PSY 368 Human Memory Sensory Memory

Structural Model Memory composed of storage structures that hold memories for a period of time Sensory memory Short-term memory (STM) Long-term memory (LTM)

Sensory Memory Sensory memory Very short storage of info from senses Functions: To allow further processing of the info (STM) Helps us to connect our sensory experiences Multiple stores: Visual sensory memory = iconic memory (Neisser, 1967) Auditory sensory memory = echoic memory Touch sensory memory = haptic memory

The eye and how it behaves At its center is the fovea, a pit that is most sensitive to light and is responsible for our sharp central vision. The central retina is cone- dominated and the peripheral retina is rod-dominated. Limitations of the visual field 130 degrees vertically, 180 degrees horizontally (including peripheral vision)

Eye Movements serve two major functions Eye Movements Saccades to Fixations – Position target objects of interest on the fovea Duration 10ms - 120ms Very fast (up to 700 degrees/second) No visual perception during saccades Tracking – Keep fixated objects on the fovea despite movements of the object or head eye movement video Eye Fixations perceptions are gathered during fixations 90% of the time the eye is fixated duration: 150ms - 600ms Video examples: 1 | 2 | 3 | The eye and how it behaves

Questions: What happens to the visual image? How do we get information out of the image? How do we connect visual images (from different fixations)? One answer : have a memory storage separate from the visual image itself Iconic Memory Video example

Iconic Memory Is there scientific evidence for iconic memory? The number of items that can be accurately perceived at a glance The number of objects that can be attended to at once Problem: If the info decays quickly, subjects don ’ t have enough time to report it.

Iconic Sensory Store your iconic memory does this… …but faster! If I show you this…. Reports of “ seeing ” a scene after it disappeared This introspective description was suggestive of some kind of " single, visible, precategorical, high-capacity, quickly-decaying memory that holds incoming visual stimulation for further processing " (Loftus & Irwin, 1998).

Iconic Memory George Sperling (1960) Believed that he can see more than he can report The limitation is not in storing the information but in reporting it Solved this problem (span limit problem) and supported the existence of iconic memory Used two techniques: whole report partial report

50 msec Report Cue Iconic Memory Whole Report: Presented a 4 x 3 matrix of letters and digits for 50 ms, and asked subjects to report all the items they saw.

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Iconic Memory Whole Report: Subjects are shown an array of items and asked to report all the items they saw. ANPL KMDT WBSR so 9/12 would be = 75% accuracy Results: Subjects could not report more than about 4.5 items on each trial. (4.5/12 = 38%) held true over wide range of exposure durations ( sec)

50 msec Report Cue Iconic Memory Partial Report: 4 x 3 matrix of letters for 50 ms, subjects report all the items from one particular row. He cued them which row to report by playing a high, medium, or low tone. (I have horn, drum, pong)

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Iconic Memory Partial Report: Subjects are shown an array of items and asked to report a subset of the items they saw. BMCK NVPA WJUL So 3/4 = 75% accuracy Results: Subjects could typically report all 4 items on each trial. (4/4= 100%)

Iconic Memory So far we’ve addressed capacity of iconic memory, what about duration, how long does it last? Effect of delay of tone Report Cue Varied time between the disappearance of the display and the onset of the cue tone: 0 to 1 sec

Iconic Memory Results: With short delays, can report proportionately more, but with longer delays partial report performance is similar to whole report Report Cue

Iconic Memory Conclusions from Sperling (1960): Evidence of iconic memory Properties: High capacity of information Very short duration (lasts about.5 sec) Pre-categoical (“raw,” unprocessed) information (we’ll return to this)

Iconic Memory Memory vs. afterimage of the eye?

A little on color vision Trichromatic theory of color vision “ Blue ” “ Green ” “ Red ” Blue Wavelength Input ConesSignal to Brain Yellow Equal Parts Red and Green =

A little on color vision Trichromatic theory of color vision Opponent Process Theory Red opposes Green (Red + Green) opposes Blue Explains color afterimages

Iconic Memory Banks and Barber (1977) Similar to Sperling methodology If using a retinal after-image then letters with complimentary colours would be reported Red becomes Green Yellow becomes Blue K J F S B N E W P red 50 msec presentation short interval (250 msec) report cue Results : -their data showed subjects can recall correctly with a color cue

Iconic Memory Is the information in iconic memory “unprocessed?” Pre-categorical report: based on sensory properties (location/color) Post-categorical report: based on categorical properties (type of item - letters or digits) Von Wright (1972) Merikle (1980)

Iconic Memory Von Wright ( 1972) Used partial report method with different report criteria type (numbers vs letters) color location Is info in iconic memory pre-categorical?

Iconic Memory BUT Merikle (1980) used different kinds of displays (perceptual groupings, letters, and numbers) and found that the partial report advantage for type (number vs letter) as strong as location So it ’ s possible info processed to some degree

Problems with Iconic Memory 1.Information may not be precategorical e.g., Merikle (1980) 2.The idea of output interference rather than decay. Dick (1971) found that the first item was reported correctly equally often for whole and partial reports. The act of recalling one item can interfere with recall of the next item, so the more items you're required to report, the less likely you are to report the last one successfully 3.The types of errors that the subjects make. Auditory confusion errors (e.g. if letter is B, subjects more likely to report V than R) Mewhort & Leppman (1985) – identification (‘T’ was there or not) error rates didn’t increase with duration between display and probe

Sensory Memory 4.An important distinction: Stimulus persistence: Something that looks or sounds like the stimulus continues to be present for a short amount of time after the stimulus is no longer present Information persistence : Information can be extracted from a stimulus for a short amount of time after the stimulus is no longer present Early view: stimulus persistence and information persistence were basically the same thing. But more recent research suggests that: Stimulus persistence reflects residual neural activity after exposure to a stimulus Information persistence reflects the same type of memory that is used for longer-lasting information

Echoic Memory Sensory memory for auditory information Not as much research done on echoic memory as iconic

The ear and how it behaves Changes in Air Pressure Stimulus is much more linear and transitory

Echoic Memory Darwin, Turvey, and Crowder (1972) Whole report: report all 3 lists For partial report, the cue was: - light on the left = report left speaker list - light on the right = report right speaker list - light in the center = report list that was The interval from list offset to cue onset was: - 0 seconds, 1 second, or 4 seconds

Echoic Memory Findings: Partial report advantage up until about 4 sec so echoic memory lasts 4 s or more Echoic memory holds less than iconic memory Darwin, Turvey, and Crowder (1972)

Echoic Memory Some of the Effects discovered in study of echoic memory Using Immediate Serial Recall tasks Presented a list of items and asked to recall them in the order in which they were presented Recency effect Modality effect Suffix effect Note: while these effects were discovered in the study of echoic memory, they are currently believed to reflect general memory principles rather than exclusively features of echoic memory

Echoic Memory Recency effect - last item of list better remembered than items earlier in the list

Echoic Memory Suffix effect - recency effect disappears if an auditory item follows last list item Typical Suffix Effect experiment has 2 conditions: Control condition list of auditory items presented. Suffix condition the same, except that each list is followed by a spoken word. Why the effect? Interference from last item disrupts memory trace

Echoic Memory Modality effect - last item of list better remembered when presented aloud than visually or silently Why? Acoustic information persistence lasts approx. 2 seconds -- unless a subsequent similar stimulus interferes with it. When the subject reports the last item, it is still present in echoic memory. In contrast, visual stimulus persistence doesn't last that long.

Sensory Memory Summary (1)Capacity - limited only by amount of info that can be received by the perceptual system (e.g., eye, ear) (2) Duration of memory: - iconic - up to about 1 sec - echoic - about sec depending on type of info (3) Type of info - mostly pre-processed, but some processing may occur after ms