First-order sequential probabilities


New Member
Hi everyone,

This is my first time posting (and English is not my mother tongue), so please excuse any mistakes.

At the moment I am trying to implement an experimental task based on Neely's (1977) Speeded Lexical Decision Task. I am attempting to randomize the trials in each experimental block following the author's procedure, but I do not really understand it.

Neely did the following: "Within and across blocks, the presentation order of the target items was a pseudorandom sequence with the first-order sequential probabilities for condition, target lexicality, and category membership being equated as nearly as possible." (p. 236). I don't know if I have been looking at this too much for too long, but I just can't grasp this idea and am getting increasingly frustrated.

What does the author exactly means by this, how do I obtain these first-order sequential probabilities, and how does this allow me to randomize the trials?

I am very sorry and I know I must appear dumb, but I truly am at a loss.

Thanks in advance!


Active Member
I don't know anything about this test except that I have tried the demo here I assume that this is the sort of thing you are doing.
My best guess is that Neely jumbled the order and then shuffled a bit more if there were any obvious patterns that might distract the subjects. Then thinking that this didn't sound very scientific, wrote the words you quoted. Perhaps I'm a bit cynical. kat