To achieve high-quality results you will have to be knowledgeable in sensory testing and want to observe the following
Calibration to the screen resolution
Enter the length of the blue ruler on the Settings screen (in millimeters). This is automatically saved by FrACT and needs only to be repeated when changing screens or resolution.
Enter on the Settings screen (in centimeters), and be sure it’s large enough to avoid ceiling effects, see the Manual [PDF]. If “max. VAdecimal” and the numbers around it do not turn red, you’re safe. This setting is saved by FrACT.
Luminance of the visual display unit
DIN and ISO norms prescribe a range 80–320 cd/m², easy to achieve with current display units
Luminance of the surround
The surround requirements depend on screen size. If screen ≥ 10°: not darker than 1% of the screen; for smaller screens: between 10% and 25% of screen luminance.
Luminance linearity of your visual display unit
- For acuity: not very important. Ignore, or go to
Settings>Luminance linearisation and use the top two buttons for linearisation
- For Vernier: semi-important. Perform the simple calibration mentioned above
- For contrast thresholds: very important. Best to use a screen calibrator (these have become very inexpensive, e.g. Datacolor’s Spyder), calibrate the screen to a gamma=1.0, and enter that gamma value of 1.0 in the box at
Settings>Luminance linearisation>gamma value.
- You can also use a screen calibrator to set the system to another gamma value (e.g. 1.8); if so, then enter that value in FrACTs gamma box.
- This setting is automatically saved by FrACT.
Semiautomatic export of results → spreadsheet
- Select the correct decimal mark (comma or period) for your locality in Settings, bottom right. (Important, otherwise Excel might interprete your results as dates!)
- Decide whether you only want the final result or the full history (with reaction times etc.) and select in Settings
- Start the spreadsheet program (e.g. Numbers or Excel) beforehand, add additional information you might want and switch between FrACT and spreadsheet with the task-switcher shortcut (⌘-tab for Macs, alt-tab for Windows)
- After each test run, switch to the spreadsheet and paste. Voilá!
Remote keypad for response entry
- This proved very useful!
- If you are using a remote keypad for response entry, make sure it is oriented correctly.
Switch off keyboard repeat (otional)
This avoids unwanted responses, caused by prolonged pressing of a key. How to do this:
- Mac OS X:
System Preferences>Keyboard>Keyboard>Key Repeat “Off”
- Windows XP (English):
Start>Control Panel>Accessibility Options>Use FilterKeys
Tick it, go inside and tick “Ignore repeated keystrokes”
- Windows XP (German):
Tick this checkbox, then go inside and tick “wiederholte Tastenanschläge ignorieren”
- Windows 7: Start>Control Panel>Keyboard: Repeat delay “long”, Repeat rate “slow”.
To turn it off completely, you need to go to
Start>Control Panel>Ease of Access>Set up Repeat Keys…>Ignore all repeated keystrokes
Binocular training run
Running a binocular training run with your subjects has proven useful. The participants can familiarise themselves with the test, and you can explain the “forced choice” situation, e.g.: “use your best guess, even if you don’t see it!” Usually, I don’t even analyse the results of this run.
“Whoops, pressed the wrong key”
When the subject reports “whoops, pressed the wrong key” during the first 3 trials: It’s best to abort by pressing “5” twice and restart this run.
Much more detail in the Manual [PDF]