The development of memory PS 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 EpisodicSemantic AutobiographicalGeneral factual info Autonoetic consciousNoetic consciousness Mentally 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

Double Dissociation STM- LTM? Amnesia patients: Patient KF (Shallice & Warrington, 1970) STMLTM STM

Working Memory (WM) Baddeley (2000 )

The development of memory The development of STM The development of WM The development of LTM

The development of STM Source: Dempster, 1981, Figures 1-3, 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 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? Episodicsemantic 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