How to record two simultaneous key responses? (using Psychtoolbox)

In my experiment design, a pair of participants should press different keys (one should press 'z', the other should press '/' on the same keyboard) to respond to the signal appearing on the same screen. But I want to know how to record two different key responses with very short time intevals.

Hope I can get some advice on how to fix the code below:

while true
            [~,~,keyCode]=KbCheck;
            if keyCode(KbName('z'))
                endtime1=GetSecs
            end
 end
 while true
            [~,~,keyCode]=KbCheck;
            if keyCode(KbName('/'))
                endtime2=GetSecs
            end
            i=i+1;
            break;
 end

[Walter Roberson]

what if the / is pressed first ? the second person might not realize you are waiting for them to press it again

[SOJIN YU]

Thank you for your suggestion! I might not have been too clear explainning my question. The two participants are using the same keyboard, and they know that they are required to press the two corresponding keys at the same time. However, the problem for me right now is that I do not know how to record two key responses given at the same time. Do you have any sugguestions? Thank you in advance!

[Walter Roberson]

in any experiment in which people are expected to do something at the same time then either person might perform the action first. Your code outline discards all inputs until it sees one particular one and then discards all inputs until it sees the other. If the second person types first your code outline would discard it because it discards everything until it sees the character expected for the first .

Answer 1

[Walter Roberson]

  gotem = false(1,2)
  times = zeroes(1,2)
  while ~all(gotem)
     get a key
     [tf,idx] = ismember(the key, appropriate values )
    if tf 
       gotem(idx) = true
       times(idx) = GetSecs
   end
   end

Note that in this code if the same key is pressed multiple times then the last is recorded . Recording the first instead would be easy

[SOJIN YU]

Thank you very much! It helped me a lot:)!!