negative RTs?

SuperLab SuperLab 4 Support
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1

Hello,

I have designed a cross-modal probe recognition study. My problem is, about 1/6 of my RTs are negative, and I don’t seem to understand why.

My trials consist in the following events:

  • preCue (a “+” sign), presented until the participant presses a button (RT not recorded)
  • Cue (another “+” sign), presented for 200 ms
  • audio file, event to end “immediately after the event is presented”
  • inter-stimulus interval (blank screen), presented for 1000 ms (RT non recorded, RT timer reset)
  • probe (text, yes/no answer), presented until a response from the participant (RT recorded, RT timer reset)

The only recorded RT I am interested in is the last one, they are the only recorded. I exclude the participants are just answering before they see the probe, because accuracy is very high (>90%)

Has anyone else had this problem? Do you have any suggestions about what might be causing it?

Thanks!

2

Can you post a sample data file?

3

Here’s an example:

Participant Group Participant Name Block Name Trial Name Event Name Cumulative Time Participant Response Key Pressed or released Error Code Reaction Time
GroupB3 OlS_B3_500 BlockB3 Filler49 PF49 156899 Red key (no) 2 Pressed C 1578 filler filler
GroupB3 OlS_B3_500 BlockB3 Filler50 PF50 164482 Green key (yes) 4 Pressed C 94 filler filler
GroupB3 OlS_B3_500 BlockB3 Filler51 PF51 174672 Green key (yes) 4 Pressed C -373 filler filler
GroupB3 OlS_B3_500 BlockB3 Filler52 PF52 180271 Green key (yes) 4 Pressed C 1215 filler filler
GroupB3 OlS_B3_500 BlockB3 85_12b_low P_12b 187806 Red key (no) 2 Pressed C -67 test low
GroupB3 OlS_B3_500 BlockB3 Filler53 PF53 193197 Green key (yes) 4 Pressed C 1030 filler filler
GroupB3 OlS_B3_500 BlockB3 87_02b_high P_02b 197180 Red key (no) 2 Pressed C 1171 test high
GroupB3 OlS_B3_500 BlockB3 Filler54 PF54 204539 Green key (yes) 4 Pressed C -1658 filler filler
GroupB3 OlS_B3_500 BlockB3 Filler55 PF55 214217 Green key (yes) 4 Pressed C 1305 filler filler
GroupB3 OlS_B3_500 BlockB3 90_07b_high P_07b 220759 Red key (no) 2 Pressed C -1339 test high
GroupB3 OlS_B3_500 BlockB3 Filler56 PF56 232517 Green key (yes) 4 Pressed C 1199 filler filler

4

apparently there are negative RTs showing up also in my self-paced reading experiment. How is this possible? Please find attached the two scripts plus two sample data obtained with them.

Any help with this would be greatly appreciated!

probeDE_audio.sl4 (145 KB)

probeDE_data.txt (12 KB)

selfpacedDE.sl4 (228 KB)

selfpacedDE.txt (15.1 KB)

5

an update: both these scripts seem to work on my Mac laptop (no negative RTs there). So I guess this does not have anything to do with the response pad or with the scripts themselves, but it must be a problem of the Win machine. Any suggestions wrt what it may be?

6

Can you tell me what operating system you are using on Windows (XP, Windows 7 - 64 bit, Vista)? Also, what version of SuperLab do you have? You can find this within then Help menu and then choosing About SuperLab. The most current version is 4.5.4.

7

I am using Superlab 4.5.3, and WIndows XP Professional Service Pack 3 version 2002
on an AMD Athlon 64 X2 Dual Core Processor 4600+ (2.39 GHz, 1,87 GB of RAM)

Thanks!

8

Thank you for contacting us directly regarding this matter.