g., Osgood, 1985Osgood, , 1988) running on DEC PDP-lIs or Apple lls with 64K of usable memory per process.1 The second variant was the stimulus presentation approach (Eamon, 1982;Poltrock& Foltz, 1982, in whichfixed displays were presented in prespecified orders on Apple II computers. The orders could be either specified within one of three prescribed paradigms, as in CEDATS (Eamon, 1982), or explicitly enumerated, as in APT (poltrock & Foltz, 1982(poltrock & Foltz, , 1988. The subroutine package approach was flexible but required that graduate students be trained as programmers and involved longdevelopment timesto generate experiments. The stimulus presentation approach allowed fastexperiment specification at the costof reduced flexibility and a great deal of typing to enumerate all the stimuli and the stimulus orderings.MEL is a third-generation psychology software system that operates on IBM PCs with 640K of mem...