Adding instructions

So far, we just focused on the stimuli, random treatment order and response registration. Now we will add an instruction, so that subjects understand what the task is. An instruction is just another set of text pictures and screen locations to display:

First we define an additional feedback text

PICTURE Title T
Choice Reaction Time Task
PICTURE Inst1 T
You will see the words ‘left’ or ‘right’

Press the corresponding response key

X-key for right

Y-key for left

PICTURE Prompt T
Press a response key to start the task

Now, we need three screen positions for presenting the text. We will reuse the center, but add screen positions for title and prompt

POSITION Top P 0, -50
POSITION Bottom P 0, 40

Now, we are ready to define a trial which is displaying the instruction

TRIAL Instruct
SP Title Top
&SP Inst1 Center
&SP Prompt Bottom
WK ResKeys

Title, text, and prompt are combined into one single display by adding the ‘&’ to the ShowPicture (SP) trial commands. The WK trial command waits for a key press for the keys defined in ‘ResKeys’

Let’s now invest in some nicer text font to make the instruction appear in a larger font size:

FONT Big Arial 10 1 bold
FONT Std Arial 6
FONT Small Arial 4

Font size is defined in mm height. To activate the font we insert SetFont (SF) trial commands before the respective SP command

TRIAL Instruct
SF Big
SP Title Top
SF Std
&SP Inst1 Center
SF Small
&SP Prompt Bottom
WK ResKeys
SF Std

We end the trial with an SF command activating the ‘Std’ font so that our stimuli will be shown in 6mm font size

To present an instruction, we must add an RUNTRIAL command to the Session definition before the actual Block will be executed:

SesSION My First Experiment
RUNTRIAL Instruct ; Execute trial ‘instruct’
RUNBLOCK ChoiceRT 10 ; Execute block ‘ChoiceRT’ with 10 trials in random order

Trials execute with the RUNTRIAL command are not recorded and will not appear in the result file.

For the final script, we are replacing the text elements of the trial by variable arguments to be able to reuse this trial for multiple instruction pages.

FONT Big Arial 10 1 bold
FONT Std Arial 6
FONT Small Arial 4

PICTURE Title T
Choice Reaction Time Task
PICTURE Inst1 T
You will see the words ‘left’ or ‘right’

Press the corresponding response key

X-key for right

Y-key for left

PICTURE Start T
Press a response key to start the task

POSITION Top    P 0,-50
POSITION Bottom P 0,40
POSITION Center P 0,0

KEY ResKeys
X M          ; Define a Key Set consisting of’ ‘X and ‘M’

PICTURE Correct N
PICTURE Wrong    N
PICTURE Late     N

POSITION FBpos P
0,30

TRIAL Instruct
SF Big
SP ? Top
SF Std
&SP ? Center
SF Small
&SP ? Bottom
WK ResKeys
SF Std

PICTURE Left N
PICTURE Right N

TRIAL ShowWord
CS 2000          ; Clear Screen and wait for 1000 ms
RK ResKeys 3000          ; Activate Response Registration with MaxRt = 3000
SP ?     Center 1 0 1          ; Show a variable Picture until response is done or end of MaxRt
FB ?          ; Compare the response against the correct key
    1:SP Wrong   FBpos 1 1000          ; Show ‘Wrong’ for 1s if response is wrong
    2:SP Correct FBpos 1 1000          ; Show ‘Correct’ for 1s if response is correct
    3:SP Late    FBpos 1 1000          ; Show ‘Late’ for 1s if response is correct

BLOCK ChoiceRT 2
1 ShowWord Left   X          ; Run Trial with ‘Left’ as the Picture and X as correct key
1 ShowWord Right M          ; Run Trial with ‘Right’ as the Picture and M as correct key

SesSION My First Experiment
RUNTRIAL Instruct Title Inst1 Start          ; Execute trial ‘instruct’ and insert the pictures as instructions
RUNBLOCK ChoiceRT 10           ; Execute block ‘ChoiceRT’ with 10 trials in random order