How to apply a mask (disappearing stimuli) in OpenSesame

alepc

Hi everyone,

I am a new user on OpenSesame. I need help figuring how to apply a mask in the sketchpad.

I found this tutorial but it doesn't help because I can't seem to find the mask icon that they refer to. https://osdoc.cogsci.nl/2.8.3/tutorials/aps-tutorial/#step-4-design-the-fixation-target-and-mask-sketchpads

What I want to do is show a word and shape for 2000ms and after the first 250ms I want the shape to disappear and the word to remain. I was hoping to accomplish this by adding a mask so that I can record when participants press any key.

Please help. Any and all feedback is greatly appreciated.

Fab

Hi @alepc,

Welcome to the forum!

You would need to provide more information for other users to be able to possibly help. When are you expecting participants to respond? How are the shape and word presented? Do they overlap? Are they presented as separate objects or are you using a single picture combining both?

The tutorial you refer to contains no "mask icon". It simply is a sketchpad used to present the mask. There is no "mask" object per se in Open Sesame

In your task, if responses take longer than 250ms, I don't think you actually need a mask. You can show a first sketchpad with both objects (word and shape) for 250ms, then show a second sketchpad with the word for 0ms followed by a keyboard object with a timeout duration of 1750ms. RTs would then be measured from that second sketchpad (so if you want to measure it from the first, you'd just have to add to the RT variable the duration of the first sketchpad (250ms).

If you want participants to be able to respond during the first 250ms, or if you want to word to remain on the screen for 2000ms even if participants respond earlier, it gets more complicated and you'd have to do some programming (a method for continuous trials can be found here: https://forum.cogsci.nl/discussion/7063/register-response-with-continuous-trial#latest). The programming language would depend on whether you plan to use Open Sesame or OSWeb (in the latter case, you must use Javascript). Alternatively, if you plan to run Open Sesame in the lab (not OSWeb), you may want to explore the option of coroutines (https://osdoc.cogsci.nl/3.3/manual/structure/coroutines/).

Good luck!

Fabrice.