Millisecond Forums

Hi all!

I am creating a simple experiment where participants see a picture of an object, followed by a sound, and must respond with two simultaneous key presses. When participants respond, it should immediately go on to the next trial. The following code does that, which is great. However, I would like it so that pressing just ONE key (either 34 or 38) is recorded as an incorrect response. Currently, pressing just one key does nothing and Inquisit waits for a second key press before moving onto the next trial. 

I am assuming the problem lies somewhere in the <trial> element (see below). Anyone have any ideas? 

Thank you all in advance :-)


<trial power_low>
/ inputdevice = keyboard
/ ontrialbegin = [list.bigstims.nextvalue]
/ ontrialbegin = [values.Grip = "WHG"; values.Tone = "low"]
/ ontrialbegin = [values.first_key=0; values.first_key_latency=0;
  values.second_key=0; values.second_key_latency = 0;
  values.correctkeys = "34, 38"; ]
/ stimulustimes = [1 = big_objects; 2000 = sound.low]
/ validresponse = (34, 38)
/ isvalidresponse = [if(values.first_key==0) {
  values.first_key=trial.power_low.response;
  values.first_key_latency=trial.power_low.latency;
  false; };
  if (values.first_key != 0 && trial.power_low.latency>values.first_key_latency) {
  values.second_key=trial.power_low.response;
  values.second_key_latency = trial.power_low.latency;
  false; };
  values.first_key != 0 && values.second_key != 0]
/ iscorrectresponse = [contains(values.correctkeys, values.first_key) && contains(values.correctkeys, values.second_key)
                        && (values.first_key != values.second_key)]
/ beginresponsetime = 2000
/ responseinterrupt = immediate
/ recorddata = true
/ timeout = (7000)
/ branch = [if (trial.power_low.error) trial.errorfb]
/ branch = [if (trial.power_low.correct) trial.correctfb]
</trial>