Accuracy on practice problems and on a test one week later, by practice type
| Performance on Practice Problems | Accuracy |
|---|---|
| Interleaved practice | 60% |
| Blocked practice | 89% |
| Performance on Test | Accuracy |
| Following interleaved practice | 63% |
| Following blocked practice | 20% |
This passage is adapted from Steven C. Pan, “The Interleaving Effect: Mixing It Up Boosts Learning.” ©2015 by Scientific American.
We’ve all heard the adage: practice makes perfect! In other
words, acquiring skills takes time and effort. But how exactly
does one go about learning a complex subject such as tennis,
calculus, or how to play the violin? An age-old answer is:
practice one skill at a time. A beginning pianist might rehearse
scales before chords. A tennis player practices the forehand
before the backhand. Learning researchers call this “blocking,”
and because it is commonsensical and easy to schedule,
blocking is dominant in schools and training programs.
However, another strategy promises improved results. Enter
“interleaving,” a largely unheard-of technique that is capturing
the attention of cognitive psychologists and neuroscientists.
Whereas blocking involves practicing one skill at a time before
the next (for example, “skill A” before “skill B” and so on,
forming the pattern “AAABBBCCC”), in interleaving one
mixes, or interleaves, practice on several related skills together
(forming for example the pattern “ABCABCABC”). For
instance, a pianist alternates practice between scales, chords,
and arpeggios, while a tennis player alternates practice between
forehands, backhands, and volleys.
Given interleaving’s promise, it is surprising then that few
studies have investigated its utility in everyday applications.
However, a new study by cognitive psychologist Doug Rohrer
takes a step towards addressing that gap. Rohrer and his team
are the first to implement interleaving in actual classrooms. The
location: middle schools in Tampa, Florida. The target skills:
algebra and geometry.
The three-month study involved teaching 7th graders slope
and graph problems. Weekly lessons were largely unchanged
from standard practice. Weekly homework worksheets, however,
featured an interleaved or blocked design. When
interleaved, both old and new problems of different types were
mixed together. Of the nine participating classes, five used
interleaving for slope problems and blocking for graph
problems; the reverse occurred in the remaining four. Five days
after the last lesson, each class held a review session for all
students. A surprise final test occurred one day or one month
later. The result? When the test was one day later, scores were
25 percent better for problems trained with interleaving; at one
month later, the interleaving advantage grew to 76 percent.
These results are important for a host of reasons. First, they
show that interleaving works in real-world, extended use. It is
highly effective with an almost ubiquitous subject, math. The
interleaving effect is long-term and the advantage over
blocking actually increases with the passage of time. The
benefit even persists when blocked materials receive additional
review. Overall, the interleaving effect can be strong, stable,
and long-lasting.
Researchers are now working to understand why
interleaving yields such impressive results. One prominent
explanation is that it improves the brain’s ability to tell apart
concepts. With blocking, once you know what solution to use,
the hard part is over. With interleaving, each practice attempt is
different from the last, so rote responses don’t work. Instead,
your brain must continuously focus on searching for different
solutions. That process can improve your ability to learn
critical features of skills.
A second explanation is that interleaving strengthens
memory associations. With blocking, a single strategy,
temporarily held in short-term memory, is sufficient. That’s not
the case with interleaving—the correct solution changes from
one practice attempt to the next. As a result, your brain is
continually engaged at retrieving different responses and
bringing them into short-term memory.
Both of these accounts imply that increased effort during
training is needed when interleaving is used. This corresponds
to a potential drawback of the technique, namely that the
learning process often feels more gradual and difficult at the
outset. However, that added effort can generate better, longer-
lasting results.
We’ve all heard the adage: practice makes perfect! In other
words, acquiring skills takes time and effort. But how exactly
does one go about learning a complex subject such as tennis,
calculus, or how to play the violin? An age-old answer is:
practice one skill at a time. A beginning pianist might rehearse
scales before chords. A tennis player practices the forehand
before the backhand. Learning researchers call this “blocking,”
and because it is commonsensical and easy to schedule,
blocking is dominant in schools and training programs.
However, another strategy promises improved results. Enter
“interleaving,” a largely unheard-of technique that is capturing
the attention of cognitive psychologists and neuroscientists.
Whereas blocking involves practicing one skill at a time before
the next (for example, “skill A” before “skill B” and so on,
forming the pattern “AAABBBCCC”), in interleaving one
mixes, or interleaves, practice on several related skills together
(forming for example the pattern “ABCABCABC”). For
instance, a pianist alternates practice between scales, chords,
and arpeggios, while a tennis player alternates practice between
forehands, backhands, and volleys.
Given interleaving’s promise, it is surprising then that few
studies have investigated its utility in everyday applications.
However, a new study by cognitive psychologist Doug Rohrer
takes a step towards addressing that gap. Rohrer and his team
are the first to implement interleaving in actual classrooms. The
location: middle schools in Tampa, Florida. The target skills:
algebra and geometry.
The three-month study involved teaching 7th graders slope
and graph problems. Weekly lessons were largely unchanged
from standard practice. Weekly homework worksheets, however,
featured an interleaved or blocked design. When
interleaved, both old and new problems of different types were
mixed together. Of the nine participating classes, five used
interleaving for slope problems and blocking for graph
problems; the reverse occurred in the remaining four. Five days
after the last lesson, each class held a review session for all
students. A surprise final test occurred one day or one month
later. The result? When the test was one day later, scores were
25 percent better for problems trained with interleaving; at one
month later, the interleaving advantage grew to 76 percent.
These results are important for a host of reasons. First, they
show that interleaving works in real-world, extended use. It is
highly effective with an almost ubiquitous subject, math. The
interleaving effect is long-term and the advantage over
blocking actually increases with the passage of time. The
benefit even persists when blocked materials receive additional
review. Overall, the interleaving effect can be strong, stable,
and long-lasting.
Researchers are now working to understand why
interleaving yields such impressive results. One prominent
explanation is that it improves the brain’s ability to tell apart
concepts. With blocking, once you know what solution to use,
the hard part is over. With interleaving, each practice attempt is
different from the last, so rote responses don’t work. Instead,
your brain must continuously focus on searching for different
solutions. That process can improve your ability to learn
critical features of skills.
A second explanation is that interleaving strengthens
memory associations. With blocking, a single strategy,
temporarily held in short-term memory, is sufficient. That’s not
the case with interleaving—the correct solution changes from
one practice attempt to the next. As a result, your brain is
continually engaged at retrieving different responses and
bringing them into short-term memory.
Both of these accounts imply that increased effort during
training is needed when interleaving is used. This corresponds
to a potential drawback of the technique, namely that the
learning process often feels more gradual and difficult at the
outset. However, that added effort can generate better, longer-
lasting results.