Visual method

In the visual method we lay trials out in one or more tables in a spreadsheet. You can use any Excel-compatible spreadsheet app—Google Sheets is most common since it gives you dropdown menus and quick docs. Rows are trial definitions. Columns are object properties. Values are MATLAB values or expressions. You only need to define each distinct trial once, and in any order. Then use a MATLAB expression to set a list of trial definitions to run through, including any repetition and ordering. Save or export to an Excel file. Then in MATLAB use the command loadExperiment to load it, and runExperiment to run.

For example, the two tables below would make an experiment that runs two repetitions of three distinct trials, all in random order. In each trial, a picture of an animal shows at a height of 10 degrees visual angle. The picture stops showing when the subject presses any key. Experiment results report picture file name and response latency for each trial. (This is an extremely minimal example! See examples and demos for more.)

Coding method

In the coding method the concepts are the same but we write a MATLAB script to build the experiment. This gives you all the flexibility of MATLAB, which may be needed for complex experiments. That said, it's not really code in the usual sense, more like a list of statements setting parameters. You can use for loops through conditions to automate defining trials. (Also note it's still possible to work semi-visually in the coding method using an optional tool sheet2vars.)

Here is the same experiment as above:

(Without PsychBench)

Just for comparison, here is some compact Psychtoolbox code that would run the same experiment, with the same timing precision and error handling. The difference with/without PsychBench is noticeable here but it balloons up for more realistic experiments.

If the library doesn't have the stimuli you need for an experiment, you can write your own code in MATLAB + Psychtoolbox. The approach is to write it as a new object type in your library—this allows you to use the code anywhere and have it work with all core functionality (timing, core visual options, staircasing, results output, etc.). You can make a quick type, or you can make a durable type with more flexibility and a fuller interface for other users. All the standard types that come with PsychBench are open source, so you can use them as examples and/or build off them.

Sharing object types

You can share an object type with other people just by zipping the type's folder and emailing it.

You can also contribute a type to the library that comes with PsychBench. If you would like to do this, please contact us. We would be happy to credit you. And thank-you!