Millisecond Forums

+= is the increment operator. You'll find this and all other available operators covered in the Inquisit documentation's "Operators" topic. Note, however, that one does not even need the increment operator to sum up values across trials. An equivalent way to express

values.sumresponses+=values.response

using just basic addition would be

values.sumresponses=values.sumresponses+values.response

Increment and decrement operators merely allow for more concise code.

Wonderful... didn't know about the "+=" function (as in values.sumresponses += values.responses). 

Thanks again!
Stéphane

You need to create another <values> entry and sum up the response across all trials.

<values>
/ response = 0
/ sumresponses = 0
</values>

<block myblock>
/ trials = [1-10=mytrial]
</block>


<trial mytrial>
/ stimulusframes = [1=mytext]
/ validresponse = (32, 37)
/ ontrialend = [if (trial.mytrial.response == 32) values.response=1 else values.response=0;
    values.sumresponses+=values.response; ]
</trial>

<text mytext>
/ items = ("Press D or K. D -> values.response = 1; K -> values.response = 0")
</text>

<data>
/ columns = [trialnum trialcode response latency values.response values.sumresponses]
</data>