o They focus on how it is that we build internal representation of objects during the process of recognition. • Pattern Recognition: The ability to recognize an event as an instance of a particular category of event. • Percept: Meaningful interpretation of sensory information. • Recognizing a configuration involves contact between the emerging percept and memory. • Memory Trace: The trace that an experience leaves in the brain. • To recognize a letter “a,” your emerging perception of “a” must make contact with the memory trace of “a.” o This process is called the Hoffding function : When an experience makes contact with a memory trace, resulting in recognition. Template Matching • Template: A model against which a stimulus is compared to determine whether it belongs to a particular category. • Prototype: A model that possesses all the typical characteristics of its class. • Template matching theory: Comparing a stimulus with templates; when they match, the stimulus is recognized as belonging to that category. o Problem: How to specify a template can match not only patterns that are identical to it, but also patterns that are similar enough to it. • Multiple-trace memory model - Hintzman: Traces of each individual experience are recorded in memory. No matter how often a particular kind of event is experienced, a memory trace of the event is recorded each time. o This approach distinguishes between primary and secondary memory: Primary: what we experience at any point in time. Secondary: all the memory traces created out of all the experiences we’ve had. • Secondary memory can be activated by a probe from primary memory. o When a probe goes out from primary to secondary memory, then memory traces are activated to the extent that they are similar to the probe. o The activated memory traces return an echo to primary memory. o The echo is made up of contributions from all the activated memory traces. • Experiment with prototypical patterns showed that: o Prototypical patterns were quite well classified, even though they had never been seen before. o Sometimes participants falsely recognized the prototype as a pattern they had seen before, even though they had previously only seen distortions of the prototype. • Hintzman’s explanations for these results:
o Memory traces of the set of distorted patterns produce an echo which contains what the different distortions have in common and that’s how the prototype is recognized. • Once an echo has been experienced in primary memory, it can leave a memory trace of itself in secondary memory. Feature Detection • Feature Detection Theory – Selfridge: o Detecting patterns on the basis of their individual features. • Pandemonium : A model of pattern recognition consisting of three levels: data, cognitive demons, and decision demons! o Data level: features such as size, color, shape… o Cognitive demons: Feature detectors that decide whether the stimulus matches its pattern.
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- Spring '09