Difference between revisions of "Web-based perception experiments"

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Finally, in (4) above you may have noticed there was reference to a file: process.php.
  
Finally, in (4) above you may have noticed there was reference to a file: process.php.
  +
−
[http://linguistics.berkeley.edu/~kjohnson/talkers/process.php process.php]
  
  +
<?php
  +
  +
$prefix = $_GET["p"];
  +
$n = $_GET["n"];
  +
  +
$datafile = $prefix . "_data" . $n . ".csv";
  +
  +
if ($_SERVER["REQUEST_METHOD"] == "POST") {
  +
$data = "empty";
  +
foreach($_POST as $key=>$value) { // we don't have to know the keys
  +
if ($data == "empty") { $data = $value; }
  +
else {$data = $data . "," . $value;}
  +
}
  +
$data = $data . "\n";
  +
  +
$ret = file_put_contents($datafile,$data,FILE_APPEND| LOCK_EX);
  +
  +
if ($ret) {
  +
echo "saved data";
  +
} else {
  +
echo "there was a problem writing the data";
  +
}
  +
} else {
  +
http_response_code(403);
  +
echo "invalid submission";
  +
}
  +
?>

Revision as of 09:02, 9 February 2018

Experiments can be hosted on the Department of Linguistics server, and then distributed to listeners by email link, or via Amazon Mechanical Turk.

An example is here: example experiment

A Javascript library audexp.js makes it realatively easy to implement the following four typical kinds of experiments:

  • Identification (id) - a single audio file is played, and a two-alternative forced choice (2AFC) is given.
  • Discrimination (ax) - two audio files are played, and a 2AFC is given.
  • Rating (r) - a single audio file is played, and a rating number (from 1 to 7) is given.
  • Contrast Rating (cr) - two audio files are played, and a rating number is given.


Your html code must have four features:

  • (1) after loading audexp.js, load a javascript file that defines
    • an array (or two arrays) of filenames that will be presented.
    • a variable called 'block'
    • here's an example of such a file
    • this .js file was created with a small perl script from a .csv spreadsheet.
    • the html header contains these two lines to get the audexp.js library and the experiment-specific list of sound files.
 <script src="js/audexp.js"></script>
 <script src="js/blocktest_list.js"></script>
  • (2) a call to load the experiment when the page is loaded
    • this call specifies the type of experiment (in this case 'id')
    • whether to randomize the order of presentation of the list of sound files
    • the interstimulus interval for 'ax' and 'cr' types
    • and the intertrial interval for all experiments.


 <body onload="load('id',false,500,2000);">
  • (3) Three or for <span...> elements that will be used to give feedback to listeners.
<span id="wr"></span>  is used to show warnings
<span id="f1">sound 1</span>  is used to indicate that an audio file is playing 
<span id="f2">sound 2</span>  is used to indicate that an audio file is playing 
<span id="key">#</span> is used to indicate which key the listener pressed
  • (4) A <form ...> element named "dataform"
    • the order of the input items determines the column order in the output file>
<form method="POST" id="dataform" action="process.php?p=id&n=1">
     <input type="hidden" name="subject" value=<?php echo $subj; ?> />
     <input type="hidden" name="trial" />
     <input type="hidden" name="list" />
     <input type="hidden" name="file1" />
     <input type="hidden" name="filedur" />
     <input type="hidden" name="mystatus" />
     <input type="hidden" name="loadtime" />
     <input type="hidden" name="response" />
     <input type="hidden" name="rt" />
</form>


Finally, in (4) above you may have noticed there was reference to a file: process.php. 

<?php

$prefix = $_GET["p"];
$n = $_GET["n"];

$datafile = $prefix . "_data" . $n . ".csv";

if ($_SERVER["REQUEST_METHOD"] == "POST") {
  $data = "empty";
  foreach($_POST as $key=>$value) {      // we don't have to know the keys
      if ($data == "empty") { $data = $value; }
      else {$data = $data . "," . $value;}
  }
  $data = $data . "\n";

  $ret = file_put_contents($datafile,$data,FILE_APPEND| LOCK_EX);

  if ($ret) {
     echo "saved data";
  } else {
     echo "there was a problem writing the data";
  } 
} else {
 http_response_code(403);
 echo "invalid submission";
}
?>
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