Visual search Task

noob768

Hi all,

I am new to Opensesame. I am trying to design a visual search task. For the task, the screen is divided into 6*5 and the stimuli can appear in any of the 30 locations (each coordinate from one of the four quadrants). I manually calculated all the coordinates and have been trying to design the experiment. The task has different set sizes (currently I have made only 4 & 8). When the set size was just 4, the experiment was running smoothly. However, when I added trials with set size 8, the experiment is not working. What would be the problem? Can someone help me rectify the issues.

When i am trying to run the experiment, I am getting the following error:

The experiment did not finish normally for the following reason:

• x should be int or float, not

Thankyou

visual search.osexp

Fab

Hi @noob768,

I believe that the problem is that you're trying to draw things that you have not specified.

Here's what you are drawing in your sketcphad, for every trial:

8 objects in total, pulling information from the loop. Yet in your loop, half of the trials contain no information for half of these objects (and, in trials of set size 8, it's actually also missing for the 8th object).

As a result, your sketcphad cannot be prepared.

Hope this helps,

Fabrice.

noob768

Hi,

Thank you for the information. When I incorporated some filler trials, it started working. However, is there a better way to design the whole experiment?

Fab

Hi @noob768,

That depends on your design and what you're trying to achieve.

The simplest way to fix the issue you posted earlier is to include details for all stimuli in your loop but to either use a jpeg that simply consists of a picture filled with the same color as your sketchpad background or to set its coordintes to a location outside the screen. An alternative way would be to use a sketchpad for each set size and use the "Run if" property in the sequence to condition the presentation of each of these sketchpads to the set size.

Best,

Fabrice.

noob768

Hi,

I have done the first option that you mentioned.

I want to randomly present these trials, and so will "run if" function work? I am not sure about that.

Thanks

eduard

Hi Noob,

How about you try it? You can simply check whether run if works fine by trying it out.

However, is there a better way to design the whole experiment?

Yes, there is, but it requires Python programming. You don't need to manually compute the screen coordinates, but let Opensesame do it for you. Just specify the set size and target position in the loop table, the rest has to be implemented in an inline_script. It is not terribly difficult, but you should understand some Python coding. All the information are in the manual. How about you try to get started yourself, and if you get stuck, report back here so we can help?

Eduard