The traditional SART task requires key presses to all digits appearing on the screen. However, the key press should be withheld if the digit is a 3

When aggregating the collected data, what is considered an error?

Is it simply the number of times the key was pressed when a 3 is on the screen? Or does it also include incorrectly withheld key presses (i.e. when the digit is anything other than 3)?


1 Answer 1


Both are errors indeed. Pressing when a 3 is shown is called a false alarm, and not pressing when a three is shown is a miss. Correct responses are (1) hits (pressing when anything but a three is shown) or (2) correct rejections (not pressing with a three).


These classifications are used in signal detection theory (Wiki). More specifically, they are used to calculate sensitivity and bias.

Sensitivity, or d-prime (see also other questions on CogSci, e.g. Calculating d-prime), is the metric for how well one can distinguish targets from distractors. Bias, on the other hand, is:

the extent to which one response is more probable than another (Wiki)

  • 1
    $\begingroup$ I realise that they're both errors, but are they both used in the error calculation that is typically published? The original Robertson paper isn't explicit about this, but I get the sense they are only considering false alarms in their results $\endgroup$
    – Simon
    Commented Feb 5, 2017 at 9:13
  • $\begingroup$ I made some minor changes to my answer in hope to clarify my answer. I don't work with it myself, so I don't know of any recent literature and their practices, but I hope my answer may give you some starting point for your search. $\endgroup$ Commented Feb 5, 2017 at 9:59

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