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 1 st, 2 nd or 3 rd 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