why are we motivated to forget?
- environmental cues bring to mind traumatic memories
- forgetting is beneficial
- retain a positive outlook towards life: positivity bias
positivity bias
- tendency to recall more pleasant memories than either neutral or unplesant ones
- increases over the lifespan
positivity bias study: Charles, Mather, and Carstensen (2003)
Charles, Mather, and Carstensen (2003)
task:
- younger and older adults viewed pictured of pleasant, neutral, and unpleasant scenes
- recall the pictures - after 15-minutes delay
result:
- older adults recalled about twice as many positive than negative images
- recognition, however, was equal for both positive and negative images
why does positivity bias increase with age?
- as wer get older our focus:
- shifts away from future goals
- maintain a sense of well-being - older people are more skilled in emotion regulation:
- goal-driven moniitoring
- evaluating, altering and gating (letting in or out) emotinoal reactions and memories
- better control of what we remember
motives alter what we remember and we get better at it with age
motivated forgetting terminology
Repression: (Freud)
- psycological defense mechanism aimed at rejecting
- keeping out of consciousness
- repressed material still influences behaviour
- unconscious
supression:
- conscious process
- intentional, goal directed
- “intentional forgetting”
Psychogenic amnesia
- profound forgetting
- psychological in origin
- often triggered by trauma
- lacks observable neurobiological basis
- memory for public events and general knowledge often remain intact
- ability to form new memories intact
possible mechanism:
extreme psychological distress -> involuntary suppression retrieval in relation to certain stimuli
limit encoding
way to control what we remember
- look away from stimulus
- focus on pleasant aspects
- stop elaborative thoughts
prevent retrieval
way to control what we remember
- intentionally shift to new thought
- avoid cues/reminders
stop retrieval
way to control what we remember
in the face of a reminder
- actively suppress the unwanted memory
Directed Forgetting: Item Method
Basden and Basden (1996)
Directed forgetting is observed on:
- recall tests
- recognition tests
effect reflects differences in episodic encoding (instuction before encoding)
- remember instructions: elaborative
- forget instructions: release attention
suggested “forget” instruction engages an active process that disrupts encoding
encoding suppression
active process adopted at encoding and restrict which experiences we allow into memory
- RT evidence + fMRI evidence
why do we need encoding suppression?
- regulates which experiences will be allowed into memory
- life has difficulties -> reducing the footprint of negative experiences is always good
- bias in remembering more positive than negative characteristics about oneself, but matched when relating to another (Sedikides & Green, 2000)
- regulate memory to protect self image
Directed Forgetting: List-Method
learn new list - interference with old
Geiselman, Bjork & Fishman, 1983
instruction to forget: (after encoding)
costs - forget instructions impair recall of items from first list
benefit: reduce proactive interference expected on the second list
differences in retrieval, not encoding
- disappear in recognition tests
- appear in implicit tests
naturalistic diary study
task:
- students recorded 2 events/day in a diary for 1 week
- 1 group asked to forget previous weeks entries and focus on new events in second week
- 1 group asked to remember events from 1st week and new events in second
- recall events from both weeks
results:
the forget group had relatively poorer memory for
- first week events
- example items that neither group thought they would have to recall
- both negative and positive mood events
Retrieval inhibition hypothesis - mechanism of list method directed forgetting
forget instructions inhibit list 1 items
- reduces the activation of unwanted memories
- however they remain available
representing forgotten items restores their activation levels
- explains why items can be recognized but not recalled
context shift hypothesis - mechanism of list method directed forgetting
forget instructions mentally separate list 1 and list 2 items
- the mental context shifts between the lists
- list 2 context lingers into final test
- new context is a poor retrieval cue for list 1 items
may involve inhibition of the unwanted content
context shift hypothesis study: Sahakyan and Kelley, 2002
context shifts led to worse recall of a former list (even without forget instruction)
- part of the directed-forgetting effect arises from as shift in mental context
Inhibitory control: Behaviour/action control
the ability to initiate, discontinue, or prevent motor actions based on goals
Go/No-Go Task:
measures inhibitory control over action
- press a button whenever a letter appears on the screen
- if the letter is an “X” (rare) withhold the response
inhibitory control: cognitive control
the ability to flexibly control thoughts in accordance with our goals - includes ability to stop unwanted thoughts from entering mind
Think/No-think task:
- measures inhibitory control over memory
- can people use inhibitory control to prevent unwanted memory?
think/no think paradigm
total control effect:
- think>no think
- intentional control yields lasting retrieval consequences
positive control effect:
- think > baseline
- reminders without intention to suppress facilitate memories
negative control effect:
- no think > baseline
- reminders with intention to suppress inhibit memories
memory suppression (think no think)
- suppression increases with more suppression trials per event
- replication with various stimulus combos
- suppression occurs with neutral and unwanted memories, but unclear if emotional memories are more/less suppressible
- after a single suppression forgetting lasts at least 24 hours
- people with diminished cognitive control show less suppression induced forgetting
inhibitory control and PTSD - Catarino et al., 2019
is inhibitory control impaired in PTSD
hyp - PTSD patients will be less able to suppress
results:
- suppression was diminished in the PTSD group conpared with the control group
- retrieval suppression was most compromised in people with the most severe symptoms
spontaneous recovery (memory)
the re-emergence of a previously extinguished conditioned response after a delay in classical conditioning (Pavlov)
- increases with time, though rarely returns to full strength
- suffers diminishing returns with increasing recovery/extinction cycles
- occurs in conditioned emotional responding
- the stronger the initial memory, the more likely to recover
why do memories recover spontaneously?
if retroactive interference reflects inhibition of responses that had previously been relevant:
- forgotten memories recover when inhibition is gradually released
- MacLeod and Macrae found that inhibition appears to decrease over time
- retrieval induced forgetting is significantly reduced after a 24 hour delay
