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Builder textbook errata



Hi all,

I’ve just started working my way through the Building Experiments in PsychoPy textbook. In Chapter 3 where it walks through creating the Glasgow Face Matching Task (GMFT) I think there may be an error, but because I’m new to this it seems more likely I’ve misunderstood.

When an image is placed onto the screen, the orientation of the image references a variable called $ori. The conditions file that lists all the trials doesn’t have such a variable in the book or from the online resource for this book. When I try to run the experiment it understandably complains that the variable doesn’t exist.

Can any confirm that I should revert back to whatever it was as default, or am I missing something?



The issue arises on page 47, but on page 51 it becomes clear that $ori is a variable that can be defined to start tweaking things. It just means that in Figure 3.2 on p47 you should leave orientation as just “0” and “constant” until you get to p51



Thanks for pointing this out. Please let us know of any other problems you might encounter in your detailed reading.


I could be wrong, but I think in Chp 2 there’s mention of adding a fixation cross into the ITI, and I think that also gets referenced later in Chp 4 as something that’s already been done. Chp 4 is where a fixation cross is first explained. I might be misremembering though! Thanks for your quick reply


Well if sales are good enough, there might even be a second edition where we can incorporate this sort of feedback :wink:


Maybe we need a new errata thread. Fig 5.2 shows the Basic tab, but in text is being used to demonstrate something under the Advanced tab