School of Psychology
Professor Richard Kemp
Cognitive Bias: Psychology and Forensic Science
Professor Bryan Found
Cognitive Bias:
Psychology and Forensic Science
• What is Cognitive Bias and why does it occur?
• Why am I so illogical?
• Can I avoid cognitive Bias?
• Can we manage Cognitive Bias
• Implications for Forensic Science practice
We construct the world we live in
•
Our experience of the world comes via
our sense organs
•
The data arriving through our sense
organs is incomplete and ambiguous
•
We need to disambiguate the
information we receive
•
We form hypotheses about the world
around us
Sometimes we get it wrong!
Read this
12
And this
13
All in the mind
•
So, the world you perceive is only in
your head
•
The reality you experience is a
construction – a best guess
interpretation of the limited, ambiguous
information made available to you
•
But there is lots of stuff you don’t even
see
And then there is memory…
•
Our memory is not a veridical
record of an event
•
What we remember depends
on previous experience, mood,
attention, motivation,
emotional state, time delay,
past recall, post-event
information etc. etc.
We can’t always remember what we saw
I am going to show you a list of words
Look at the words and try to memorise them
snooze
silence
pillow
dream
night
tired
quilt
rest
Write down all the words you saw on the list
Who remembered the word NIGHT?
Who remembered the word DREAM?
Who remembered the word SLEEP?
Cognitive Biases
•
Systematic patterns of thinking that
may lead us to reason in an illogical
manner
•
These stem directly from the way in
which we construct the world we
experience
•
We need to make sense of the data
presented to us, and our approach isn’t
always logical
A few examples (Wikipedia!)
•
Availability heuristic: The tendency to
overestimate the likelihood of events with
greater "availability" in memory, which can
be influenced by how recent the memories
are or how unusual or emotionally charged
they may be
•
Base rate fallacy: The tendency to ignore
base rate information (generic, general
information) and focus on specific
information (information only pertaining to a
certain case).
•
•
Anchoring: The tendency to rely too heavily,
or "anchor", on one trait or piece of
information when making decisions
Confirmation bias: The tendency to search
for, interpret, focus on and remember
information in a way that confirms one's
preconceptions
•
Backfire effect: The reaction to disconfirming •
evidence by strengthening one's previous
beliefs.
Experimenters bias: Tendency for
experimenters to believe, certify, and publish
data that agree with their expectations..
A few more…
•
Framing effect: Drawing different conclusions •
from the same information, depending on
how that information is presented
False consensus effect: The tendency for
people to overestimate the degree to which
others agree with them
•
Hindsight bias: The tendency to see past
•
events as being predictable at the time those
events happened
•
Illusory correlation: Inaccurately perceiving a
relationship between two unrelated events
•
Fundamental attribution error: The tendency
for people to over-emphasize personalitybased explanations for behaviours observed
in others
•
Omission bias: Tendency to judge harmful
actions as worse, or less moral, than equally
harmful omissions (inactions)
•
Zero risk bias: Preference for reducing a
small risk to zero over a greater reduction in
a larger risk.
Naive realism: The belief that we see reality
as it really is – objectively and without bias;
that the facts are plain for all to see; that
rational people will agree with us; and that
those who don't are either uninformed, lazy,
irrational, or biased.
Why are we so illogical?
•
Cognitive biases are often adaptive
•
They can be useful heuristics
•
They provide thinking short-cuts
•
However, where we require logical,
evidence based thinking, we need to
be aware that this is not our normal
mode of operation
Common Cognitive Bias Fallacies
•
I know all about Cognitive Bias, but I am an
expert so am not affected
•
I know all about Cognitive Bias, but I think
about this carefully to make sure I am not
affected
•
I know all about Cognitive Bias, but I have
years of experience so am no longer affected
•
I know all about Cognitive Bias, but I always
check my results with my colleagues…
•
I know all about Cognitive Bias, but its critical
that I have access to this information
Exposure to essential and extraneous
information
•
Forensic Scientists need access to
some information (“Forensicicate this
for me”)
•
But how much of this information is
really essential
•
It can be difficult, but we need to
control the flow of information form the
investigator to the Forensic scientist
•
If not, there is the danger of Bias and
also Double counting of evidence
Double counting of evidence
•
If a forensic science is valid then it has some
value to an investigation, independent of
other sources of information
•
If a fire scene analyst can look at a scene
and tell whether an accelerant was used
then this is valuable
•
But what if s/he also knows that the owner of
the premises was in financial difficulty,
recently increased their insurance cover, and
was filmed buying cans of petrol
•
If they use this information to influence their
conclusion then the jury will effectively hear
this evidence twice and it will be double
counted
Cognitive Bias and Forensic Pathology
•
You are the experts, not me
•
I can describe the problem and explain
how important it is
•
I can offer some potential solutions and
point out what wont work
•
But only you can work out the best
strategy within your profession
Controlling Cognitive Bias:
Actuarial vs Clinical assessments
So what can I do?
Accept: Accept this is a feature of the way
we all think.
Believe: Don’t try to deny it or explain it
away
Control: Instead, introduce controls to the
way you work to check and try to limit
the impact of these biases
Document: Describe what information you
were exposed to and when, and
explain why its important to know this.
Describe how cognitive biases may
affect your conclusions
See Found, B., & Edmond, G. (2012). Reporting on the
comparison and interpretation of pattern evidence:
recommendations for forensic specialists. Australian
journal of forensic sciences, 44(2), 193-196.
Control
•
Manage the flow of information in your
workplace
•
Explain to investigators what you want to
know and what you don’t want to know
•
Consider a “Sequential unmasking”
approach
•
Carefully record your opinions at each stage
of the process – remember these will change
once you are exposed to new information
and you wont remember what you thought
previously
•
Peer Review and Wisdom of crowds: Only if
independent decisions
Cognitive Bias:
Psychology and Forensic Science
• What is Cognitive Bias and why does it occur?
• Why am I so illogical?
• Can I avoid cognitive Bias?
• Can we manage Cognitive Bias
• Implications for Forensic Science practice
Cognitive Bias:
Psychology and Forensic Science
• What is Cognitive Bias and why does it occur? : That’s the way we are built!
• Why am I so illogical?
• Can I avoid cognitive Bias?
• Can we manage Cognitive Bias
• Implications for Forensic Science practice
Cognitive Bias:
Psychology and Forensic Science
• What is Cognitive Bias and why does it occur? : That’s the way we are built!
• Why am I so illogical? : Because biases can be useful short-cuts
• Can I avoid cognitive Bias?
• Can we manage Cognitive Bias
• Implications for Forensic Science practice
Cognitive Bias:
Psychology and Forensic Science
• What is Cognitive Bias and why does it occur? : That’s the way we are built!
• Why am I so illogical? : Because biases can be useful short-cuts
• Can I avoid cognitive Bias? : No, not unless you stop being human!
• Can we manage Cognitive Bias
• Implications for Forensic Science practice
Cognitive Bias:
Psychology and Forensic Science
• What is Cognitive Bias and why does it occur? : That’s the way we are built!
• Why am I so illogical? : Because biases can be useful short-cuts
• Can I avoid cognitive Bias? : No, not unless you stop being human!
• Can we manage Cognitive Bias : Yes – with careful design of work practices
• Implications for Forensic Science practice
Cognitive Bias:
Psychology and Forensic Science
• What is Cognitive Bias and why does it occur? : That’s the way we are built!
• Why am I so illogical? : Because biases can be useful short-cuts
• Can I avoid cognitive Bias? : No, not unless you stop being human!
• Can we manage Cognitive Bias : Yes – with careful design of work practices
• Implications for Forensic Science practice : This is up to you – but don’t ignore it
Essential reading
Useful reading
•
Found, B., & Edmond, G. (2012).
Reporting on the comparison and
interpretation of pattern evidence:
recommendations for forensic
specialists. Australian journal of forensic
sciences, 44(2), 193-196.
•
Edmond, G., Martire, K., Kemp, R.,
Hamer, D., Hibbert, B., Ligertwood, A., ...
& Thompson, M. (2014). How to crossexamine forensic scientists: a guide for
lawyers. Aust. Bar Rev, 39, 174-196.
•
Edmond, G., Found, B., Martire, K.,
Ballantyne, K., Hamer, D., Searston, R., ...
& Tangen, J. (2016). Model forensic
science. Australian Journal of Forensic
Sciences, 48(5), 496-537.
Questions?
Contact:
Professor Richard Kemp
School of Psychology
University of New South Wales
Sydney 2052
Australia
Email: [email protected]
Phone: 0415430668