Interrogations-and-Confessions-Handbook

Suggestibility: Empirical Findings 363
such as forensic patients and court referrals, typically score more than one
standard deviation below the mean for normal subjects (i.e. a score about
12 with a standard deviation of 7), even when their intellectual functioning
is not known to be impaired.
2. Delayed recall. Delayed recall of the GSS narrative is usually obtained
about 50 minutes after immediate recall. As with immediate recall, the
maximum number of correct ‘ideas’ is 40. Memory on the GSS narratives
typically deteriorates by about one or two points over a 50 minute period,
which gives mean delayed memory scores of 19 and 10 for normal and
forensic subjects, respectively. This means that verbal memory deteriorates
about 10% within one hour. However, among normal subjects about 75% of
the immediate recall is retained at one week follow-up (Singh & Gudjonsson,
1984; Tata & Gudjonsson, 1990) and about 40% is produced at four
week follow-up (Sigurdsson et al., 1994).
Immediate and delayed recall on the GSS 1 and GSS 2 deteriorate with
advanced age, particularly in old age where the deterioration is very marked
(Sigurdsson et al., 1994).
3. Yield 1. Yield 1 refers to the number of suggestions the subject yields to on
the GSS 1 and GSS 2 prior to negative feedback. The maximum score the
subject can obtain is 15. The mean score on the GSS 1 for normal subjects
is 4.6 with a standard deviation of 3. A Yield 1 score of 11 or above falls
outside the normal range (i.e. the 95th percentile rank). Forensic patients,
including court referrals, typically obtain a Yield 1 score of about 6, with a
standard deviation of 3.5.
4. Shift. Shift refers to the number of times where there has been a distinct
change in the subject’s answers following negative feedback. The wording
of the negative feedback, which is administered immediately after the 20
questions have been asked (Yield 1), is:
You have made a number of errors. It is therefore necessary to go through the
questions once more, and this time try to be more accurate.
This should be stated firmly, but not sternly. Subjects typically change some
of their answers after they have been told that they have made a number of
errors during the 20 questions. The direction of the change is irrelevant in
the scoring of Shift. The highest possible Shift score on the GSS 1 and GSS
2 is 20 (i.e. all 20 questions are included in the scoring of Shift, unlike Yield
1 and Yield 2). The mean Shift score for normal subjects on the GSS 1 is
about 2.9, with a standard deviation of 2.5. This means that a score of 8 or
above falls outside the normal range. The mean score for forensic patients,
including court referrals, is about 4 with a standard deviation of 3.
5. Yield 2. Yield 2 refers to the number of leading questions which the subject
yields to after the negative feedback has been administered. Therefore,
Yield 2 represents the number of suggestions accepted after interrogative
pressure. Yield 2 indicates the type of change that has occurred as a result
of the negative feedback. Usually, the change (i.e. Shift) is in the direction
of increased suggestibility. That is, after negative feedback and repeated
questioning subjects tend to yield more to the leading questions than they