The Psychology Book (57 page)

COGNITIVE PSYCHOLOGY 181

See also:
René Descartes 20–21 ■ George Armitage Miller 168–73 ■

Daniel Schacter 208–09 ■ Frederic Bartlett 335–36

Donald Broadbent

Born in Birmingham, England,

Donald Broadbent considered

himself to be Welsh, since he

spent his teenage years

in Wales after his parents’

divorce. He won a scholarship

to the prestigious Winchester

A World War II plane
incorporates a

Broadbent was influenced in his

College, then joined the Royal

dazzling display of informational data;

thinking about how we process

Air Force aged 17, where he

Broadbent was interested in discovering

information by another product of

trained as a pilot and studied

how pilots prioritized information and

wartime research: the development

aeronautical engineering.

what design changes would aid this.

of computers and the idea of

After leaving the RAF in

“artificial intelligence.” The first

1947, he studied psychology

planes, the lever for pulling up the

director of the APU, Kenneth

under Frederic Bartlett at

wheels was identical to the one for

Craik, had left the unit important

Cambridge, then joined the

pulling up the flaps, and the two

manuscripts and flow diagrams

newly founded Applied

were situated together under the

comparing human and artificial

Psychology Unit (APU),

becoming its director in 1958.

seat; this led to frequent accidents.

information processing, which

Married twice, he was a shy,

Broadbent thought these incidents

Broadbent clearly studied.

famously generous man whose

could be avoided if the capacities

At the same time, code breakers

“puritanical streak” led him

and limitations of the pilots were

such as the mathematician Alan

to believe that his work was

taken into consideration during

Turing had been tackling the notion

a privilege and should always

the design process, rather than

of information processing, and in

be of real use. In 1974, he

surfacing at the point of use.

the postwar period he applied this

was awarded the CBE and

Broadbent was interested in

to the idea of a “thinking machine.”

appointed a fellow of Wolfson

using psychology not only to design

The comparison of a machine to

College, Oxford, where he

better equipment, but also to reach

the workings of the brain was a

remained until his retirement

a better understanding of what

powerful analogy, but it was

in 1991. He died two years

affected the pilots’ capabilities.

Broadbent who turned the idea

later of a heart attack, aged 66.

They clearly had to cope with large

around, considering the human

amounts of incoming information,

brain as a kind of information-

Key works

and then had to select the relevant

processing machine. This, in

1958
Perception and

data they needed to make good

essence, is what distinguishes

Communication

decisions. It seemed to him that

cognitive psychology from

1971
Decision and Stress

mistakes were often made when

behaviorism: it is the study of

1993
The Simulation of Human

there were too many sources of

mental processes, rather than their

Intelligence

incoming information.

manifestation in behavior. ❯❯

182 DONALD BROADBENT

To study how our attention works,

use to “filter out” the irrelevant

Broadbent needed to design

information from the masses of

experiments that would back up

data we receive through our senses

his hunches. His background in

all the time. Following the air traffic

engineering meant that he would

control model, he chose to present

not be satisfied until he had

aural (sound-based) information

Our mind can be conceived

evidence on which to base a theory,

through headphones to the subjects

as a radio receiving many

and he also wanted that research

of his experiment. The system was

channels at once.

to have a practical application.

set up so that he could relay two

Donald Broadbent

The APU was dedicated to applied

different streams of information at

psychology, which for Broadbent

the same time—one to the left ear

referred not only to therapeutic

and one to the right—and then test

applications, but also to applications

the subjects on their retention of

that benefited society as a whole;

that information.

he was always very conscious that

As Broadbent had suspected, the

his research was publicly funded.

subjects were unable to reproduce

could only effectively deal with one

all the information from both

One voice at a time

message at a time. What interested

channels of input. His feeling that

One of Broadbent’s most important

him was the mental process that

we can only listen to one voice at

experiments was suggested by his

must take place in order for them to

once had been confirmed, but still

experience with air traffic control.

select the most important message

the question remained as to exactly

Ground crew often had to deal with

from the various sources of incoming

how the subject had chosen to retain

several streams of incoming

information. He felt that there must

some of the incoming information

information simultaneously, sent

be some kind of mechanism in the

and effectively disregard the rest.

from planes arriving and departing,

brain that processes the information

Thinking back to his initial

which was relayed to the operators

and makes that selection.

training as an engineer, Broadbent

by radio and received through

The experiment that Broadbent

suggested a mechanical model to

headphones. The air traffic

devised, now known as the dichotic

explain what he felt was happening

controllers then had to make quick

listening experiment, was one of

in the brain. He believed that when

decisions based on that information,

the first in the field of selective

there are multiple sources of input,

and Broadbent had noticed that they

attention—the process our brains

they may reach a “bottleneck” if the

brain is unable to continue to process

all the incoming information; at this

point, there must be some kind of

“filter” that lets through only one

channel of input. The analogy he

uses to explain this is typically

practical: he describes a Y-shaped

tube, into which two flows of ping

pong balls are channeled. At the

junction of the two branches of the

tube, there is a flap that acts to

block one flow of balls or the other;

this allows balls from the unblocked

channel into the stem of the tube.

Air traffic controllers
have to deal

with a multitude of simultaneous

signals. By re-creating this problem in

listening experiments, Broadbent was

able to identify attention processes.

COGNITIVE PSYCHOLOGY 183

A question still remained, however:

at what stage does this filter come

into operation? In a series of

Our short-term

experiments that were variations

Information from all

memories are like

on his original dichotic listening

the senses is fed in...

a
Y-shaped tube
.

tasks, Broadbent established that

information is received by the

senses and then passed on in

its entirety to some kind of store,

which he called the short-term

memory store. It is at this stage, he

believes, that the filtering occurs.

...which creates a

His description of how and when

“bottleneck”
where

information must be

information is selected for attention

filtered...

is known as the “Broadbent Filter

Model,” and it demonstrated a

completely new approach to

experimental psychology, not only

in combining the theoretical with

the practical, but also in considering

the workings of the brain as a form

...so that only
one
stream

of information processing.

of information
is

processed.

The cocktail party problem

Broadbent was not the only person

to address the problem of selective

attention. Another British scientist,

Colin Cherry, also investigated the

many conversations to give our

important implications when

subject during the 1950s. Working

attention to, and which to ignore?

applied to air traffic control, for

in communication rather than

And how is it possible to be

example, where decisions could

psychology, Cherry posed what he

distracted from our focused

be made on possibly irrelevant or

called the “cocktail party problem:”

attention on conversation “A”

inaccurate information, rather than

how, at a party where lots of people

by conversations “B” or “C”?

being prioritized according to

are talking, do we select which of

To help answer these questions,

meaning and importance.

Broadbent turned his attention to

Broadbent and Cherry worked

the nature of the filter in his model.

together on many dichotic listening

Precisely what information does

experiments to test the filtering

it filter out, and what does it allow

process. They realized that filtering

through? Following another process

is also affected by expectation. In

of rigorous experimenting, he found

one experiment, participants were

that the selection is made not on

asked to listen to different sets of

One of the two voices is

the content of the information (what

numbers presented simultaneously

selected for response without

is being said), but on the physical

to each ear. In some cases they

reference to its correctness,

characteristics of any message,

were instructed which ear (the

and the other is ignored.

such as clarity or tone of voice.

information channel) they would

Donald Broadbent

This suggests that even though

be asked about first; in others no

information is stored, albeit very

instructions were given. The

briefly, in short-term memory, it

results showed that when people

is only after filtering that it is

know which ear is receiving the

processed for meaning and actually

stream of information they will

understood. This finding had

be asked for first, they switch ❯❯