Interrogations-and-Confessions-Handbook

390 A Psychology of Interrogations and Confessions
were repeated on day two (29–35 hour group) and day three (47–50 hour group).
No significant differences in memory recall were found between conditions on
either suggestibility scale. Nor did sleep loss significantly affect distortions and
fabrications in relation to the verbal memory recall. As far as the suggestibility
scores were concerned, Yield 1 was not affected by sleep loss, whereas Yield 2,
Shift and Total Suggestibility all increased significantly with sleep loss. The
effect sizes for Total Suggestibility were 0.49 and 0.75 for one and two nights
of sleep deprivation, respectively.
The results of these studies show that sleep deprivation does increase suggestibility,
particularly after negative feedback, and the longer the sleep deprivation
the more suggestible people become. This has important implications for
police interviewing.
SUGGESTIBILITY: DISSOCIATION AND FANTASY PRONENESS
Three studies have investigated the relationship between suggestibility and
dissociation, using the Dissociation Experiences Scale (DES; Bernstein &
Putnam, 1986). In the first study, Wolfradt and Meyer (1998) correlated the
Yield 1, Shift and Total Suggestibility scores from the German translation of
the GSS 2 with the overall DES score among 37 patients with anxiety disorders
and 45 normal controls. The correlations were only significant among the normal
subjects. Yield 1 correlated highly significantly (r = 0.66, p < 0.001) with
dissociation, but no significant correlation was found for Shift (r =−0.10, ns).
A small, but significant, correlation was found between Yield 1 and mental
absorption (r = 0.33, p < 0.05), as measured by the Tellegen Absorption Scale
(TAS; Tellegen & Atkinson, 1974). No correlations were reported between GSS
2 immediate recall and dissociation and absorption.
In a replication dissociation study, using the Dutch translation and validation
of the GSS 1 (Merckelbach, Muris, Wessel & Van Koppen, 1998a), Merckelbach,
Muris, Rassin and Horselenberg (2000) investigated the relationship of
suggestibility with the DES, the Cognitive Failure Questionnaire (CFQ; Broadbent,
Cooper, Fitzgerald & Parkes, 1982) and the Creative Experiences Questionnaire
(CEQ; Merckelbach et al., 1998b). Fifty-six women undergraduate
students completed all four tests. A significant correlation was found between
the DES and Yield 1 (r = 0.29, p < 0.05), Total Suggestibility (r = 0.37, p < 0.01)
and immediate recall (r =−0.30, p < 0.05). The CFQ correlated significantly
with Shift (r = 0.27, p < 0.05) and Total Suggestibility (r = 0.36, p < 0.01). No
significant correlations were found between suggestibility and fantasy proneness,
as measured by the CFQ. Interestingly, the correlations between the GSS
1 and DES all became non-significant after the relationship with CFQ had been
partialled out.
These two studies show that dissociation proneness is significantly correlated
with Yield 1, but not with Shift. The finding that controlling for the influence of
self-reported cognitive failures reduced the correlations between dissociation
and Yield 1 and Total Suggestibility suggests that the relationship between
suggestibility and dissociation is in part mediated by perceptions of memory