Introduction

If needed, there is also a regular digit span task on PsyToolkit

The reverse digit span task is a modification of the regular digit span task. The basic idea of this task is this:

  1. A person is presented with a sequence of two digits

  2. The person needs to repeat the sequence in reverse order

  3. If the person can do step 2 correctly, then a longer sequence is presented

  4. This goes on until the person can not longer do the sequence

  5. The longest correct sequence is the person’s reverse digit span

Much has been written about the digit span task. It is discussed what it exactly measures (Jones & Macken, 2015).

About this implementation

The reverse digit span task is a almost a perfect copy of the regular PsyToolkit digit spant task (check there for more details).

Run the demo

Click here to run a demo

Data output file

In PsyToolkit, the data output file is simply a textfile. The save line of the PsyToolkit experiment script determines what is being saved in the data output file. Typically, for each experimental trial, you would have exactly one line in your text file, and each number/word on that line gives you the information you need for your data analysis, such as the condition, response speed, and whether an error was made.

The data output is other than in most experiments. In this experiment, there are multiple lines per trial. The reaction time, exactly digit sequences presented and entered are saved. If you are only interested in the ultimate digit span, you can just look at the second number of the last line.

If you embed this experiment yourself, make sure to set only the following two parameters in the analysis section of your experiment as follows:

  1. Which column has dependent variable? set to value 2

  2. Only include last n lines set to value 1

Make sure not to fill in any of the other parameter boxes. This way, the data analysis will only look at the last line of each experiment data file, which contains the participants' best score. There is much other interesting information in the data files. If you really one, you can download all those files to your own computer and analyze further with your own script. But that is not necessary to take out the digitspan result.

PsyToolkit code

Click to expand the PsyToolkit script code (part of zip file below) 
options
  mouse on
  bitmapdir stimuli
  scale
  
fonts
  normalfont arial 18
  bigfont    arial 28

bitmaps
  digit1 # 1
  digit2 
  digit3
  digit4
  digit5
  digit6
  digit7
  digit8
  digit9
  digit0  # 10
  ##
  continue_button
  continue_button_dark ## for after being clicked
  clear_button
  mask
  # -- instructions ------------
  i1
  i2
  i3
  i4
  backButtonImage
  nextButtonImage
  startButtonImage

## important variables:
## &spancounter : the number of trials WITHIN a span (maximally 3)
## &spancorrect : the number of correct trials WITHIN a span (maximally 2, need 2 to continue)
## &actualspan : the max number someone remembered

######################################################

task digittask ## starts with 2 and then goes up every correct 2
  ## Step 1: Create random number sequence
  set &&allNumbers range 1 10 ## from the bitmaps
  set &&numberSequence sample &testspan from &&allNumbers
  ## Step 2: Start screen with basic instruction to get ready
  font bigfont ## use big font for following two texts
  show text "Memorize digits"  #1
  delay 1000
  clear -1
  show text "Get ready now!" #2
  delay 800
  clear -1
  font normalfont ## back to smaller font for rest of texts
  ## Step 3: show all digits at 800 ms per digit
  set $tmp_counter 1
  while $tmp_counter <= &testspan
    show bitmap &&numberSequence[$tmp_counter] #3
    delay 800 ## how long each to-be-memorized digit will be shown
    clear -1
    set $tmp_counter increase
  while-end
  # 
  # Step 4: show the possible clickable digits and other buttons
  #
  show bitmap continue_button 250  250 
  set $range_begin show-counter 
  show bitmap clear_button -250  250
  set $clear_counter show-counter
  #
  show bitmap digit1  -150 -250
  show bitmap digit2     0 -250
  show bitmap digit3   150 -250
  #		                
  show bitmap digit4  -150 -160
  show bitmap digit5     0 -160
  show bitmap digit6   150 -160
  #		           
  show bitmap digit7  -150 -70
  show bitmap digit8     0 -70
  show bitmap digit9   150 -70
  #
  show bitmap digit0     0  20
  #
  show rectangle 0 100 350 5   255 255 0 ## vertical "line", looks nice
  #
  set $range_end show-counter
  #
  # Step 5: Now let participant click the digit sequence from memory
  #
  set &&mask_stimuli clear ## for keeping track of masks overlayed on stimuli in virtual keyboard
  set &&range_array range $range_begin $range_end ## so that we can later remove already clicked items from it
  set &&digits_chosen clear
  set &&already_done clear
  while $finish_selection == 0 ## loop until continue button clicked
    readmouse l 1 99999 range &&range_array
    set &&clickedStimuli append UNDER_MOUSE ## store for later save
    set &&rts append RT                     ## store for later save
    if UNDER_MOUSE == $range_begin ## continue button was clicked
      set $finish_selection 1
      show bitmap continue_button_dark 250 250 # cover over continue button
      show bitmap continue_button_dark -250 250 # cover over clear button
    fi
    if UNDER_MOUSE == $clear_counter ## clear button clicked
      set $position_counter decrease 1
      set $last_digit &&digits_chosen remove last
      set $tmp &&range_array_removed remove last ## these values were stored
      set &&range_array append $tmp ## increase range array
      ## now remove last mask drawn and last digit underneath
      set $last_mask &&mask_stimuli remove last
      set $last_digit &&digitsUnderStimNums remove last
      clear $last_mask
      clear $last_digit
    fi
    if UNDER_MOUSE > $clear_counter ## a digit button was clicked
      set $position_counter increase
      set &&range_array remove value UNDER_MOUSE ## remove so it cannot be clicked again
      set &&range_array_removed append UNDER_MOUSE ## the removed values need to be saved in case you want to undo this action ("clear")
      set $clicked_stimulus_x getx UNDER_MOUSE
      set $clicked_stimulus_y gety UNDER_MOUSE
      show bitmap mask $clicked_stimulus_x $clicked_stimulus_y  ## mask the digit
      set $tmp_mask show-counter
      set &&mask_stimuli append $tmp_mask ## keep track of the mask stimuli in case removal needed
      ## now show red circle on the digit button that was clicked
      show circle $clicked_stimulus_x $clicked_stimulus_y 20   255 100 100
      delay 100
      clear -1
      ## 
      set $myIndex expression UNDER_MOUSE - $clear_counter ## this makes the digits go from 13 to 22
      ## was this digit clicked before
      set $already_done &&digits_chosen locate $myIndex ## check if digit was already clicked before
      if $already_done == 0 ## if not already clicked (each digit is only used once in sequences)
        set &&digits_chosen append $myIndex
        set $xPosDigits expression $position_counter * 60 - 300
        show bitmap $myIndex $xPosDigits 150
        set &&digitsUnderStimNums append SHOW_COUNTER
      fi
    fi
  while-end
  #
  # Step 6: Save detailed trial data
  #
  save BLOCKNUMBER "clickedStim" &&clickedStimuli
  save BLOCKNUMBER "rts" &&rts
  #
  # Step 7: digit entry done, check if sequence was entered correctly
  # the only difference with regular digitspan is that you need to reverse it here
  set &&reversedSequence &&numberSequence
  set &&reversedSequence reverse
  if &&digits_chosen == &&reversedSequence
    set $error_status 0
    save BLOCKNUMBER &best_so_far &testspan $error_status "//" &&numberSequence "//" &&digits_chosen
    set &spancorrect increase
    show text "CORRECT" 0 70
    if &spancounter < 3
      set &spancounter increase     
    fi
    if &spancorrect == 2
      set &spancounter 0
      set &spanerror 0
      set &spancorrect 0
      set &best_so_far &testspan
      set &testspan increase
    fi
  fi
  if &&digits_chosen != &&reversedSequence
    set $error_status 1
    save BLOCKNUMBER &best_so_far &testspan $error_status "//" &&numberSequence "//" &&digits_chosen
    set &spanerror increase
    if &spancounter < 3
      set &spancounter increase     
    fi
    show text "WRONG" 0 70
  fi
  delay 2000
  set &&clickedStimuli clear
  set &&rts clear
  #
  # end task when 2 errors in row
  #
  if &spanerror == 2
    set &digitspan &testspan
    end tasklist
  fi
  # end task when digitspan is going to 11
  # this is unlikely to happen, though
  if &testspan == 10
    end tasklist
  fi

######################################################################
## blocks
######################################################################

block training
  pager option mouse backButtonImage -240 230 nextButtonImage -30 230 startButtonImage 240 230
  pager i1 i2 i3
  set &testspan 2
  tasklist
    digittask 1
  end

block digit_block
  message i4 mouse
  set &testspan 2
  set &spancorrect 0
  set &spanerror 0
  set &spancounter 0
  tasklist
    digittask 99
  end
  feedback
    text 0 -200 "Your memory score is the sequence you could remember 2x in a row."
    text 0 -100 &best_so_far ; prefix "Your best sequence (digit span): "
    text 0  100 "Click the mouse anywhere to continue"
    wait_for_key mouse
  end

Download

If you have a PsyToolkit account, you can upload the zipfile directly to your PsyToolkit account. Watch a video on how to do that. If you want to upload the zipfile into your PsyToolkit account, make sure the file is not automatically uncompressed (some browsers, especially Mac Safari, by default uncompress zip files). Read here how to easily deal with this.

Further reading