Thema 6: Implicit Memory & Skill Learning / Thema 7:
Consolidation & Forgetting
Gluck, M. A., Mercado, E., & Myers, C. E. (2016). Chapter 8: Skill memory: Learning by doing (pp. 311-350).
This chapter describes how repeated experiences can incrementally enhance the performance of a skill by gradually modifying
memories of how the skill can best be executed. Repeated experiences not only can change how a person performs a skill, they
also can change the structure of the brain circuits that are used to perform that skill. Skill memories are formed and processed
by several brain regions, including the basal ganglia, the cerebral cortex, and the cerebellum. People with damage in one or
more of these brain regions have trouble learning new skills as well as performing skills already learned.
8.1 Behavioural Processes
• Skill: ability to perform a task that has been honed through experience
o Perceptual motor skills - driving, dancing, drinking out of a glass - learned movement patterns and perceptual
abilities
o Cognitive skills - playing cards, budgeting, taking tests - require you to solve problems or apply strategies
• Features of skill memories
Skill memories are similar to episodic and semantic memories but have some unique qualities: they are long lasting and
improved by repeated experiences but can't always be verbalised (nondeclarative). They may be acquired and retrieved
without the feeling of remembering associated with recalling episodic memories (implicit).
o How different are cognitive from perceptual-motor skill memories?
Closed skills involves performing predefined movements that never vary, whereas open skills involves movements
that are made on the basis of predictions about changing demands of the environment. Most perceptual-motor
skills contain both aspects of closed and open skills.
Cognitive skills are usually portrayed as more depending on intellectual prowess whereas perceptual-motor skills
are often more thought to depend on physical dexterity, speed and strength - but the mechanisms for improving
these skills are quite similar (repetition, learning strategies).
o Which comes first, cognitive or perceptual-motor skill memory?
First humans learn perceptual-motor skills at younger ages, than they learn cognitive skills. Many cognitive skills
(including reading and writing), are difficult or impossible to acquire without first learning basic perceptual-motor
skills (such as producing speech or drawing lines).
o Can nonhumans have cognitive skill memories?
Humans are not the only animals that can learn cognitive skills. Experimenters have taught primates and other
animals to use various tools. There is also recent evidence that animals in the wild can teach themselves to use
tools. Still, not all animals are equally capable of learning complex cognitive and perceptual-motor skills.
• Encoding new memories
How do different kinds of practice affect performance and retention of skill memories? And why are individuals who are
great at one skill not necessarily as good as other, similar skills?
o More repetition does not guarantee improvement
Early psychological theories of skill learning suggest that the more times you perform a skill, the faster or better
you'll be able to perform that skill in the future. However, research shows that feedback is critical to the
effectiveness of practice (knowledge of results). The power law of practice holds that the degree to which a
practice trial improves performance diminishes after a certain point, so the additional trials are needed to further
improve the skill (learning occurs quickly at first, then slows). This does not depend on the skill being practiced but
is a simple mathematical function. Feedback or observational learning can help overcome this power law.
Frequent feedback in simple perceptual-motor tasks leads to good performance in the short term but mediocre
, performance in the long term, whereas infrequent feedback leads to mediocre performance in the short term but
better performance in the long term. It also really depends on the task and the person.
o Timing and sequencing of practice matters
Feedback is critical to the acquisition of skill memories because it affects how individuals perform the skills during
practice, and the same holds for instruction. Skill memories also depend on how practice time is apportioned:
• Massed practice (concentrated continuous practice) generally produces better performance in the short term
• Spaced practice (spread out over several sessions) often leads to better retention in the long run.
The same holds for the kind of practice:
• Constant practice (limited set of materials and skills), repeatedly practicing the same skill
• Variable practice (more varied materials and skills), consists of practicing a skill in a wider variety of conditions and
leads to better performance on later tests (but can lead to slower progress)
The timing, variability and ordering of training trials can be as important as the quality of feedback and amount of
practice.
o Skill memories are often formed unconsciously
• Explicit learning: learning a skill and are able to verbalise how it is done
• Implicit learning: learning without being aware that learning has occurred.
Implicit skill learning has been studies in individuals with anterograde amnesia and in people without brain
damage. It seems that people with anterograde amnesia improve with each trial, although they think they're doing
it for the first time. A task that is commonly used by psychologists to study implicit skill learning without brain
damage is the serial reaction time task. In this task the participants learn patterns without awareness that there is
a pattern.
People often have trouble verbalising what they have learned after mastering a perceptual-motor skills -
suggesting that they are more likely to be learned implicitly, but also cognitive skills can be learned implicitly.
There is currently no was to assess whether implicit learning is more likely to occur during the learning of
perceptual-motor skills or cognitive skills.
There is no very clear line between implicit and explicit learning, but more of a continuum. For acquiring skills at an
expertise level however, it seems clear that conscious awareness is needed.
o Expertise requires extensive practice
When practicing a skill, the goal is usually to become better - performance becoming more controlled and
effortless/ automatic or reflex-like you could say, although those are inborn. Sequences of movements that an
organism can perform virtually automatically (with minimal attention) are called motor programs (or habits).
Unlike reflexes, these motor programs can be either inborn or learned. To determine whether a skill has become a
motor program is to interrupt the action sequence and observe the results. Highly learned perceptual-motor skills
and cognitive skills could become motor programs (multiplication skills for example).
This means that you first have to put some effort in when learning a skill - using instruction, observation, trial &
error etc. this is called the cognitive stage. The second stage in skill acquisition is the associative stage, in this
stage you begin to use stereotype actions and rely less on actively recalled memories of rules. The last stage is the
autonomous stage - in which you reach high levels of performance and movement patterns become quick and
effortless. In this stage the skill have become motor programs. This model of skill acquisition is developed by Fitts
and it provides a useful framework for relating skill performance and expertise to practice. The model suggests that
skill memories may rely on different memory processes as practice progresses.
Some researchers suggest that practice alone determines expertise, but there are other things that might be
important too, such as perceptual learning.
o Talent takes time to blossom
People who seem to master a skill with little effort are often described as talents, but even they learn to perform
those skills. There might be a role of genetics in skill learning and performance. Twin studies show that the more
practice someone has, the more their performance differences are due to genetic accounts. (twins performance
became more similar), but this is only assessed on simple perceptual-motor skills (rotary pursuit task).
• Retrieving existing memories
Transfer specificity is the restricted applicability of some learned skills to specific situations - the transfer of learned
abilities to novel situations depends on the number of elements in the new situation that are identical to those in the
, situation in which the skills were encoded (identical elements theory). It is also closely related to transfer-appropriate
processing (memories of facts and events instead of skills).
Acquiring the ability to learn novel tasks rapidly based on frequent experiences with similar tasks is called learning set
formation (learning-to-learn). It occurs in infants learning basic perceptual-motor skills and in adults learning more
complex motor skills. It can play an important role in the development and application of cognitive skills.
• When memory fails
The memorability of a skills depends on the complexity of the skills, how well it was encoded, how often it has been
performed and on the conditions in which recall is attempted. Although skill memories can last a lifetime, they do
deteriorate with non-use. The retention of perceptual-motor skills is better than retention of cognitive skills. The
forgetting is skills is however not very much researched. The loss of a skill through non-use is called skill decay, and
follows similar patterns as in the forgetting of memories for events and facts. In some ways, forgetting a skill is like
learning it in reverse - forgetting curves are similar to learning curves. How does forgetting happen> it can be the passage
of time but it can also result when new memories interfere with the recollection of old memories.
8.2 Brain Substrates
What neural systems do humans need to acquire memories of perceptual-motor and cognitive skills? All movements and
postures require coordinated muscle activity. A major function of the nervous system is to initiate and control patterns of
muscle activity. The spinal cord and brainstem play a role in performance of perceptual-motor skills by controlling and
coordinating movements. Brain regions dedicated to sensation and perception (sensory cortices) are also involved, by
processing information that contributes to the guidance of movements. Especially the somatosensory and visual systems are
important for learning perceptual-motor skills.
In the next section it is described how practicing skills can change neural circuits. Sensory processing and motor control by
circuits in the spinal cord are clearly necessary for learning and performing perceptual-motor skills. However, the core elements
of skill learning seem to depend on three other areas of the brain: the basal ganglia, the cerebral cortex and the cerebellum.
When any of these become dysfunctional, the performance and learning of both cognitive and perceptual-motor skills become
seriously impaired.
The basal ganglia and skill learning
The basal ganglia is a collection of ganglia (clusters of neurons) that lie at the base of the forebrain (most prominent part of the
brain). They are positioned close to the hippocampus, and receive a large number of inputs from the cortical neurons, which
provide the basal ganglia with information about sensory stimuli the person is experiencing. These cortical inputs are initially
processed by the dorsal striatum (subregion of the basal ganglia). The basal ganglia sends signals to the thalamus (affecting
interactions between neurons in the thalamus and motor cortex) and brainstem (influencing signals sent to the spinal cord). By
modulating these motor control circuits, the basal ganglia play a role in initiating and maintaining movement.
The basal ganglia are particularly important for controlling the velocity, direction and amplitude of movements, as well as for
preparing to move. Disruption of activity in the basal ganglia impairs skill learning, so, researchers suspect that processing in the
basal ganglia is a key step in forming skill memories. Practicing a skill can change how basal ganglia circuits participate in the
performance of that skill and synaptic plasticity is a basic neural mechanism enabling these changes.
• Learning deficits after lesions
Much of what is known about the role of basal ganglia in skill learning comes from studies of rats learning to navigate
mazes (like the radial maze). For the original task - where rats need to remember certain aspects of past events (in what
wing he had already taken food) rats with hippocampal do very badly but rats with basal ganglia damage do as well as
rats with no damage at all. When you slightly alter this experiment - like illuminating arms that have food. In this case,
rats with hippocampal damage do a lot better since they can associate illumination with the food but rath with basal
ganglia damage have difficulties with this, it seems to prevent rats from learning the perceptual-motor skill of avoiding
dark arms and entering illuminated arms.
These and other experiments have led researchers to conclude that the basal ganglia are important in perceptual-motor
learning that involves generating motor responses based on specific environmental cues. The basic assumption is that
there is nothing unique about the way the basal ganglia function in rats, so it should be the same for humans. In this way
enhanced basal ganglia function may facilitate skill learning.
• Neural activity during perceptual-motor skill learning
Measures of neural activity in the basal ganglia during learning provide further clues about the role of the basal ganglia in
the formation of skill memories. 4 basic patterns of neural activity in the basal ganglia found in rats during the T maze:
o Some neurons fired most at the start of a trial, when rats were first released into the maze
o Some fired most when instructional sound was broadcasted
o Some responded strongly when the rat turned left or right
o Some fired at the end of the trial, when the rat received food.
As performance improved, the percentage of neurons that showed task-related activity patterns increased to about 90%
with most neurons firing strongly at the beginning and at the end of the task rather than during. These measurements
show that neural activity in the basal ganglia changed during the learning of a perceptual-motor skill, suggesting that
encoding or control of skills by the basal ganglia changes as learning progresses. The increased neural activity seen in the
beginning and end states suggest that the basal ganglia developed a motor plan that was initiated at the beginning of
