Millisecond Forums

White screen on Mac during BIRD task

https://forums.millisecond.com/Topic19475.aspx

By ramzadragoon - 8/3/2016

Hello,

One participant in our study reported that, after completing a survey and progressing to the BIRD task on their Mac computer, their screen went white and they were unable to complete the task. Furthermore, they pressed Ctrl+Q which skipped not only the BIRD task but also the final task, and routed them to the website they should be sent to after the battery has been completed. They tried to do this 3 times unsuccessfully.

I am unfamiliar with Macs, so I do not know what a white screen means in terms of errors, and I do not have access to participant crash logs or system specs. Could it be a sound card issue, as the BIRD is the only task that requires sound? Other participants have completed the tasks without problem on Macs.

Here is my batch code:
<batch CSRPIB2>
/file = "Staics.iqx"
/file = "BIRDrev.iqx"
/file = "DotProbe.iqx"
</batch>

The BIRD is virtually unchanged from the test library, although I added code to prevent spam-clicking and changed the block durations, which has worked on every other device so far.

The participant also completed another battery with a Go/No-Go task successful, so I don't think it is a video card issue, as the Go/No-Go task we used is image-intensive.

Please let me know if you have any ideas - the participant's sibling will be completing the same battery on the same computer, so it would be great if we could get these tasks working again. Thank you!
By Dave - 8/4/2016

I don't think that the <batch> syntax is the issue here. I'd recommend you check the web logs for the respective participant: Those are available via your millisecond.com account.

A white screen in and of itself does not indicate any specific error. and given that (as you say) things work fine for other participants (including those using Macs), I don't think there is anything wrong with the script(s) either. It may well be that the participant's Mac has some kind of particular issue which prevents the script from working properly; whether that is related to the script using sounds or not is impossible to say without further details.

I'd be happy to take a closer look at your experiment, but you would have to provide the link to its launch page.
By ramzadragoon - 8/5/2016

Hi Dave,

Thank you for looking into this. I looked at the web logs and no error messages were reported for that participant - the script must not have crashed. Maybe it is just some kind of display issue on that participant's computer - or possibly stemming from their use of Safari 6, which we have not tested the experiments with.

In any case, here is the launch page: http://research.millisecond.com/jrb513/CSRPIBattery2.web
By Dave - 8/5/2016

Thanks for providing the link to the launch page. I've looked the scripts over and ran some tests, and I have been unable to spot any problems that would explain the "white screen" issue experienced by your participant. I don't think the browser used (Safari) would make a difference. Inquisit Web does not technically run "in" your browser -- the browser is merely the delivery channel for the Inquisit "engine" (the code that actually executes a script on your computer), the scripts and their associated files (images, etc.). The engine, however, comes packaged in a number of different ways to accommodate for different systems' and/or browsers' features, e.g. packaged as a Java application, as a browser "plugin", or as a browser-independent executable (the "Web Player").

If the participant in question, for example, used the Java method (the web log entries will tell your what variant of the engine was used), it may be worthwhile to have her/him try a different launch method (via the "Having trouble starting?" link on the launch page). Trying a different browser would have a similar effect in many cases, because not all browsers support the same launch methods (for example, under Chrome only the Web Player would be available, because Chrome no longer supports certain types of plugins, which rules out Java and the Inquisit Web NPAPI plugin).

Finally, based on the reported "white screen", it *could* be that the respective script somehow got corrupted  when it was downloaded to the participant's computer. A white screen is what you would see when trying to run a script that basically does nothing, i.e., has no proper <expt>, <block>'s, <trials> and stimuli defined. Admittedly, though, this is pure speculation on my part. The chances of this happening are extremely low. If it is the case, however, then clearing the system's browser cache and temporary files prior to trying to start the experiment again should lead to "fresh" copies of the files being downloaded.

Hope this helps.
By ramzadragoon - 8/8/2016

Really appreciate it, Dave! I will try some of these recommendations out.
By ramzadragoon - 8/11/2016

No luck, unfortunately - the same white screen appeared. It must be an anomalous hardware error or something. Thank you for responding!