Summary

The aim of this tutorial was to investigate the application of psychophysical methods to measure perceptual sensitivity.

We began by introducing a visual stimulus and task of interest (motion), and suggested a simple method of evaluating sensitivity to motion. We then realised that this method was subject to the observer’s bias to respond “yes” or “no”, and discussed how signal detection theory provides a framework for separating sensitivity from bias. We used an example experiment to collect hit and false alarm rates in a global motion detection task, and saw how such information is used to estimate sensitivity (d’). We then considered how the physical stimulus might be translated into an ‘internal response’ via a ‘delay-and-compare’ circuit before investigating an applied perception example that examined differences in facial emotion sensitivity between those with and without a diagnosis of schizophrenia. Finally, we discussed an alternative experimental design (two-alternative forced-choice) that is less susceptible to bias.

You should now have achieved the principal learning outcomes from this tutorial:

  • Explain how motion sensitivity can be measured and describe the importance of considering response bias.
  • Define ‘motion’ and depict and interpret space-time representations.
  • Construct and explain the operation of a ‘delay-and-compare’ motion detection circuit.

Next steps

To indicate your participation in this tutorial, you are required to complete a quiz on Moodle. The quiz is titled ‘“Measuring perception” quiz’, and becomes visible once you have clicked the link to reach this tutorial site. The quiz does not contribute to your mark for this course, but allows you to judge your achievement of the tutorial’s learning outcomes. You are required to have submitted the quiz by 9am Monday of Week 7 (September 3, 2018) to be marked as having attended this tutorial.

We have only just scratched the surface of psychophysics in this tutorial. If you are interested in learning more, you’re welcome to come and chat to any of the vision researchers in the school. Also, you will find some Additional resources in the next section that you might find useful and interesting.