WHO:	Wei Ji Ma , California Institute of Technology
TOPIC:	Manipulation of uncertainty: Multisensory perception and visual short-term memory
ABSTRACT:	We will discuss two examples of how the brain can manipulate uncertainty in processing brief stimuli. 1. When a 10 ms flash is presented along with two 10 ms beeps, observers often report seeing two flashes. This illusion is a consequence of the way the brain combines sensory information. When a bisensory task requires observers to report a single percept, the content of this percept has been shown to be determined by a maximum-likelihood rule. In the flash-beep paradigm, we asked for both a visual and an auditory report. A Bayesian model can then account for the full range of responses, from complete fusion via cross-modal modulation to complete segregation. 2. Visual short-term memory is commonly modelled as a box which can hold about four items reliably, while items which fall outside are subject to guessing. We have conducted a change detection experiment with confidence ratings; this allows to plot receiver-operator characteristics. These do not at all correspond to the predictions of a box model. Instead, a signal detection model can explain the results very well.
WHEN:	1/30/2004 12:00:00 PM
WHERE:	Meliora 269

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