emotional arousal and persuasion effects in flooding

Behav. Res. & Therapy, 1973, Vol. 11, pp. 587 to 598. Pergamon Press. Printed in England

EMOTIONAL AROUSAL AND PERSUASION EFFECTS IN FLOODING*

ANDREW MATHEWS and PHYLLIS SHAW

University Department of Psychiatry, Warneford Hospital, Oxford, England

(Received 1 Junuary 1973)

Summary-The effects of a single session of imaginal flooding were studied in female students unable to touch a harmless spider. All combinations of continuous vs. discontinuous presentation and highly arousing vs. less arousing material were used in a factorial design, to test the hypothesis that highly arousing material is beneficial only when presented under massed conditions. Results were clearly against prediction and suggested that immediate attitude change was maximal following less arousing material, irrespective of method of presentation; while behaviour change was greatest when less arousing material was presented continuously.

In a second experiment, subjects were exposed to both types of theme material in either a low-high or a high-low order. Some evidence was found for the postulated attitude changes and contrast effects, which favoured the use of a high-low order. Possible explanations for earlier contradictory evidence, and implica- tions for clinical treatment are discussed.

IN MARKED contrast to the consistent therapeutic effects found with desensitization, the results from studies of flooding (or implosion) treatment have been confusing and contradictory. Some apparently well-controlled studies have shown that flooding treatment is at least as effective as desensitization (e.g. Barrett, 1969) while others have found flooding to be less effective than desensitization, and no more effective than control procedures (e.g. Mealiea and Nawas, 1971). It is difficult to reconcile opposing findings without as- suming that there must be some uncontrolled differences between studies accounting for the observed variation. Examination of the studies already published suggests a number of possibly relevant factors, including the anxiety level experienced by subjects, the duration of flooding themes or sessions, and so on.

It can be postulated that the therapeutic effect of flooding is maximal if moderately intense anxiety is elicited during the treatment session, but that continuous presentation of phobic material is accompanied by a progressive diminution in response. Such an anxiety decrement, and subsequent therapeutic behavioural change, could be due to any one of a number of effects or to a combination of them-for example, extinction or habituation under massed conditions, emotional exhaustion, cognitive contrast effects, and so on. Continuous presentation of flooding material is thus expected to be effective provided that anxiety is at first elicited and subsequently decreased during exposure to phobic material, while on the other hand, the discontinuous presentation of highly arousing material might prove to be therapeutically harmful, since anxiety would repeatedly increase in the presence of phobic stimuli and decrease only in their absence. Presentations of phobic material eliciting relatively low levels of emotional response would be expected to have an effect intermediate between these two conditions, with less difference due to continuous or discontinuous presentation.

* This research was supported by the Medical Research Council, U.K. We wish to thank Professor M. G. Gelder, Dr. D. H. Gath, Dr. D. Johnston and Mrs. M. Munby for their help in carrying out this study.

587

588 ANDREW MATHEWS and PHYLLIS SHAW

In the first experiment to be described, the effects of a single session of imaginal flooding were studied under four conditions; highly arousing material presented continuously, highly arousing material presented discontinuously, less arousing material presented continuously and less arousing material presented discontinuously. It was predicted that the conditions would vary in therapeutic effectiveness, with high/massed conditions being most effective, followed by low/massed and low/spaced, while high/spaced would be least effective.

Subjects EXPERIMENT 1

Questionnaires were circulated among groups of female students in a variety of colleges for professional training. All those who admitted to fear of spiders of sufficient intensity that they judged themselves incapable of touching a harmless household spider, and who volunteered to take part in ‘an experiment on fear reduction’ were asked to attend for one experimental session and for one follow-up appointment a month later. All those who succeeded in touching a spider on initial behavioural testing were excluded from the study, and the 40 subjects located who could not touch the spider were then randomly allocated to the four experimental groups until there were ten in each group.

Materials

Two sets of flooding themes were recorded on tape, both sets consisting of six self-con- tained themes each lasting approx. 8 min. One set, designated ‘high arousal’, was recorded by a male experimenter, and was delivered in a rather dramatic and threatening manner, while the other set was recorded by a woman speaking in a rather unemotional and ‘matter- of-fact’ voice. All the themes began in a similar way and involved approximately an equi- valent amount of contact with spiders, but those in the high arousal set developed along fantastic and horrifying lines, while those in the low arousal set were fairly realistic and ended in a reassuring way. For example, a low arousal story in which a subject is asked to imagine watching and eventually touching without undue alarm a spider that she finds in a dew-covered web, was matched with a high arousal story in which the subject is described as she becomes progressively covered in webs and spiders, powerless to escape despite feeling intense fear and horror.

Both high and low versions were made up in continuous and discontinuous forms, using neutral stories (Fables For Our Time, by James Thurber) as filler items. Thus, the spaced form had a 4-min filler story followed by an 8 min spider theme, followed by a 4-min filler item and so on; while the massed form had six consecutive 4 min filler stories followed by six consecutive 8 min spider themes. In this way, each of the four complete tapes ran for just over 70 min, each having the same total time devoted to filler material and spider themes, but varying with respect to the content of the spider themes, and the continuous or discontinuous theme presentation.

Outcome measures

(1) Behaviour avoidance test (BAT). This was based on the hierarchy described by Bandura et al. (1969) slightly modified to make it suitable for work with spiders, and consisting of 17 items involving increasing proximity and eventual contact with a spider. Anxiety ratings on a ten point scale were obtained for every completed step of the BAT and these ratings were

EMOTIONAL AROUSAL AND PERSUASION EFFECTS IN FLOODING 589

averaged for all items successfully completed on both tests 1 and 2. BAT scores refer to the highest hierarchy item successfully accomplished on any one test occasion.

(2) Semantic difSerentiaZ. This consisted of 8 scales all loading on Osgood’s evaluative factor, and completed by the subject for the single concept ‘spiders’.

(3) Phobic attitude scale. This also represented a modified version of a measure used by Bandura et al. (1969) and consisted of four imaginary situations (e.g. being unexpectedly shown a short film about spiders) to be rated on a seven point scale from ‘very much like’ to ‘very much dislike’. The attitude measure was derived from the sum of the scores on all four scales, higher scores indicating a more favourable attitude.

Procedure

The subjects were asked to attend in groups ranging in size from 2 to 6, but on arrival were seated in separate rooms and were not allowed to communicate until the experiment was over. Each subject was briefly interviewed in order to acquaint her with the sequence of events constituting the experiment, and she was then instructed to fill out the semantic differential and phobic attitude scale for the first time. On completion of these forms, she was taken to the testing room by a second experimenter, who carried out the BAT. If the subject failed to touch the spider, she was allocated to an experimental group; the behavioural tester always remaining blind of this allocation.

Instructions j o the subject during this and subsequent behavioural tests were designed to avoid strong suggestions or pressure to change, but at the same time to encourage subjects to continue until the next step up the hierarchy was definitely refused or failed. Subjects were then returned to their original room and asked to fill out the semantic differential and phobic attitude measure once more, before being given earphones through which they listened to the selected flooding tape. The recorders used were situated and monitored from an adjoining room. The recorded flooding material was always preceded by general instructions on the tape, which included directions to the subject that she should involve herself as much as possible in each story and that subjective anxiety ratings on the scale already used would be requested following each spider theme. Thirty seconds was allowed after each theme for the subject to note this rating on the sheet provided.

After the tape had finished, subjects were again asked to complete semantic differential and attitude scales, the behavioural test was re-administered, and the semantic differential and attitude scales repeated for the last time. The Eysenck Personality Inventory was then given to all subjects, before appointments were arranged for follow-up interview 4 weeks later. When subjects re-attended for follow-up the post-test was repeated under identical conditions; that is, behavioural testing was preceded and followed by semantic differential and attitude scales. On completion of all measures, the purpose of the experiment was briefly outlined and any questions answered.

RESULTS

Semantic difSerentia1 and phobic attitude

Examination of treatment effects was carried out with analysis of co-variance, using the immediate post BAT 1 measures as co-variate to adjust all successive attitude scores; that is, scores obtained pre- and post-BAT 2 and pre- and post-BAT 3 (follow-up).

Mean scores for each group on the semantic differential before and after treatment and on follow-up are shown in Figure 1. No significant differences existed before treatment and

590 ANDREWMATHEWS and PHYLLIS SHAW

S. D. SCORE. 2R

26 -

M -Lo 24 _

22_ sp-LO Sp-Hi

20 - M-Hi

Ia-

5

F- ---a /-

/ / /

,’ I=

PRE POST F. u.

Fzo. 1. Mean semantic differential scores before and after each hehavioural test for the four groups in experiment 1.

there were no significant effects associated with BAT 1. Analysis of co-variance revealed a highly significant effect which favoured both low arousal groups (p < 0.001) before BAT 2, although this was no longer significant after BAT 2 or on follow-up. BAT 2 had effects varying with treatment group; low arousal groups losing some of their earlier gains, while high groups showed slight improvement.

Analysis of co-variance for the phobic attitude scale gave similar results, i.e. a main treatment effect was found which favoured both low arousal groups (p < 0.05), but which was lost after BAT 2 and on follow-up.

Behavioural avoidance test

Treatment effects were also examined by analysis of co-variance using the highest item reached in BAT 1 as a co-variate to adjust BAT 2 scores. This revealed no significant main effects, but an interaction between arousal and massed/spaced levels (p < 0.001). As can be seen in Table 1, greatest change occurred following the low/massed tape, with least change following the high/massed tape. Contrary to prediction the massing of high arousal material did not result in greater behavioural change than the spacing of the same material.

TABLE 1. MEAN BAT SCORES AND NUMBER OF ITEMS GAINED POST- TREATMENT AND ON FOLLoW-UP

High-massed High-spaced Low-massed Low-spaced

Low-High High-Low

BAT 1

11.0 12.7 11.4 11.9

11.8 10.1

Items Items gained

BAT 2 gained BAT 3 (F.U.)

11.6 0.6 12.7 1.7 14.0 1.3 14.0 1.3 13.8 2.4 14.0 2.6 13.0 1.1 13.3 1.4

12.7 0.9 - - 12.0 1.9 - -


No significant differences between the groups remained on follow-up after a 1 month interval. There were no significant differences between groups in terms of subjective anxiety during behavioural avoidance testing at any stage.

Anxiety during themes

Unexpectedly there was no overall significant difference between arousal groups in terms of reported anxiety during treatment when these data were subjected to analysis of variance. However, a significant interaction (p < 0.05) was found between arousal group and time, or theme number. Inspection of means showed that high-arousal groups experienced an initially increased level of anxiety followed by a steady decrement, and low-arousal groups a more rapid early decrease but with a sudden rise towards the end.

Correlational analysis

Correlation matrices were calculated between selected pre-treatment, within treatment treatment and outcome measures separately for the high and low-arousal groups (N = 20). The EPI scores predicted outcome to a significant degree only in the low-arousal groups; N scores correlating negatively with BAT change (-0.60).

A more direct test of the hypothesis is provided by the subjective estimates of anxiety during flooding; in the high-arousal groups average anxiety rating correlated negatively with BAT change (-0.48) the reverse direction from that predicted. Anxiety decrease was estimated by subtracting the ratings for the last three themes from those for the first three themes; this difference correlated positively with the decrease of reported anxiety during the BAT, in low-arousal groups only (f0.53).

Finally, the relationship between attitude change and subsequent BAT change was investigated. The only significant finding was that of a positive correlation between phobic attitude and BAT improvement scores in the low-arousal groups (+0.49).

Discussion

Without exception the trend of the results are wholly against the main hypothesis. In terms of reported attitude, the manner of presenting the material (massed or spaced) did not have a significant effect, but a more favourable outcome was associated with low arousal themes under either condition. Thus, it appears that flooding had different effects on subjects’ attitudes in a direction that suggests the operation of the themes as ‘persuasive messages’. In other words, the high arousal themes tended to reinforce the subjects’ conception of spiders as unpleasant and dangerous, while the low arousal themes tended to persuade subjects that spiders could be viewed as safe and interesting. In terms of behavioural change, a similar contrast is seen, with low-arousal themes associated with greatest change, though only in the massed (continuous) presentation condition. This significant interaction suggests the possibility that massing of phobic material augments the effect of the arousal value of theme content on post-treatment behaviour. The results of both attitudinal and behavioural measures therefore suggest that maximum therapeutic effect might be achieved by continuous exposure to themes involving contact with spiders but described in a relatively realistic and reassuring way.

The correlational evidence is also directly contradictory to the hypothesis that the experience of anxiety has a facilitating effect on outcome of flooding. The three significant correlations with outcome measures all point in the same direction, that high levels of anxiety are detrimental rather than facilitatory to amelioration.

592 ANDREW MATHEWS and PHYLLIS SHAW

EXPERIMENT 2

The findings of Experiment I suggested that, associated with any extinction and habituation of anxiety responses occurring during the massed exposure to phobic material, there may be some persuasion and contrast effects which influence the subjects’ response in reaI- life phobic situations encountered subsequently. This ‘persuasive message’ aspect suggested the following hypothesis:-behavioural change is maximal after massed exposure to low arousal themes because subjects in such a condition are persuaded to view spiders as more pleasant and harmless, and therefore to attempt more during post-treatment behavioural testing.

The second experiment was designed to investigate a number of specific issues arising from the conception of ffooding as a method combining at least the two following elements: massed exposure teading to the extinction or habituation of anxiety responses on the one hand; and on the other hand, a persuasive message leading to attitude changes which prepare subjects to attempt counter-phobic behaviour. Twenty students who were unable to touch a harmless household spider were exposed to six 8 min phobic themes, ten of the subjects hearing three low-arousal themes followed by three high-arousal themes (Group 1) and ten hearing the themes in the reverse order (Group 2). Specific predictions were as follows :

(1) Subjective anxiety ratings would not differ greatly across groups for the first three themes, but would diverge in the second block of three themes due to contrast effects (He&on, 1964).

(2) Autonomic activity would be generally greater during the high arousal themes; but there would be an overall response decrement which would be more marked in Group 2.

(3) Attitude measures would diverge during the first three themes; Group I improving and Group 2 deteriorating. These trends would then be reversed by the second block of themes.

(4) Post-treatment attitude, anxiety and behavioural measures would favour Group 2 (high-low) due to contrast effects and the greater recency of the more favourable persuasive message.

METHOD

Subjects, measures and procedure were similar to those used in Experiment 1, and are only discussed where differences occurred.

New forms of the flooding tapes were made up with themes separated by blank leader tapes so that rapid movement from theme to theme could be undertaken by the experimenter. Corresponding portions of the high and low arousal material were recorded on parallel tracks of a stereo-tape; with the output taken to two sets of earphones so that track one could be heard on one set while track two could be simultaneously heard on the other set.

Heart rate was determined from an E.C.C. tracing derived from standard wrist leads. Skin resistance was measured from two active ~unabraded) sites on the middle segments of


the first and second fingers of the left hand; a tetrapolar lead electrode system was used with a current density of 14 PA per square cm. Both channels were recorded using a Grass 7 polygraph.

Subjective ratings during$ooding. Forms were prepared with three ratings to be given for each theme. Each rating was to be given on a O-10 scale, with 10 representing the most extreme agreement with a given statement, and 0 representing total disagreement. The three statements were : (a) the story held my attention (b) the story made me feel tense or anxious (c) I could vividly imagine myself in the situation described.

Procedure

All testing was done by the single experimenter, and it was therefore necessary that he should remain blind of group membership. On return from behavioural testing subjects were seated together in the laboratory on comfortable chairs facing away from each other and were instructed that they should not look at or talk to each other during the experiment. Although alone during the actual presentation of flooding material, any conversation could be monitored via a microphone attached to the chair, and no subject disobeyed these instructions.

They were then asked to complete the semantic differential and phobic attitude scales for the first time, after which heart rate and skin resistance electrodes were attached. The use of the rating forms was explained, and earphones given to each subject. These were wired so that the experimenter could not tell which was playing which track, so that he remained blind of group allocation. Similarly electrode wiring was randomly varied so that he could not identify which record belonged to which subject until the experiment was over and the leads could be traced back. One minute was allowed for the three ratings at the end of each theme, and while they were being made, the experimenter wound the tape to the start of the next theme. In this way theme sequence could be varied so that a balanced order was maintained, each theme appearing an approximately equal number of times in each posi- tion. After the first block of three themes had been completed, the experimenter entered the experimental room and instructed the subjects to fill in the semantic differential phobic attitude scale for the second time. While these were being completed, he switched earphone connection plugs so that the tracks being fed to earphone sets were reversed. After the second block of three themes, semantic differential phobic attitude scales were again completed, subjects were taken individually for behavioural testing, and the attitude scales then completed for the last (fourth) time. Finally, subjects were interviewed together, so that the order of theme presentation could be checked from direct questioning as well as by following earphone leads.

RESULTS

Self ratings during Jrooding

The three subjective ratings of response to each theme were analysed using an analysis of variance for repeated measures. Overall differences between groups was extracted as a between-subject effect, while differences due to ‘arousal’ (i.e. high or low themes) and ‘replications’ (i.e. themes within each block of three) and the interaction of these effects with groups, were examined as within subject effects.

(a) Attention. The overall difference between groups was just significant (p < 0.05) with Group l-low-high-reporting higher ratings of attention. The only within subject effect

594 ANDREWMATHEWS and PHYLLISSHAW

found to be significant was that due to arousal, with the high themes associated with greater attention ratings to a highly significant degree (p < 0.001).

(b) Anxiety. No differences in reported anxiety between groups were apparent, but again a very highly significant difference emerged between arousal conditions in the predicted direction (p < 0.001). The arousal x group interaction approached significance (p < 0.10).

(c) I4uidnes.r. As with the ratings of attention, vividness ratings were higher overall in Group 1 (p < 0.05). Ratings were also very significantly higher under high arousal conditions (p < 0.001) but no other effect approached significance.

The results show quite unequivocally that subjects from both groups rated the high arousal themes as holding their attention more, making them more anxious, and evoking more vivid imagery. Inspection of subjective anxiety mean values (see Fig. 2) suggests the presence of a contrast effect for the high-low order only, but which failed to produce a clearly significant arousal x group interaction. The hypothesis that differences in subjective ratings between themes would be enhanced by a prior contrasting experience was thus only supported to a very limited degree.

KEY: LOW HIGH

*-e-.--m

HIGH LOW V-4

I I I I I I 1 2 3 4 5 6

THEME NO.

FIG. 2. Mean subjective anxiety ratings for the two groups in experiment 2.

Physiological measures during flooding

A similar repeated measure analysis of variance was performed on the physiological data after any necessary transformations. For heart rate and skin conductance level samples were scored for the third and sixth minute of each theme, and analyses are reported for average values since the results from the two samples were similar. In the case of skin conductance fluctuations, the frequency of zero values made this detailed analysis impossible, and instead the scores were summed across the three replications within arousal conditions.

(a) Heart rate

Analysis of variance of the average heart rate data showed no overall differences between groups, but a number of highly significant within subject effects. These were arousal


(p < O.Ol), replications (p c O.Ol), arousal x groups (p < 0.001) and arousal x groups x

replications (p < 0.001). As can be seen in Fig. 3, the replication effect is clearly one of habituation, since heart rate diminishes with successive themes. Superimposed on this habituation curve is an arousal condition effect, and a more powerful interaction of arousal with group. This resembles a contrast effect, since heart rate in both groups stayed at rather similar levels despite exposure to different themes, but diverged markedly during exposure to contrasting material. The triple interaction (arousal x groups x replications) indicates that habituation rates were influenced differentially by combinations of group (i.e. order) and arousal conditions. Habituation was only clearly apparent in the first block of three themes and was pa~icul~ly rapid when a low arousal theme was presented first; although habituation to high arousal themes was also complete by the end of the second theme.

LOW, pi KEY: - -

HIGH LOW

GROUP I

CROUP 2

I I I I I I I

1 2 3 4 5 6

THEME NO.

FIG. 3. Mean heart rate during the 3rd and 6th min of each theme for the two groups in experiment 2.

(b) Skin conductance

An identical analysis carried out on the skm conductance level data, after transformatron into log micromho units, did not reveal any significant effect other than that due to replications (p < 0.01).

The abbreviated analysis carried out using skin conductance fluctuation frequency, after a logarithmic transformation, did not show any main effect of group or arousal condition, but the arousal x groups interaction was significant (p < 0.05). Unlike the heart rate results, however, this interaction seemed due to a relatively greater response when high arousal themes were presented first.

Treatment effects were examined at the mid-way point, at the end of flooding and after the second behavioural test; in each case by analysis of co-variance using the pre-treatment

596 ANDREWMATHEWS and PJSYLLIS SHAW

score as a co-variate. No significant results were found in the analysis of the phobic attitude scores, but a single highly significant result, a main effect of groups, occurred in the case of the semantic differential scores at the mid-treatment point (p < 0.001). At this stage, Group 1 subjects, who had been exposed to low arousal themes, had gained a more favourable attitude, while Group 2 subjects, who had been exposed to the high arousal themes, showed a deterioration. The two groups converged again after hearing the contrasting themes, so that no differences remained. There were no significant differences between groups in phobic attitude scores despite a trend in favour of Group 2 at post-treatment test (p < 0.10).

Behavioural avoidance test

Hierarchy gain scores and mean anxiety ratings obtained during items which were performed both before and after flooding, were also analysed by analysis of variance pre- treatment, and by analysis of co-variance post-treatment. No significant effects were found in any analysis, so that the results did not support the prediction that contrast effects would produce a greater behavioural change in Group 2 subjects. For comparison purposes mean hierarchy gain scores are shown in Table 1, together with the behavioural gain scores found in the earlier experiment.

DISCUSSION

Hypothesis 1

It had been anticipated that differences in subjective anxiety between groups would be minimal during the first three themes because subjects had no way of making absolute judgements, but rather started at an arbitrary point and thereafter rated in terms of contrast effects. The crucial interaction reflecting contrast effects (arousal x groups) just failed to reach the 5 per cent level, although a strong trend did exist. The first hypothesis concerning contrast effects was therefore not strongly confirmed, although it was far from being ruled out.

Hypothesis 2

The postulate of greater autonomic response during high arousal themes was confirmed by the heart rate data, and a marked decrement across consecutive themes was shown by the significant replication effect in both heart rate and skin conductance level measures. How- ever, the most powerful finding in both heart rate and skin conductance fluctuation data was that of an arousal x groups interaction. There is some contradiction between the two physiological measures, since maximum differences occurred in the second block of themes in the case of skin conductance fluctuations. This may be due to rapid habituation of skin conductance responses, which reduced frequency to near zero rates for most of the time. The form of the heart rate data on the other hand suggests the operation of contrast effects after the crossover point.

Hypothesis 3

This hypothesis was confirmed in the case of the semantic differential, in that a highly significant divergence in attitude had occurred by the mid-way point, when the two groups had been exposed to different sets of themes. Similarly, these changes were completely reversed by the end of flooding, as had been anticipated.


Hypothesis 4

There was no convincing evidence that Group 2 subjects improved more than Group 1 subjects on post-treatment attitudinal, anxiety or behavioural measures. Although trends favoured the hypothesis, no test approached an acceptable level of significance. This suggests that any contrast or recency effects were relatively weak agents for inducing behavioural change.

Although only hypothesis 2 and 3 were confirmed adequately, the general conclusion of the earlier experiment seems strengthened by the second study. Themes which are relatively realistic and reassuring accounts of contact with phobic situations were associated with more beneficial changes in attitude than were fantasy themes evoking relatively higher levels of arousal. That the high arousal themes provoked more anxiety was adequately confirmed for both subjective and autonomic measures.

The finding that not only subjective anxiety, but also ‘attention’ and ‘vividness’ ratings were greater in the high arousal themes was not anticipated, although the ratings were included to check on this possibility. The finding raises the question of how the low themes so effectively reversed prior negative attitudes, if subjects were genuinely less able to attend and involve themselves in them. One possibility is that the change occurred despite this decreased involvement-that is, the low arousal themes would have been even more effective had involvement been as great as in the high arousal themes. Maximum therapeutic effect might therefore be associated with low arousing theme content, presented so as to involve subjects to the same degree as the high arousal themes.

Although not powerful enough to significantly affect outcome measures, there was some evidence that the high-low order was associated with both lower levels and more rapid decrement in anxiety. A similar result has been reported by Lang (1970) deriving from work carried out in his laboratory by Melamed. This study involved hierarchically graded films of snakes presented in a high-low or low-high order, with subjects instructed to just attend, to relax, or to experience the scene and their emotions as fully as possible-the instructions usually given in flooding. Lang concluded from this study that contrast effects resulted in an overall lowering of anxiety, more rapid habituation and consequent lower ratings of fear in a questionnaire, for those subjects who had seen the films in the high-low order. These results are clearly comparable with those of the present experiment, and where differences exist between the studies they are probably attributable to the use of varied instruction sets in the Lang and Melamed experiment.

In conclusion, it seems clear that contrast and persuasion effects can occur in flooding treatment, and may serve to influence subsequent phobic behaviour to a limited extent. Some of the earlier contradictory findings with flooding may be attributable to differential persuasive content or contrast effects inadvertently varied by different experimenters. Additionally, it seems likely that continuing high levels of anxiety during flooding will be associated with poor outcome, although reduced anxiety towards the end of the session may reverse this trend. Studies in which flooding was found to have a therapeutic effect include those in which the experimenters finished with less arousing material (e.g. Kirschner and Hogan, 1966) or continued until anxiety was very much reduced (e.g. Barrett, 1969). Hence, where themes of different anxiety evoking potential are used in a single session it seems advisable to present the most anxiety arousing material first. As Lang (1970) has already suggested in the case of desensitization, this indicates that the common clinical practice of presenting increasingly evocative material as the session progresses should be reversed.

598 ANDREWMATHEWS and PHYLLISSHAW

However, a comparison of ex~riments I and 2 suggests that the best results were obtained with the continuous presentation of theme material in which subjects imagined themselves carrying out counter-phobic behaviour, without ever experiencing excessive anxiety. It may be therefore, that a treatment approach which differs in some respects from both desensitization and ‘implosion’ procedures will prove the most effective imaginal method for rapidly reducing phobic anxiety.

REFERENCES

BANDURA A., BLANCHARD E. B. and RITIZR D. (1969) The relative efficacy of desensitization and modelhng approaches for inducing behavioural, affective and attitudinal changes. J. Person. Sm. Psychof. 13, 173- 199.

BARRETT C. L. (1969) Systematic Desensitization versus Implosive Therapy. f. abnmn. P.~yc/d. 74,581-592. HEL~~N H. (1964) ~~~~ru~~o~~e~e~ Theory. Harper & Row, New York. KIRSCHNER J. H. and HOGAN R. A. (1966) The therapist variable in the implosion of phobias. P~yc~~r~er~~y.

A? Y. 3,102-104. LANG P. J. (1970) Stimulus control, response control and the desensitization of fear. In, Learnina Annro&es

to Therapeuhc Behaviour Change.<Ed. D. J. LEVIS) Aldine, Chicago. _ __

MEALIEA W. L. and NAWAS M. M. (1971) The comparative effectiveness of systematic desensitization and implosive therapy in the treatment of snake phobia. J. Behv. Therapy Exp. Psychiut. 2, 85-94.

emotional arousal and persuasion effects in flooding

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