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We are nearing the end of term and most of our undergraduate students will soon be heading home. But we will have studies running throughout the summer, so if you are staying in Egham and would like to take part, do get in touch.

PS We should probably clarify that our research doesn’t actually involve any ice cream. Sorry!

Image: nuchylee / FreeDigitalPhotos.net

If you’re interested, please do get in touch for more information or to arrange a time to come and take part.

So, without further ado…

Trick 1: Context Attributes

In many situations, it can be very useful to be able to set attributes at the top of an application or experiment. By defining a setting at the top (for example, the filename of a sound file that will be played multiple times during the experiment), and then referring to it by its attribute name throughout the experiment, it becomes very straightforward to swap that sound file for another at a later date: rather than having to comb through the experiment looking for everywhere that it might have been referenced, we can simply change the single context attribute “Sound1Filename” to the name of the new file, and every reference to SoundFile1 will be updated in one go. This not only makes it far more straightforward to modify an experiment, but it also greatly reduces the risk of introducing bugs by accidentally missing a reference that needs changing.

It’s possible to do this in E-Prime by using the E-Basic command “c.setAttrib” in an InLine object. I usually call this object ‘Definitions’, and place it at the very top of the experiment, like so:

You can then define attributes inside it as follows:

c.setAttrib "Sound1Filename", "sounds/sound1left.wav"

The above example would assign the value “sounds/sound1left.wav” to the attribute “Sound1Filename”, which can then be referred to anywhere in the experiment – using E-Prime’s square bracket notation – as [Sound1Filename] :

The uses of setting attributes like this are not limited to setting filenames. It’s also possible to dynamically change text in Text objects, set the correct response key globally, etc. By way of example, here are some examples of context attributes one might use in a dichotic listening-type experiment:

c.setAttrib "Attend", "left"
c.setAttrib "Ignore", "right"
c.setAttrib "Sound1FileName", "sounds/sound1left.wav"
c.setAttrib "Sound1CorrectAnswer", "z"

The first two – “Attend” and “Ignore” – simply fill in text in the instructions throughout the experiment. This allows us to very easily create a reverse-stereo version of the experiment, simply by swapping these two around. Since our instruction Text objects are all written in the form “You will be played a sound in the [Attend] ear…”, this allows us to change all the relevant instructions just by changing these two lines.

The third we have already discussed – it sets the filename of the sound that we’re using, making it easy to swap in a different sound at a later date.

The fourth sets the correct response key to this particular sound – this makes it easier to change the response key and, again, it removes the possibility that if we do change it then we’ll overlook one place where this occurs.

There are almost certainly other uses that the above trick could be put to. I think a good principle to follow is that if something is going to be referred to multiple times throughout the experiment, and if there’s a chance that that thing might need to be changed in future, then it’s worth considering setting it as a context attribute by the above technique.

If you’re interested in taking part, or would like to know more, please get in touch.