Trial duration conditioning on the type of image

[wangzhuoranivy]

Hi everyone,

I am new with JsPsych and I have a problem with adjusting image duration based on what kind of image it is. I have two types of images: cats and person faces and I would like the cat images to last 200ms and person face images to last 700ms. However, I tried to use this.stimulus and it did not work. Could anyone help me out with this?

Thanks a lot,

Ivy

// display image
	var pic_scr = {
		type: 'image-keyboard-response',
		stimulus: jsPsych.timelineVariable('face'),
		data: {screen: 'picture'},
		trial_duration: function () {
                        if (this.stimulus == 'img/Cat_1.jpg' || 'img/Cat_2.jpg' || 'img/Cat_3.jpg') {
				return 200;
			} else {
				return 700;
			}
                },
		response_ends_trial: false
	};

// determine the trial sequence
	var VMRT_task = {
                timeline: [focus_pt, pic_scr, blank1_scr],
	        timeline_variables: [
			{face:'img/Cat_1.jpg'},
			{face:'img/Cat_2.jpg'},
                        {face: 'img/Cat_3.jpg'},
                        {face: 'img/Face_1.bmp'},
                        {face: 'img/Face_2.bmp'},
			{face:'img/Face_3.bmp'}
		],
	        // specify the randomization conditions
	        sample: {
			type: 'with-replacement',
			size: 5,
		}
    };

[vijaymarupudi]

Try something like this. The second parameter of timelineVariable() should be true when used in a function.

// display image
var pic_scr = {
  type: "image-keyboard-response",
  stimulus: jsPsych.timelineVariable("face"),
  data: { screen: "picture" },
  trial_duration: function() {
    const imagePath = jsPsych.timelineVariable('face', true)
    if (imagePath.includes('Cat')) {
      return 200
    } else {
      return 700;
    }
  },
  response_ends_trial: false
};

// determine the trial sequence
var VMRT_task = {
  timeline: [focus_pt, pic_scr, blank1_scr],
  timeline_variables: [
    { face: "img/Cat_1.jpg" },
    { face: "img/Cat_2.jpg" },
    { face: "img/Cat_3.jpg" },
    { face: "img/Face_1.bmp" },
    { face: "img/Face_2.bmp" },
    { face: "img/Face_3.bmp" }
  ],
  // specify the randomization conditions
  sample: {
    type: "with-replacement",
    size: 5
  }
};

[wangzhuoranivy]

I just tried this and it worked. Thank you so much for your help!