Millisecond Forums

Multiple separate picture presentation and randomising inter-trial intervals

https://forums.millisecond.com/Topic22749.aspx

By Greeny - 10/29/2017

I have 2 questions regarding presenting pictures with no response requirement: 

1. This it the code I have currently:

<trial Positive_Green_pos_1st>
/stimulustimes = [0=Forward_CS_Green_pos_1st; 4000=US_pos; 8000=Backward_CS_Green_pos_1st]
/timeout = 12000
/posttrialpause = 5000
</trial>

I want Forward_CS_Green to show for 4 seconds, then for it to disappear and for US_pos to show for 4 seconds, then for it to disappear and Backward_CS_green to appear for 4 seconds (picture offset coinciding with picture onset). When I run the trial above, the Forward_CS appears then disappears as the US_pos appears, but then the US_pos stays on the screen while the Backward_CS appears and they both disappear together. How do I stop the US_pos from remaining on the screen at the onset of the Backward_CS?

2. I would like to present 3 different inter-trial intervals - 5, 7, and 9s. Is there a way to do this?

I tried:

/posttrialpause = 5000; 7000; 9000 - but it only presented the 9s pause - is there a way to make Inquisit present these 3 different pauses randomly?

Thanks,
Luke
By Dave - 10/30/2017

Greeny - Sunday, October 29, 2017
I have 2 questions regarding presenting pictures with no response requirement: 

1. This it the code I have currently:

<trial Positive_Green_pos_1st>
/stimulustimes = [0=Forward_CS_Green_pos_1st; 4000=US_pos; 8000=Backward_CS_Green_pos_1st]
/timeout = 12000
/posttrialpause = 5000
</trial>

I want Forward_CS_Green to show for 4 seconds, then for it to disappear and for US_pos to show for 4 seconds, then for it to disappear and Backward_CS_green to appear for 4 seconds (picture offset coinciding with picture onset). When I run the trial above, the Forward_CS appears then disappears as the US_pos appears, but then the US_pos stays on the screen while the Backward_CS appears and they both disappear together. How do I stop the US_pos from remaining on the screen at the onset of the Backward_CS?

2. I would like to present 3 different inter-trial intervals - 5, 7, and 9s. Is there a way to do this?

I tried:

/posttrialpause = 5000; 7000; 9000 - but it only presented the 9s pause - is there a way to make Inquisit present these 3 different pauses randomly?

Thanks,
Luke

Re. #1 see https://www.millisecond.com/support/docs/v4/html/howto/howtoerase.htm
In short, you need to define a <shape> that overwrites / covers up any previously displayed stimuli and display that shape at the desired points in time via your /stimulustimes:

/stimulustimes = [0=eraser, Forward_CS_Green_pos_1st; 4000=eraser, US_pos; 8000=eraser, Backward_CS_Green_pos_1st]

with

<shape eraser>
/ shape = rectangle
/ size = (100%, 100%)
/ erase = false
...
</shape>

Re. #2: Use an expression for the random posttrialpause:

<expressions>
/ randposttrialpause = replace(5000, 7000, 9000)
</expressions>

with

/ postrialpause = expressions.randposttrialpause
By Greeny - 10/30/2017

Excellent - thanks Dave :D