Interrogations-and-Confessions-Handbook

358 A Psychology of Interrogations and Confessions
important. In his view, personality characteristics, such as intelligence, are only
important when extreme.
Irving draws our attention to the potential importance of the seriousness of
the crime:
In practice as long as the crime involved is relatively serious then all suspects,
regardless of their individual proclivities, will tend to produce a level of attention
sufficient to the task (Treisman, 1969), except where mental handicap or drug
intoxication makes that impossible for them. Custodial interrogation does tend to
focus the mind (p. 23).
Irving’s bold assertion is based on an assumption rather than empirical facts.
It is not clear why he refers to Treisman’s (1969) article in support of his argument,
because the article only deals with attention in the context of subjects
being presented with more information than they can handle. The article does
not deal with the critical components of attention which are relevant to police
interrogation, such as vigilance, arousal and motivation.
CONCLUSIONS
The early experimental work of Cattell (1895) demonstrated the influence of
suggestion upon human testimony. However, it appears to have been Binet
(1900) who first introduced the idea of interrogative suggestibility and provided
a conceptual framework for testing it. Before his work both French and German
psychologists had known about the effects of suggestion upon sensation and
perception, particularly in connection with hypnosis.
Many tests were developed to measure different types of suggestibility. Most
of these appear to have had no clear theoretical base or rationale. Later workers
factor analysed the results from these tests in an attempt to understand the
nature of suggestibility. They discovered that there were at least two types of
suggestibility, referred to by Eysenck and Furneaux (1945) as ‘primary’ and
‘secondary’. ‘Primary’ suggestibility consisted of so-called ‘ideo-motor’ tests and
correlated highly with hypnotizability. ‘Secondary’ suggestibility appeared to
measure a much more varied and complex phenomena and was shown to be
less stable and reliable. All the factor analytical studies, with the exception
of those conducted by Stukat (1958), failed to include tests of interrogative
suggestibility. This resulted in interrogative suggestibility being a neglected
area of research.
Interrogative suggestibility is a special type of suggestibility and differs from
other types of suggestibility in several important ways. Most significantly, it involves
a questioning procedure that is typically concerned with past experiences
and events, recollections and remembered states of knowledge. This makes it
very different to suggestibility concerned with motor and sensory experiences
of the immediate situation.
There are two main theoretical approaches to interrogative suggestibility.
These are called the ‘experimental’ and ‘individual differences’ approaches.