Klaus Oberauer – Personal Web Page Contact:
k.oberauer “at” bristol.ac.uk
Klaus Oberauer – Personal Web Page Contact:
k.oberauer “at” bristol.ac.uk
This page gives an
overview of my current research interests, with links to publications for
download
Supplementary
material to Oberauer & Lewandowsky (2008), Psychological Review, can be found here
What
is working memory capacity?
Why is
working memory capacity limited?
The
architecture of working memory
Age differences
in working memory
Can
we think two things at once?
Mental
models in deductive reasoning
What is working memory
capacity?
When talking about working memory capacity, we assume
that there is one capacity limit underlying many different observed limitations
on cognitive performance. Evidence for this contention comes from factor
analytic studies showing that many different ways of measuring working memory
capacity load on the same or closely related factors
Oberauer, K., Süß, H.-M., Schulze, R.,
Wilhelm, O., & Wittmann, W. W. (2000). Working memory capacity - facets of a cognitive ability construct. Personality
and Individual Differences, 29, 1017-1045. Download the task battery here (in German!)
Moreover, the factor
or factors reflecting the common variance of several working memory tasks are
excellent predictors of reasoning performance:
A further study suggests that working memory capacity is closely related
to the speed of information processing, as reflected by the drift-rate
parameter of the diffusion model applied to two-choice reaction-time tasks
Collaborators
on these studies were Heinz-Martin
Süß, Oliver
Wilhelm, Ralf Schulze,
Florian
Schmiedek, and Werner
W. Wittmann
Why is working memory
capacity limited?
Several mechanisms have been proposed for why we
forget information in working memory, and why tasks become harder the more
separate elements we need to hold in mind simultaneously. Reinhold
Kliegl and I investigated some of the most commonly suggested mechanisms in
a common formal modelling framework: limited activation resources, time-based
decay, interference due to confusion between items (“crosstalk”), and
interference due to overwriting of representations. A model based on
interference through overwriting provided the best fit to the data.
In a follow-up paper, we refined the interference model and embedded in a
non-linear mixed-effects (nlme) modeling
framework, which allowed us to estimate parameters on the group level and the
level of individuals simultaneously.
Together with Steve Lewandowsky I tested three
computational models of serial recall that represent three assumptions about why
information in working memory is forgotten: temporal distinctiveness,
time-based decay, and interference. Again, the interference model did best.
Supplementary material can be downloaded here:
Summary of unpublished
experiments
Elke Lange and
I provided some direct evidence for feature overwriting as a cause of
interference in working memory. Words and nonwords are recalled worse when a
distractor task involves other words or nonwords that share many phonemes with
the memory word.
Overwriting can be understood as a loss of bindings
between features of an object (e.g., a word) in working memory. I assume that
working memory capacity is essentially the limited capacity to establish and
maintain temporary bindings between features to form objects, and bindings
between objects to form new structures. Preliminary evidence for the idea that
individual (and age) differences in working memory capacity are related to the
ability to maintain bindings can be found in the following papers:
If unreliable
bindings make representations vulnerable to interference through overwriting,
then people with low working memory capacity should experience more
interference between similar (i.e., highly overlapping) representations. An
attempt to pin down similarity-based interference between contents of working
memory and representations used in a distractor task was, however, not very
successful:
Working memory capacity is not only determined by the
causes of forgetting but also the mechanisms to prevent or counteract it. Annekatrin
Hudjetz and I have provided evidence that there must be at least two such
mechanisms, articulatory rehearsal and attention-based refreshing. The latter
can operate concurrently with reading aloud irrelevant material.
Many tasks used to measure working memory involve
recall of lists in serial order. Maintenance of order – either in time or in
space – is an instance of binding memory contents to locations in their
spatio-temporal context. One of the most robust phenomena in serial order
recall is the serial position curve. Here is my attempt to disentangle the
factors that produce primacy and recency in short-term serial recall and
related recognition tasks (I’m not sure we really understand them yet, but I
try to be optimistic sometimes):
The
Architecture of Working Memory
The main function of working memory seems to be to
provide the representations needed in complex cognitive tasks. This involves
selection of relevant representations in long-term memory, constructing new
combinations and structures, and selectively accessing individual
representations for manipulation. Building on previous work by Nelson Cowan, I proposed a
framework for the architecture of working memory that consists of three
embedded components: (1) the activated part of long-term memory, responsible
for making potentially relevant information easy to retrieve, (2) the region of
direct access, responsible for establishing new bindings to build new
structural representations, and (3) the focus of attention, responsible for
selecting one representation at a time for processing. Details of the framework
and evidence supporting it can be found here:
Age Differences in Working
Memory
A large part of the decline of cognitive abilities in
older age can be attributed to reduced working memory capacity. My colleagues
and I have made a few attempts to pin down which function of working memory is
impaired in old age, using the three-component framework of working memory
outlined above. It seems that old adults have specific problems with resisting
intrusions from activated but irrelevant representations in long-term memory,
and with maintaining information in the region of direct access, but no
difficulties with switching the focus of attention from one object in working
memory to another.
Can
we think two things at once?
Usually not.
Cognitive operations must be done one at a time, this limitation is often
described as a bottleneck. With considerable practice on combining a numerical
and a spatial working memory updating task, young adults can learn to do these
two operations simultaneously without mutual interference. A further study has
shown that old adults cannot acquire this skill.
Mental Models in Deductive Reasoning
The theory
of mental models developed by Phil
Johnson-Laird and Ruth Byrne describes deductive reasoning as based on
semantic representations, that is, representations of the situation that is
described by the premises (i.e., mental models). One of my interests is in how
people integrate the information in separate premises into a single mental
model. Premises in deductive reasoning tasks often describe a relation between
two objects or events. We found that relational premises have an inherent
directionality, that is, they instruct listeners to construct a model of the
relation by placing the two elements in working memory in a particular order,
starting with the reference object (or relatum) and adding the target object.
As a consequence, integrating two premises is easier if the first premise
already contains the relatum of the second premise, so that the target object
of the second premise can simply be added in the prescribed relation to the
model of the first premise.
Other research
investigated the role of working memory capacity in the ability to construct complex
mental models of spatial relations. I assume that working memory capacity
reflects the ability to build new structural representations. It follows that
people with low working memory capacity should have difficulties constructing
complex mental models. This is what we found.
What do we mean
by saying, for instance, “If I do one more experiment, I will understand how
people reason”? One view, prominent in theories of human reasoning that are
inspired by formal logic and semantic, is that conditionals express the
material conditional. The material conditional is defined by a truth table: “If
p then q” is true in three possible cases: (1) p and q are both true, (2) p is
false and q is true, and (3) p is false and q is false. The mental models
approach to reasoning with conditionals is built on this idea. The material
conditional view has been criticized by many philosophers and psychologists,
and the alternative many of them propose is that the conditional “if p then q”
expresses a high conditional probability of q, given p. The above sentence
would then mean that my probability of understanding how people reason is high,
given that I do one more experiment. Some of my research together with Oliver
Wilhelm focused on distinguishing between these views. We found that the
majority of people understands the conditional in terms of the conditional
probability, but a minority understands it differently, in a way that could be
explained by the mental models approach.
Research with
realistic conditionals referring to people’s world knowledge has repeatedly
shown that logically valid inferences from a conditional are blocked when
people can think of counterexamples to the conditional premise. The idea that
reasoners search for counterexamples and accept a conclusion only if they don’t
find any originates in the mental-model theory, but the probabilistic view of
conditionals would predict the same effect, because counterexamples diminish
the conditional probability of the consequent, given the antecedent. Sonja
Geiger and I found a way to tease apart these explanations, and found support
for the probabilistic explanation.
The probabilistic
approach does not fare that well when it comes to explain reasoning, however.
It seems that whether people accept or reject inferences from conditional
premises depends more on whether they can think of counterexamples than on
their degree of belief in the conditional, as determined by the conditional
probability. The theory of mental models alone also cannot explain the
reasoning data. The best account so far is provided by a dual-process model,
with one process using probabilistic information and the other using
analytical, model-based thinking.
Another line of
research has tested a specific version of the probabilistic approach to
conditionals, the theory of Oaksford and Chater
(1998, 2001) on the Wason four-card selection task. This theory did not fare
very well…