Task Details

 

The digit span task is a simple short-term memory measure that involves the storage and recall of digits in correct serial position. For any given span size (n) the participant will be shown n digits that are randomly selected between 10 and 99. At the end of the presentation phase the participant is given the recall screen which requests that the participant input the numbers one by one in the order they recall seeing them.

Screenshots

 

Presentation Phase

Image shows a 
			screenshot of what the program looks like while delivering the presentation phase of 
			the task

Recall Phase

Image shows a 
			screenshot of what the program looks like while delivering the recall phase of the 
			task, asking for the first number they recall seeing

The XML

 

You can download the default XML on the downloads page. In this section I will point out the customisation options at your disposal by modifying values in the XML. I don't refer to line numbers because these are subject to change if I make alterations to the template XML. It is easy to find where the values that need changing are, however. Task specific settings are under a "TASK SETTINGS" banner which is highly noticeable. There is always the find function in your text editor of choice (usually CTRL+F), use this to search for the property name and this will take you to the section of the XML where the values can be changed.

Under task settings there is a section of code where we tell the application where to find the executable that handles the digit span task. The property name/value keys here are where we can set task-specific properties.

Number of trials

You can select how many trials of each span size you want. The properties to edit here are:

  • 'spanTwoTrials'
  • 'spanThreeTrials'
  • 'spanFourTrials'
  • 'spanFiveTrials'
  • 'spanSixTrials'
  • 'spanSevenTrials'
  • 'spanEightTrials'
  • 'spanNineTrials'
The default values for these properties are "3" for spans 2 through 7 and "0" for spans 8/9. Therefore as it stands the module will administer 3 trials at each list length up to 7 and none at list length 8 or 9. Simply change the integer values within the quotes for each span*Trials property to get the desired number of trials.

Sequential/Randomised trial order

This property decides if the trials are administered in sequential order or not with regards to the list lengths. If sequential then all list length 2 trials are given, followed by all list length 3 trials, and so forth. However, it is often the case that a researcher may wish to administer these trials in a random order so that the participant is not aware on any given trial how many digits they will have to store/recall. The property to edit is:

  • 'randomisedTrials'
The default value is "0" which is the code for sequential order. The alternative is "1" which is the code for random order.

Digit range

Controls the range of digits that the application uses to select digits as stimuli in the trials. The properties to edit are:

  • 'minDigit'
  • 'maxDigit'
The default values are "1" and "99" respectively meaning that any presented digit can range from 1 to 99 (inclusive).

Data Analysis

 

After running the digit span processing script (download from here) you will get a data frame with the following variables. Information on running the script and obtaining the processed data is here

Variable Name Description
fta.score This is the score the participant achieved when the full-trial accuracy scoring method is used.
prop.score The score obtained by the participant when the proportion correct method of scoring is used.
number.successes The score obtained by the participant when the number of correctly recalled elements method of scoring is used.
median.rt The median response time of each digit response (note - not time taken to input whole response to trial).
max.span Maximum list length at which the participant successfully recalled all the elements in the trial.
span.2.corr Number of trials successfully answered (all digits recalled) at list length 2 - "NA" value if there were no trials at this list length administered
span.3.corr Number of trials successfully answered (all digits recalled) at list length 3 - "NA" value if there were no trials at this list length administered
span.4.corr Number of trials successfully answered (all digits recalled) at list length 4 - "NA" value if there were no trials at this list length administered
span.5.corr Number of trials successfully answered (all digits recalled) at list length 5 - "NA" value if there were no trials at this list length administered
span.6.corr Number of trials successfully answered (all digits recalled) at list length 6 - "NA" value if there were no trials at this list length administered
span.7.corr Number of trials successfully answered (all digits recalled) at list length 7 - "NA" value if there were no trials at this list length administered
span.8. corr Number of trials successfully answered (all digits recalled) at list length 8 - "NA" value if there were no trials at this list length administered
span.9.corr Number of trials successfully answered (all digits recalled) at list length 9 - "NA" value if there were no trials at this list length administered
user The value of the username of the account which produced the data