An Introduction to PEBL: The Psychology Experiment Building Language

Abstract

PEBL (Psychology Experiment Building Language) is a new programming language developed especially for building psychology experiments involving human participants interacting with a computer. PEBL source code and compiled binary executables are available via the internet at http://pebl.sf.net. Technical Details PEBL is an interpreter/compiler written in C++, and uses a parser designed with the flex and yacc compiler design tools (Levine et al., 1992). PEBL makes heavy use of data structures from the C++ Standard Template Library, and uses a countedreference pointer system to enable automatic memory management. It is designed with several principles in mind: (1) The source code for important scientific tools should be freely available and modifiable; PEBL is Free software, allowing experimenters complete control over the system. (2) PEBL is designed to be cross-platform, allowing a single program to run on whatever computer system the interpreter is compiled for, and to allow today's experiments to be used on tomorrow's computer systems. (3) PEBL is designed to be used by psychologists, who are rarely skilled programmers. Consequently, aspects of the language are designed to enable common experiment idioms to be used easily, while having a forgiving syntax that encourages the creation of maintainable and readable programs. PEBL is Free Software PEBL is designed with the hope to providing a lingua franca within which psychology experiments can be created and exchanged freely, to be used without the need to license or purchase other software. The source code for PEBL is licensed under the GNU General Public License (Stallman & Moglen, 1989), which allows others to use and modify the source code as long as any changes are made available to others. The license covers distribution of the executable binaries and source code of the PEBL system, and does not include usercreated experiments that can be run with PEBL. Psychologists who design experiments using PEBL are encouraged to redistribute their PEBL programs freely, to foster easier exchange of scientific information. PEBL is Cross-Platform. PEBL was designed to allow it to be easily ported to different computing platforms. Together with the fact that Current versions are written using the Simple DirectMedia Layer Libray (SDL; Lantiga, 2004) an open source cross-platform game library. The use of this library enables multiple platforms to be targeted easily, but PEBL Paper read at the 34th annual meeting of the Society for Computers in Psychology (SCiP), November 18, 2004, Minneapolis, MN.