Pattern Recognition (cont.)

1. Pattern Recognition (cont.)

2. Auditory pattern recognition • Stimuli for audition is alternating patterns of high and low air pressure called sound waves • The bigger the difference between high and low pressure the louder the sound is perceived to be • The number of cycles per second determines tone • Humans can hear sounds as low as 20 cycles/sec and as high as 20,00o cycles/sec • Other animals have a greater range of hearing, but humans discriminate between sounds and interpret sound better and more quickly • Speakers produce a continuous string of speech sounds that listeners easily break into separate words

3. Echoic or auditory sensory memory • Similar to visual sensory memory in many ways • Definition – brief memory system that receives auditory stimuli and preserves them for some amount of time • Since hearing is temporal event, you would not be able to understand auditory information if it disappeared immediately

4. Experiments demonstrating echoic memory • 3 eared man study • 3 auditory stimuli (letters or numbers) presented to the left ear, 3 stimuli to the right ear, and 3 stimuli to both ears • Subjects immediatelyasked to report all the stimuli they could remember hearing • Reported about 4 of the 9 • Presented with stimuli again and asked either what were the 1st, 2nd or 3rd stimuli you heard – partial report • Subjects more accurate, over 5 recalled, but not as accurate as Sperling’s measure of visual sensory memory covered last week though echoic memory seemed to last longer

5. Does echoic memory fade? • Subjects presented with a list of 9 numbers, 2 numbers per second • Silent vocalization group read the numbers; a purely visual presentation • Active vocalization group – read the numbers out loud as they were presented • Passive vocalization group- read the numbers and listened to a tape recording of someone reading the numbers

6. Results • Subjects in all groups remembered about 20% of numbers in the beginning of the list and about 50% in the middle of the list • The passive and active vocalization groups remembered 90% of the last item while the nonvocalization group remembered 50% • Suggests that the vocalization groups’ recall was assisted by a still present memory trace in echoic memory • Echoic memory traces do persist over time, but as indicated by decreased memory for early items, the memory trace fades over extended time

7. Does erasure occur in echoic memory? • Backward masking seemed to “erase” meory in visual sensory memory • Previous experiment run again. This time after hearing the list, vocalization groups heard eith a tone or the word “zero” • Told this was a cue to begin recall, actually used to see if hearing another word would erase the memory of the last item • Group that heard the tone performed the same as before. Group that heard zero decreased accuracy to 50% same as nonvocaliztion group • Conclusion: memory of last item was erased. • Overall conclusion: echoic memory similar to visual sensory memory, but has a samller capacity and a longer duration

8. Theories of Auditory pattern recognition • Largely studied in speech, but some work has been done with music • Template theory – we store models or templates of sounds, an then compare sounds we hear to sounds we have stored in memory. • Doesn’t work any better than it did in visual sensory memory. • Speech sounds do not always sound the same though we perceive them as being the same

9. Feature detection theory • We detect basic features of the sound and use memory to identify them – much more successful • Clearly shows the importance of context • Phonetic restoration effect – when a speech sound is missing or covered with white noise, we fill it in and don’t notice it missing • Words are more easily recognized when parts are missing if they are in sentences than as isolated words

10. Haptic pattern recognition • Use of somatosensory system • When blindfolded, most people can identify objects quickly and accurately using haptic (active touch) information • Exploration of an object with hands does not involve random movements

11. Object recognition using haptic information • Begins with enclosing smal object n fingers and palm • Then different kinds of stereotypical hand movements called exploratory procedures

12. Exploratory procedures • A lateral motion to determine texture. • Enclosure to determine global shape and size • Unsupported holding to determine weight • Conture following tto determine exact shape • Applying pressure to determine hardness • Static contact to determine temperature and others

13. Examples • People reported that shape was most important in identifying a pencil • Shape and texture important in identifying a crayon • Shape and size important in identifying a used pencil

14. Visual and haptic information • Vision not necessary for these exploratory procedures to develop. • Visual and haptic objective recognition processes need to work together • Using haptic information to identify objects of different shapes that are the same texture is slow and difficult • Visually sorting objects that identical in shape but differ in temperature or hardness is difficult if not impossible