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