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The development of memory
PS39382012-2013
Dr Harry Purser
Outline
• What is memory?• Memory systems• Memory models• When does each system emerge in
development?
What is memory?
• Memory = learning
• 3 processes:– Encoding– Storage– Retrieval
Memory structures
• Atkinson & Shiffrin (1968): multi-store model
Long-term Memory (LTM)
Episodic versus semantic
Episodic SemanticAutobiographical General factual infoAutonoetic conscious Noetic consciousnessMentally re-experiencing the event
You don’t know when you’ve learned it
e.g. What did you have for breakfast this morning?
e.g. Who is PM?
Procedural system
• Implicit, cannot verbalise it• Associative, as opposed to rule-based• Skills & habits:
– Riding a bike– Complex grammar rules
• With practice, info from EM can become procedural (e.g. Driving a car)
Development of LTM
• Infants amnesia• Immature temporal lobes• But infants can remember:
– Auditory stimuli (Cherournet et al., 2002)– Objects and actions up to 1 week (Rovee-Coolier,
1993)
Sensory memory
• Only 3 seconds or less• Is it worth further processing?• Classic experiment by George Sperling (1960):
Short-term Memory (STM)
• Storage for around 20 seconds• Rehearsal can ‘refresh’ STM indefinitely• Visual or verbal
• George Miller (1956): The magical number seven, plus or minus two 5-9
• Cowan (2001): 4 is the limit: 2-6
Overcoming STM limitations
• Chunking: grouping together related item in 1 unit
• 00323677253553• 00-323-677-25-3223
Double Dissociation STM- LTM?
• Amnesia patients:
• Patient KF (Shallice & Warrington, 1970)
STM LTM
LTMSTM
Working Memory (WM)• Baddeley (2000)
The development of memory
• The development of STM• The development of WM• The development of LTM
The development of STMSource: Dempster, 1981, Figures 1-3, 66-68
• Memory capacity increases?
• Acquisition of strategies?• Support from long-term
memory (knowledge)?• Improved attention?
The development of WM
• Does the structure of WM develop?• Do all components of the WM develop
together, or independently?
• Gathercole et al. (2004):• 719 children aged 4 to 15• Working Memory Test Battery for children
Results Gathercole et al. 2004
• Performance on all sub-tests increased with CA.
• Organisation of WM: factor-analysis:
• From 6-years onwards: WM is adult-like in structure
Testing procedural memory in infants
• Mobile conjugate reinforcement (MCR) procedure (Rovee-Collier):– Infants placed in a
crib with a stand and a mobile attached.
Mobile conjugate reinforcement
• Procedure (for 2- 3-month-olds):
• Baseline phase: Ribbon attaches baby’s foot to the stand (3 mins). Kicking rate is measured
• Learning phase: Baby’s foot attached to mobile (9 mins). Kicking now activates mobile!
• Non-reinforcement phase: Baby’s foot attached to stand (3 mins)
Mobile conjugate reinforcement
• Same procedure is undertaken next day
• Long-term retention test: babies given baseline procedure again at a later date… will they attempt to move the mobile by kicking??
• Findings from > 30 years of research (see Rovee-Collier & Hayne, 2000) show…
Mobile conjugate reinforcement
• From 2-months, babies show procedural memory for the contingency over 2 days
• If 2-month-olds are given 3 training sessions, their memory extends to 2 weeks
• By 6-months, memory extends to 2 weeks
• Also, if given ‘reminders’, memory is extended in 2- 6-months
Mobile conjugate reinforcement
• However: memory is context-dependent in first 6 months:
• If the mobile or the setting (e.g., crib lining) are different during the test phase, memory not retained
• Only from 12-months is memory context-independent: ability to abstract?
Development of declarative system
• Deferred imitation: infants required to reproduce a modelled action, without practice, following a delay
• Success indicates semantic memory because modelled action is only seen once and infant can’t practice
• Therefore, no opportunity for procedural memory to be used
• Infant must have a mental representation of the model’s behaviour, and retain that representation over time (Piaget, 1962)
Testing semantic memory in infants
Findings from deferred imitation studies:
1. From 6 months, infants show deferred imitation of simple actions after 24h (e.g., Hayne et al., 2000)
1. By 9-months, recall of sequences of actions extends to 4 weeks and keeps rising with age (e.g., Bauer et al., 2000; Carver & Bauer, 2001)
1. Long-term retention is unaffected by practice (Meltzoff, 1995) - shows memory is not procedural
Dissociation episodic/ semantic?• Episodic semantic memories (squire, 1992)
• No: two very separate systems (Tulving, 1995)
• Vargha-Khadem et al. 1997:• Double dissociation in patients• Two different systems
Dissociation in children
• Free recall: episodic• Cued recognition: semantic• Perner & Ruffman (1995):
– 58 children aged 3-6 on a picture memory task– All children better at cued recall– Awareness of source of belief (“I know it’s soft
because I felt it”) was associated with free recall
– Evidence that episodic memories develop later?
• Gentner (1988): a shift occurs at 6/7 from perceptual to relational interpretation of metaphor (“plant stems are like drinking straws”)
• Goswami (1996): as soon the relevant knowledge is there, children can use it to understand relational comparisons
• Do children have knowledge organised in an adult fashion (relations) or is it immature (perceptual)
Relational shift debate
Comparison task: “The Sun is like...?”
Categorisation task: “The Sun is the same kind of thing as...?”
•
Comparison & categorisation
• 3-yrs+ could distinguish meaningful similarity statements from anomalous
• 4-yrs+ also showed knowledge of conventional categories assumed to be transgressed in nonliteral comparisons
Vosniadou & Ortony (1983)
Thomas et al. (2010)
Summary
• Memory develops• Working memory improves, but adult
structure is in place in children• Long-term memory develops, but the
structure may change over time