From jan.derrfuss at nottingham.ac.uk Mon Jul 4 10:16:56 2016 From: jan.derrfuss at nottingham.ac.uk (Jan Derrfuss) Date: Mon, 4 Jul 2016 10:16:56 +0100 Subject: [psychology-visionlist] Psychophysics question Message-ID: Dear all, I was wondering if someone might be able to help me with a psychophysics question. I would like to run an fMRI experiment involving a motion and a colour task. The exact design is still an open question, but I imagine something along the following lines: Stimuli would consist of moving grey dots and stationary coloured dots. In one set of blocks, participants would be instructed to attend to the moving dots. The task would be to detect occasional changes in the movement speed. In the other blocks, participants would be instructed to attend to the coloured dots. The task would be to detect occasional changes in the colour. I would like to have an easy (e.g., 90% of changes detected) and a difficult condition (e.g., 50% of changes detected), and I would like these values to be as similar as possible for the motion and the colour task and across participants. So far, so good. Now, I suspect there would be little point in doing the threshold adjustment outside the scanner (as I would not expect a threshold identified on a monitor outside the scanner to carry over to the projection screen used inside the scanner). In the scanner, however, time is money, and even if I ran a thresholding procedure during the anatomical scans, there would likely not be more than 10 minutes available. My question: Do I stand any chance of achieving what I would like within 10 minutes or so? Any input would be very much appreciated. Cheers, Jan -- _____________________________________ Dr. Jan Derrfuss School of Psychology University of Nottingham University Park Nottingham NG7 2RD Email: jan.derrfuss at nottingham.ac.uk Phone: +44-115-84 67920 _____________________________________