limits, and it was suggested that the hypothesised relationship
between vividness of visual imagery and picture memory performance | would be more likely to be apparent in this situation. In the
previous experiment, this predicted relationship became apparent when the Eg errors on only the five most 'difficult' stimulus
categories were considered, the variance contributed by errors on the 'easier* categories masking the covariance between vividness of visual imagery and picture memory performance.
However, in the present experiment because of the larger number of subjects, the predicted relationship is clearly
apparent when all categories are included in the analysis. However, to enable a direct comparison with the results of the earlier experiment, the above analysis was carried out with respect to total errors on the 'difficult' categories,
89, Sg, Sq and Sg only. The following results were obtained: (a) Control group
Correlation betv/een Eg errors and:-
(i) Total W I Q score r = 0«38 (ii) Eyes open W I Q score r = 0.53 (iii) Eyes closed W I Q score r = 0.14 (b) Experimental group
Correlation between Eg errors and:- (i) Total W I Q score r = - 0.27 (ii) Eyes open W I Q score r * - O.I4
(iii) Eyes closed W I Q score r = - 0.3
These results are extremely interesting, as while the
absolute values of the experimental group correlations are
reduced they all remain negative. However, on these 'difficult'
categories, all the equivalent correlations for the control group
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become positive, with one value reaching 0.53, Thus, this
analysis reveals a clear divergence of performance between the experimental and control subjects when the performance require ments of the task are greater. On these ’difficult* categories, good picture memory performance tends to be associated with a greater degree of vividness of visual imagery as determined by the VVIQ. This finding is in accordance with Mark’s (1973) results, i.e. that ’good* visualisers perform better on picture memory tasks than * poor’ visualisers. In contrast, as predicted by the present theory, in the dual-task situation a greater
degree of vividness of visual imagery, as determined by the VVIQ, is associated with poorer performance on the picture memory task.
The above theoretical considerations, and the outcome of
the associated analysis related to two separate performance situations provide considerable evidence in support of Mark’s
claim for the validity of the VVIQ as a useful index of vividness of visual imagery. Quite different predictions derived from
analysis of the tv/o separate experimental situations aooordnng
to the present theory were confirmed. This analysis was concerned with the functional role of the imagery system, and
the transference of these theoretical concepts into empirical predictions was dependent upon the validity of the VVIQ as a quantitative index of imagery. The confirmation of these
predictions indicates that the VVIQ is both a valid and useful ’measure’ of individual differences in vividness of visual
imagery.
(vii) Sex differences
There were no significant differences between mean W I Q scores for male and female subjects in either the experimental or control groups. ^
(viii) The internalised cognitive task
As in the previous experiment, few subjects scored even
a small number of correct solutions on this task over the 50 trials, because of the limited time allowed for each problem.
However, all subjects performed extremely well and conscientiously in the experiment. The requirement of thinking aloud presented
few difficulties to subjects. Monitoring of the subjects’ vocalisations by the experimenter showed that, on the whole, the subjects were obeying the experimental instructions to the best
of their abilities. The subjects maintained a smooth flow of
a
vocalisation when the slide was presented. Occasional prompting
from the experimenter between trials ensured that this require ment was kept in mind at all times by the subjects. The
sustained concentration and very long testing sessions required
for this experiment were mentally fatiguing for both subject and
experimenter, but no subject abandoned meaningful attempts to solve the mental arithmetic problems, even towards the end of
the testing session, and there was no tendency for errors to increase over the testing time period. The ’thinking aloud’
requirement fulfilled its intended purpose most successfully.
5.9 Conclusions
The experiment reported in this chapter replicated almost exactly the findings of the similar experiment reported in
chapter IV, The effects observed proved resistant to changes
in methodology, and the adoption of more powerful and extensive
ÿ
controls, together with the larger numbers of subjects in the present experiment, confirmed and increased the validity of the previous findings over a wide range of different analyses.
The main results of the two experiments are highly significant, and strongly support the theoretical concepts
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developed earlier in this thesis, together with the experimental
strategies and methodologies derived from these concepts. Some
a
new effects have been demonstrated which, in addition to theirbearing on the present theoretical approach, are relevant to other areas of investigation.
Concerning picture memory, for example, the results of
the experiments using the two-stage recognition procedure in relation to a series of heterogeneous stimulus categories, each
represented by sets of homogeneous pictures, indicate that,
although picture memory is undoubtedly extremely powerful, the
argument of Goldstein and Chance (1970), that the power of picture memory has been somewhat overestimated in the literature,is
correct. (see p.79). The present experiments have demonstrated that two picture memory performances based only on recognition of heterogeneous pictures may appear to be identical, when the use of a second error index in relation to the identification of a previously learned picture in its totality may show that the two performances are, in fact,significantly different.
Secondly, the successful utilisation of the VVIQ indicates the worth of its use as a research tool in experiments concerned in any way with visual imagery. The present experiments go
considerably further than typical studies which attempt only to relate good visual memory, or visual learning performance, to high levels of vividness of visual imagery. It appears that the index of imagery provided by the VVIQ is sufficiently robust to be usefully applicable to a wide range of experimental