Inferential tools for visual cognition

Problem 1 - Visual search What conclusions might I be able to draw from the msec. data summarised below? What other data do I need to really make sense of these results?

Problem 2 - Same/different visual imagery task What conclusions can I draw from the % accuracy data summarised below?

Neurophysiology Single cell recording Brain imaging (fMRI, PET)

What kinds of neurophysiological questions does it make sense to ask? What cells respond to specific stimulus properties? How selective are the responses of cells? How are networks of cells organised? What brain regions process specific information? How are networks of brain regions interconnected?

Neuropsychology Dissociation Double dissociation

What neuropsychological questions does it make sense to ask? Damage to which areas leads to what deficits? Which processes are functionally independent of each other?

Psychophysics Measures of sensitivity Thresholds (e.g. method of limits) Signal detection theory (ROC curves)

Determination of lower limit of audible pitch, (Titchener, 1910)

What psychophysical questions does it make sense to ask? What is the detection threshold for a stimulus under specific conditions? How sensitive are observers to specific parametric manipulations?

Behavioural measures Introspection Reaction times (Mental chronometry) Errors

Reaction times: Transduction of physical energy into neural code + Transit time to brain area (areas) where decision can be made + Decision processing time + Transmission of decision to muscles for action + Muscles to complete response

Decisions: Relevant stimulus processing Strategic response concerns (time pressure, accuracy, etc)

What questions does it make sense to ask from behavioural measures? How do task factors affect response times/error rates? How do strategic factors affect response times/error rates?

Cognitive psychology Careful consideration of representations and processes underlying behaviour. No assumptions regarding brain-behaviour relationships.

What kinds of questions does it make sense to ask in cognitive psychology? What predictions can be made from models to behavioural measures? Do the effects found in the behavioural measures match those predicted by the models.

The relationship between models and data can be formalised as: Q. What happens when prediction from model is not supported by the observed data?

How can cognitive models be used. As coherent explanations of mental life in their own right. As inferential tools for neurophysiological, neuranatomical, neuropsychological and psychophysical approaches. Given a particular hypothesis concerning the relationship between behaviour and brain, a specific model might imply the existence of particular neural modules.