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The effects of biofeedback and guided imagery on finger temperature
235
BiologicalPsychology 11 (1980) 235-247 North Holland Publishing Company
THE EFFECTS OF BIOFEEDBACK AND GUIDED IMAGERY ON FINGER TEMPERATURE *
C.R. GILLESPIE ** and D.F. PECK Department Accepted
of Psychiatry, University of Edinburgh,
for publication
19 March
Edinburgh,
U.K.
1981
This study was concerned with a comparison of the effects of biofeedback and of imagery on finger temperature increase. Twelve volunteer unpaid adults were randomly allocated to one of two groups: finger temperature biofeedback or guided imagery. All subjects received two baseline and five 15 min treatment sessions, during which stimulus presentation was carefully controlled. The biofeedback group rapidly established a superior ability to increase finger temperature; whereas guided imagery was consistently associated with temperature decrease. Some tentative evidence was produced which questioned the alleged importance of cognitive and interpersonal factors in biofeedback training. Implications for theoretical accounts of the mechanism of finger temperature control (via autogenic training or biofeedback), and for developing effective biofeedback procedures are drawn.
1. Introduction
It is now established that subjects can be trained to regulate skin temperature using biofeedback plus simple instructions (Keefe and Gardner, 1979). There are, however, a number of unresolved experimental issues; for example, how far can subjects regulate skin temperature without recourse to the complex technology of biofeedback and what are the main factors which can influence skin temperature? These issues are of some importance, since fmger temperature increase has been used in the treatment of a number of clinical conditions, in particular migraine headache and Raynaud’s disease (Yates, 1980) and the exploration of factors related to efficient self-regulation may lead to an increase in the clinical efficacy of these procedures. Maslach, Marshall and Zimbardo (1972) presented anecdotal data on three subjects who were able to regulate skin temperature using only hypnotic suggestion. Similarly, Dugan and Sheridan (1976) have shown that changes in hand temperature can be achieved simply through instructions; for example, to imagine immersing hands in warm or iced water. They claimed that the magnitude of tem* Requests for reprints should be sent to D.F. Peck, University Royal Edinburgh Hospital, Edinburgh EHlO SHF, Scotland. ** Now at St. Crispin Hospital, Northampton.
0301-05 1 l/8 l/0000-0000/$02.50
0 1980 North-Holland
Department
of Psychiatry,
236
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perature change was similar to that reported in biofeedback experiments, but no direct comparison was attempted. Herzfeld and Taub (1976) examined whether the presentation of visual imagery and explicit verbal suggestion could enhance biofeedback-produced control of hand temperature. Five subjects were instructed to regulate the temperature of the dominant hand. During half of the biofeedback sessions, subjects were presented with slides and tape recorded commentary with explicit thermal suggestions; during the other sessions, neutral slides and suggestions (i.e., geometric patterns and electronic definitions) were presented. They found that subjects obtained greater temperature changes on ‘suggestion’ than on ‘nonsuggestion’ training days. It should be noted however that no attempt was made to investigate the separate effects of biofeedback and of imagery. Blizard, Cowings and Miller (1975) assessed the effects of autogenic imagery training (in which an important component is suggestions of ‘heaviness’ and ‘warmth’) and of ‘cool’ instructions on a number of autonomic variables. They reported that ‘cool’ suggestions had a significant effect on heart rate, respiration rate and EEG alpha frequency, and that ‘warm’ suggestions produced effects in the opposite direction, but not to a significant degree. However, surprisingly, neither ‘warm’ nor ‘cool’ instructions had a reliable effect on finger temperature. Similar results have been reported by King and Montgomery (1980a) who found in addition that subjects were able to demonstrate finger temperature control with biofeedback only when ‘physical manoeuvres’ (such as tensing muscles and changing respiratory activity) were permitted. There is therefore some inconsistency in the evidence that imagery and suggestion alone can produce skin temperature changes. It is also important to determine whether, if imagery and suggestion can produce temperature effects, these are equal to the effects produced by biofeedback. Keefe (1978) reported that biofeedback and simple ‘thermal suggestions’ produced temperature increases of comparable magnitude. However, a number of design limitations render an unequivocal interpretation of his results impossible. For example, the groups were presented with stimuli of unequal salience; the training period was only 10 min per session; only a 10 min adaptation period was used, and no criteria in relation to determination of temperature stability point were reported. In a study using female patients suffering from Raynaud’s disease, Surwit, Pilon and Fenton (1978) found that temperature feedback had no incremental value over autogenic training alone, again suggesting that instructions and suggestions may produce equal effects to those produced by biofeedback. However, the autogenic training procedure is a complex treatment package incorporating suggestions of heaviness and warmth, meditative exercises, ‘passive concentration’ and other ingredients (Schultz and Luthe, 1969). ‘Thus, in Surwit et al.‘s (1978) study, the precise role of imagery cannot be elucidated. The concept of imagery plays a prominent role in a number of theoretical accounts of biofeedback mechanisms. Brener (1974), for example, put forward that a ‘response image’ enhances the development of a link between the exteroceptive feedback stimulus and the interoceptive feedback from the target physiological
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response, thereby implementing or increasing awareness of the latter and facilitating self-regulation. Schwartz (197.5) has expressed a similar view. Despite this theoretical prominence, however, experimental studies of imagery in relation to biofeedback are quite rare and the few results reported so far have thrown little light on the issue. Generally, however, it would appear that the role of imagery in biofeedback is not a crucial one (Yates, 1980) but more research is required before any firm conclusions can be drawn. An additional important question, which has again received little attention, is the influence of stimulus presentation on finger temperature. Plutchik (1956) reviewed the earlier evidence relating to the effects of a variety of stimuli and emotional states on skin temperature, and concluded that under a wide range of conditions, stimulation typically produced a decrease in temperature; in particular, it seemed that large magnitude decreases were associated with attempts at solving difficult problems. Cook (1974) examined the effects of stimulus presentation and task-related factors on the peripheral vascular system; generally, such factors produce a vasoconstrictive response in the finger. Although the relationship between peripheral vascular changes and skin temperature is a highly complex one (King and Montgomery, 1980b) and a one-to-one relationship between them can certainly not be assumed, it may reasonably be concluded that such factors would also affect finger temperature. More recently, Cook, Gerkovich, Graham, Cohen and Anderson (1979) looked in some detail at determinants of skin temperature change. They reported that ‘cognitive stimuli’ (e.g., mental arithmetic) produced greater effects on finger temperature than did such ‘physical stimuli’ as the application of heat and cold, and isometric excercises. Of particular interest for the present study was their finding that task instructions generally reduced skin temperature. They recommended the use of ‘dynamic’, rather than ‘resting’, baselines, against which to compare experimental change. It would appear, therefore, that in any comparative study, steps must be taken to ensure that the ‘arousing’ properties of the stimuli presented are comparable. The present study was designed to compare directly the effects of a guided imagery procedure, and of biofeedback, on finger temperature increase. It was decided to use the guided imagery, since this was the procedure reported by Herzfeld and Taub (1976); however, they examined the effects of combining biofeedback and imagery, whereas the present study was designed to examine the effects separately. In addition, it was considered that the content of the slides and recorded material which accompanied the imagery would serve to augment any effects. Temperature increase was adopted as the target response since this is the typical target in clinical applications (Yates, 1980). Particular care was taken to control for the effects of stimulus presentation, by making baseline conditions, and experimental conditions in the two groups, as close as possible.
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2. Method 2.1. Subjects Twelve volunteer unpaid subjects, six male and six female, participated in the study; they were recruited from amongst the staff and trainees of a psychiatric hospital and from a college of education. All were naive regarding biofeedback; the mean age was 26 years. 2.2. Apparatus
A Comark Electronic Thermometer (type 1608 NiCr/NiAl) was used to measure temperature. With this device, a 1 V output corresponds to a 10°C full-scale needle deflection. This output was linked to a Weston Schlumberger Autoranging Digital Multimeter, which provided digital feedback of finger temperature to l/lOO”C. Temperature changes were recorded on a Washington Oscillograph 400 MD/2. A Singer Caramate rotary slide projector with autochange and audiotrack facilities was used for stimulus presentation. The visual material comprised 30 slides, 10 of geometrical designs, 10 of scenes depicting temperature-linked scenes, and 10 of clear glass. The auditory material comprised 10 short selections from a psychology textbook and 10 verbal commentaries related to the temperature-linked slides. 2.3. Procedure Subjects were randomly assigned to one of two treatment groups: biofeedback (treatment A) or guided imagery (treatment B); each group contained three males and three females. They were told that the study was ‘investigating the ways in which people attain self-control of their hand temperature’. Subjects agreed to attend the laboratory at the same hour for each session; this was intended to control for 24 h temperature rhythm. All subjects were then given two baseline sessions, each of a different type, in random order. At the beginning of each baseline and each treatment session, the thermocouple probe was attached to the central whorl print of the middle finger of the dominant hand and connected to the Comark Thermometer. The probe lead was secured with micropore surgical tape and the probe was kept in contact with the skin using a Scholl adhesive felt corn pad. The corn pad centre hole was placed directly over the tip of the thermocouple protecting it from incidental draughts and permitting moisture to evaporate. To summarise the design: all subjects received both Baseline 1 and Baseline 2 in a randomly determined order. Subsequently subjects were randomly allocated to treatment A (five sessions of biofeedback) or to treatment B (five sessions of guided imagery). Finger temperature was monitored throughout all baseline and treatment sessions.
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2.4. Baseline I Subjects instructions:
were seated in a comfortable
armchair and given the following typed
During this session, please try and relax but remain awake. Throughout the session you are requested to be aware of the numbers flashing on the illuminated meter. During fixed intervals the room will be in darkness for a few seconds. Continue to relax and await the next exposure of the illuminated meter. Try not to move; just remain relaxed and awake. Do you have any questions?
Temperature was recorded on the Washington pen recorder, and was monitored until the stability criterion had been achieved (no more than 0.2”C change over four consecutive 1 min periods with a minimum of 10 min and a maximum of 20 min). Subjects were given ten 80 set trials during which slowly changing, meaningless numbers were shown on the liquid crystal display of the Multimeter, which was illuminated by light from the Singer Caramate projected through clear glass slides. The light was turned off automatically after each trial for 10 set (intertrial interval), leaving the room in darkness for that period. This procedure was very similar to that used in treatment A (described below). 2.5. Baseline 2 Subjects were seated, thermocouple probes were attached, and the stability criterion was achieved as described above. Subjects were given ten 80 set trials consisting of the presentation of slides of geometrical patterns and tape recorded verbal material from a textbook on sensory discrimination theory. The intertrial interval was again 10 set during which the room was in darkness. Temperature was recorded throughout the session. Typed instructions were given as follows: During this test session, please try and relax and remain awake. Throughout the session you are requested to be aware of the visual material displayed on the screen and the verbal information that will precede each slide. You are not required to learn or understand any material, visual or verbal. During fixed intervals, the room will be in darkness for a few seconds. Continue to relax and await the next sequence. Try not to move, just remain relaxed and awake. Do you have any questions?
This procedure was very similar to that used in treatment B (described below). Furthermore baselines 1 and 2 were very similar to each other in respect of length, number of trials, concentration required and overall structure. 2.6. Treatment A This treatment was procedurally very similar to baseline 1, differing in that: (1) The Multimeter was connected to the output of the Comark thermometer,
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the subsequent display giving digital feedback of finger temperature and the Multimeter display was again illuminated by light from the Caramate projected through the clear glass slides. (2) Subjects rated before and after each session (on a l-7 scale) the following variables which, according to the published literature, summarised in Hume (1977), could be related to temperature control: relaxed vs. tense; cheerful vs. depressed; confidence in ability vs. unsure of ability to do task; credible vs. not credible procedure; tired vs. energetic; interesting vs. boring task; like vs. unlike normal self; complex vs. simple task; friendly vs. distant experimenter; and remote vs. sociable towards experimenter. Each subject also completed Rotter’s (1966) internal/ external locus of control scale. (3) The typed instructions were as follows: During this session you are required to raise the reading on the illuminated meter, which is a measure of your finger tip temperature. Use the feedback from the meter to increase your successful efforts. People devise their own strategies to do this, often using some form of mental control. Try and remain still throughout but do not concentrate too hard. During fixed intervals the room will be in darkness for a few seconds. As soon as the meter is illuminated renew your efforts to increase its reading. Do you have any questions?
Following stabilisation, the sessions lasted for 1.5 min and comprised ten 80 set trials with 10 set intertrial intervals. Subjects were praised for their performance at the end of each session. Each subject attended for five sessions. 2.7. Treatment B Six subjects received treatment B, which was procedurally very similar to baseline 2 differing in that: (1) Subjects were presented via the Singer Caramate with slides accompanied by related tape-recorded material designed to evoke images of temperature increase (e.g., slide of a coal-fire, accompanied by the following recording: ‘You are sitting close to the fireplace. Feel the warmth of the flames on you hands. The heat on the front of your body is so intense.‘). (2) The self report measures as in treatment A were completed before and after each of the five treatment sessions. Subjects also completed the locus of control scale. (3) Subjects were given the following instructions: During this session you are requested to raise your finger tip temperature. In order to help you do this, you will receive taped instructions prior to seeing a slide of a scene inviting you to share the high temperatures you would experience if photographed in the scene. Try and remain still throughout but do not concentrate too hard. During fixed intervals the room will be in darkness for a few seconds. Await instructions for your next invitation. Use your imagination as fully as possible to enter each scene. Do you have any questions?
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Each session lasted for 15 min and comprised ten 80 set trials, with an intertrial interval of 10 sec. The 10 slides were each shown once at every session. Subjects were praised for their performance at the end of each session. All sessions took place in a quiet, dimly lit room, with temperature constant at 25 f 1°C. Treatments A and B were therefore similar in the following respects: length and number of sessions, number of trials, number of slides and projection equipment used; the only major difference was the use of tape-recorded material in treatment B. The stimulus arousal properties of the treatments were therefore very similar. Similarly, baselines 1 and 2 were very similar to treatments A and B respectively. The scoring system (described below) also served to minimise any systematic differences between the treatments. Thus factors other than the main independent variable (biofeedback vs. guided imagery) that could be responsible for any temperature changes were controlled. 2.8. Scoring system The method of calculating temperature change in all sessions was based on that described by Taub and Emurian (1976). Temperature at the end of each trial was deducted from the stability point temperature for that session. These scores were then grouped as follows: ‘Early session’ trials (1, 2 and 3); ‘mid session’ trials (4,5, 6 and 7): and ‘end session’ trials (8,9 and 10) and the mean for each group of trials was calculated. Thus each baseline session and each training session generated three mean change scores. Finally, the baseline mean changes were deducted from the training mean changes; thus ‘early session’ baseline changes were deducted from ‘early session’ training changes; ‘mid session’ baseline changes were deducted from ‘mid session’ training changes; and ‘end session’ baseline changes were deducted from ‘end session’ training changes. The resulting performance scores were designated Ta, Tb and Tc respectively. Treatment A was compared with baseline 1; treatment B with baseline 2. This ‘ipsitised’ method controls for spontaneous temperature changes; only changes over and above those occurring during comparable baseline conditions are considered to constitute a valid increase.
3. Results 3.1. Biofeedback
vs. guided imagery
The Tc scores (as the ‘end session’ scores, being the most crucial measure of the acquisition of control) are displayed graphically in fig. 1, for both groups. The results were analysed by the Mann-Whitney U test; the differences between the groups are significant (U= 0, p =
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10
FEEDBACK
0
Tc “C
IMAGERY
s 10
g:
-5 -
-10 -
-15 1
2
3
k
;
SESSIONS
Fig. 1. Mean changes imagery groups.
in finger
temperature
(Tc X 10) over sessions for the biofeedback
and the
It will be noted that, after ipsitisation, the biofeedback group produced a mean increase in all sessions except the first; whereas the imagery group produced a mean decrease in all sessions. However, the magnitude of the changes was quite small, the overall mean Tc increase for the biofeedback group being only +0.22”C; and the mean decrease for the imagery group was -0.6O”C. The differences between the groups in the early part of the sessions (Ta scores) were not significant (U= 5, n.s.); the mid-session differences (Tb scores) were just significant (U = 2, p =
4. Discussion Self-regulation of finger temperature by biofeedback was rapidly established, and the biofeedback group’s performance remained higher than that of the guided imagery group throughout all sessions. The guided imagery procedure was consistently associated with temperature decrease, perhaps reflecting the downward influ-
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ence of stimulus presentation on finger temperature (Cook et al., 1979), an influence which could not be effectively counteracted by imagery, but which could by biofeedback. This finding of the weak, or negative, influence of imagery is consistent with the bulk of the evidence from other biofeedback studies, including those concerned with blood volume pulse, electrodermal activity, and muscle activity (Yates, 1980). This would suggest that in those studies which have reported a finger temperature increase as a result of autogenic and related training procedures (e.g., Surwit et al., 1978) the effect of imagery per se within the total treatment package may possibly have been minimal, or even negative. However, the precise function of imagery within complex treatment packages can only be fully clarified by studies designed to separate out the effects of component parts, singly and in combination. There remains the possibility that, although a negative effect may result from imagery alone, a positive effect may result from the interaction between imagery and other procedures within autogenic and relaxation treatments. Certainly it would be premature to draw conclusions from this study concerning the therapeutic efficacy of relaxation and autogenic training as a whole; there is much evidence attesting to their clinical utility in problems such as headache and Raynaud’s disease, at least in the short-term (King, 1980). A further implication is that subjects learning to control skin temperature may develop the skill more efficiently, if left to devise their own strategies rather than instructed to use imagery. Evidence has now accumulated indicating that a wide range of stimuli (including instructions) may produce a decrease in finger temperature, a response clearly incompatible with the goal of clinical temperature control studies (that is, temperature increase). One interesting implication of this is that small changes (or even no change) may still demonstrate the acquisition of temperature control, since under comparable experimental conditions, but without feedback, temperature would probably decrease. Despite its fundamental importance, however, this topic has received little direct attention, nor has its significance been generally recognised. An exception is the study of Surwit, Shapiro and Feld (1976). They suggested that this decrement in temperature, and the common finding that temperature decrease is easier to achieve than increase, may be accounted for by reference to the concept of the Orienting Reflex (OR). The OR refers to widespread psychophysiological reactions, which occur in response to the presentation of stimuli, of which an important component is hand vasoconstriction. It has been most completely described by Sokolov (1963). However, it should be noted that the OR occurs in response to discrete, novel stimuli, and the relevance of the concept of OR to the kinds of. stimuli and instructions presented in biofeedback and imagery studies is therefore in doubt. Although recent extensions of OR theory (e.g. Siddle, O’Gorman and Wood, 1979) wherein such stimulus factors as ‘significance’ may partly determine the strength of the OR, suggest a possible role for the OR in accounting for temperature decrease, this is in need of further clarification. King and Montgomery (1980a) reported that, only when ‘physical manoeuvres’ were permitted, were subjects able to demonstrate temperature increase. It is pas-
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sible, therefore, that some of the increases found in the present study could have resulted from such an artifact. This is unlikely, however, for two main reasons: first, such manoeuvres as hand movements or tensing arm muscles produce a marked rapid fluctuation on the pen recording, and inspection of the recordings indicated that such fluctuations were rare and not systematically related to temperature change in any of the subjects; second, reliable differences were found between the two groups, and it would be difficult to explain why biofeedback subjects should be more prone to use manoeuvres than imagery subjects. The standard deviations reported in table 1 reveal a high degree of variability within both groups. One subject in the biofeedback group was consistently unable to demonstrate finger temperature increase, and there was marked variation from session to session and within each session for all subjects. Thus, although the changes in finger temperature were sufficient to produce significant differences between the groups, individual subjects were unable to demonstrate temperature self-regulation reliably. It is also of interest to note that the skill of temperature self-regulation was acquired within five 15 min sessions, consistent with the claim of Taub and Emurian (1976). The low level of temperature change obtained with biofeedback in this study is consistent with a number of recent reports (e.g., Surwit et al., 1976) and has been recently documented by King and Montgomery (1980b). In the present study the experimental conditions were not conducive to producing large temperature change because, as already suggested, the stimuli presented may have produced a tendency towards temperature decrease, against which the influence of biofeedback would have to compete. Also, three male subjects in the biofeedback group had a basal skin temperature of approximately 35°C which is close to a physiological ceiling. Felder, Russ, Montgomery and Horwitz (1954) have shown that once skin temperature reaches 34°C further small increases in skin temperature require considerable increases in blood flow. Thus subjects with high basal skin temperatures will be less able to produce large-scale increases. Surwit et al. (1976) examined the influence of basal finger temperature on acquisition of control by setting room temperature at 225°C for some subjects or 19.5”C for others and reported that the lower temperature was not associated with improved performance, which might have been expected if a ‘ceiling’ effect was an important determinant of the acquisition of control. However, ambient temperature is only one of several factors which determine skin temperature (Dubois, 1941). The results of Surwit et al. (1976) may, therefore, not be generally applicable to situations where elevated basal skin temperature is due to other factors. In the present study, it should be emphasised that ambient temperature was kept constant, yet high basal temperatures were still obtained for these three subjects (35°C). High basal finger temperature may still, therefore, account in part for the small magnitude of the temperature changes obtained in this study. The superiority of the biofeedback group may have been more clear-cut if subjects had been allocated to the treatment groups partly on the basis of initial stabil-
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ity point; this should be taken into account in future studies. In this study, little support was found for the alleged role of cognitive and interpersonal processes in temperature self-regulation. Ratings of task credibility, confidence in task, friendliness of experimenter and so on, were not significantly different between the groups, yet systematic differences in performance emerged. It cannot of course be argued from this that these variables play no role in self-regulatory tasks; rather that such variables are not in themselves sufficient to account for the temperature changes. The precise role of cognitive and interpersonal processes can best be elucidated by systematically varying these factors within the same treatment process. A word of caution should be sounded concerning the ‘ipsitisation’ method of scoring temperature changes used in this study. It will be remembered that ‘spontaneous’ changes during baseline were deducted from changes obtained during training; therefore if temperature decreased during baseline, the apparent magnitude of the temperature increase during training would be inflated. Although this cannot account for the systematic differences reported in this study, since temperatures in baselines 1 and 2 tended to change in both directions, care must be taken in the interpretation of results from studies using this scoring method. Finally, it is recommended that future research studies in this area should pay due attention to the potential contamination effect of stimulus presentation on finger temperature, by instituting control procedures similar to those in the present study. The main conclusions of the study are that guided imagery as utilised in this experiment does not appear to be an effective procedure for producing finger temperature increases; increases were, however, obtained by a biofeedback group, although they were of low magnitude and somewhat variable. Also some tentative evidence has suggested that cognitive and interpersonal processes cannot in themselves be regarded as sufficient explanations for changes occurring with finger temperature biofeedback.
References Blizard, D., Cowings, P. and Miller, N.E. (1975). Visceral responses to opposite types ofautogenie-training imagery. Biological Psychology, 3,49-55. Brener, J. (1974). A general model of voluntary control applied to the phenomena of learned cardiovascular control. In: Obrist, P.A. Black, A.H. Brener, J. and DiCara, L.V. (Eds.). Cardiovascular Psychophysiology: Current Issues in Response Mechanisms, Biofeedback and Methodology. Aldine: Chicago. Cook, M.R. (1974). Psychophysiology of peripheral vascular changes. In: Obrist, P.A., Black, A.H., Brener, J. and DiCara, L.V. (Eds.). Cardiovascular Psychophysiology: Current Issues in Response Mechanisms, Biofeedback and Methodology. Aldine: Chicago. Cook, M.R., Gerkovich, M.M., Graham, C., Cohen, M.D. and Anderson, F.I. (1979). Effects of cognitive and physical stimuli on finger temperature. Psychophysiology, 16, 176-177 (abstract).
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Dubois, E.F. (1941). The temperature of the human body in health and disease. In: American Institute of Physics (Ed.). Temperature: Its Measurement and Control in Science and Industry. Reinholt: New York. Dugan, M. and Sheridan, C. (1976). Effects of instructed imagery on temperature of hands. Perceptual and hlotor Skills, 42, 14. Felder, D., Russ, E., Montgomery, H. and Horwitz, 0. (1954). Relationship in the toe of skin surface temperature to mean blood flow measured with a plethysmogram. Clinical Science, 13, 251-257. Herzfeld, G.M. and Taub, E. (1976). Suggestion as an aid to self-regulation of hand temperature. Paper presented at a meeting of the Biofeedback Research Society, Colorado Springs. Hume, W.I. (1977). Biofeedback, Vol. 2. Churchill Livingston: Edinburgh. Keefe, F.J. (1978). Biofeedback vs. instructional control of skin temperature. Journal of Behavioral Medicine, 1, 3833390. Keefe, F.J. and Gardner, ET. (1979). Learned control of skin temperature: Effects of short and long-term biofeedback training. Behavior Therapy, 10, 2022210. King, N.J. (1980). The therapeutic utility of abbreviated progressive relaxation: A critical review with implications for practice. In: Hersen, M., Eisler, R. and Miller, P.M. (Eds). Progress in Behavior Modification, Vol. 10, Academic Press: New York. King, N.J. and Montgomery, R.B. (1980a). A component analysis of biofeedback induced selfcontrol of peripheral (linger) temperature. Biological Psychology 10, 1399152. King, N.J. and Montgomery, R.B. (1980b). Biofeedback-induced control of human peripheral temperature: A critical review of the literature. Psychological Bulletin, 88, 738-752. Maslach, C., Marshall, G. and Zimbardo, P.G. (1972). Hypnotic control of peripheral skin temperature: A case report. Psychophysiology, 9,600-605. Plutchik, R. (1956). The psychophysiology of skin temperature: A critical review. Journal of General Psychology, 55, 249-268. Rotter, J.B. (1966). Generalized expectancies for internal versus external control of reinforcement. Psychological Monographs, 80 (1 Whole no. 609). Schultz, J.H. and Luthe, W. (1969). Autogenic Therapy. Grune and Stratton: New York. Schwartz, G.E. (1975). Biofeedback, self-regulation, and the patterning of physiological processes. American Scientist, 63, 3 144324. Siddle, D.A., O’Gorman, J.G. and Wood, L. (1979). Effects of electrodermal lability and stimulus significance on electrodermal response amplitude to stimulus change. Psychophysiology, 16,520-521. Sokolov, E.N. (1963). Perception and the Conditioned Reflex. Macmillan: New York. Surwit, R.S., Pilon, R. and Fenton, C. (1978). Behavioral treatment of Raynaud’s Disease. Journal of Behavioral Medicine, 1, 323-336. Surwit, R.S., Shapiro, D. and Feld, J.L. (1976). Digital temperature autoregulation and associated cardio-vascular changes. Psychophysiology, 13, 242-248. Taub, E. and Emurian, C.S. (1976). Feedback aided self-regulation of skin temperature with a single feedback locus. 1. Acquisition and reversal training. Biofeedback and Self-Regulation, 1,147-168. Yates, A.J. (1980). Biofeedback and the Modification of Behavior. Plenum: New York.
BiologicalPsychology 11 (1980) 235-247 North Holland Publishing Company
THE EFFECTS OF BIOFEEDBACK AND GUIDED IMAGERY ON FINGER TEMPERATURE *
C.R. GILLESPIE ** and D.F. PECK Department Accepted
of Psychiatry, University of Edinburgh,
for publication
19 March
Edinburgh,
U.K.
1981
This study was concerned with a comparison of the effects of biofeedback and of imagery on finger temperature increase. Twelve volunteer unpaid adults were randomly allocated to one of two groups: finger temperature biofeedback or guided imagery. All subjects received two baseline and five 15 min treatment sessions, during which stimulus presentation was carefully controlled. The biofeedback group rapidly established a superior ability to increase finger temperature; whereas guided imagery was consistently associated with temperature decrease. Some tentative evidence was produced which questioned the alleged importance of cognitive and interpersonal factors in biofeedback training. Implications for theoretical accounts of the mechanism of finger temperature control (via autogenic training or biofeedback), and for developing effective biofeedback procedures are drawn.
1. Introduction
It is now established that subjects can be trained to regulate skin temperature using biofeedback plus simple instructions (Keefe and Gardner, 1979). There are, however, a number of unresolved experimental issues; for example, how far can subjects regulate skin temperature without recourse to the complex technology of biofeedback and what are the main factors which can influence skin temperature? These issues are of some importance, since fmger temperature increase has been used in the treatment of a number of clinical conditions, in particular migraine headache and Raynaud’s disease (Yates, 1980) and the exploration of factors related to efficient self-regulation may lead to an increase in the clinical efficacy of these procedures. Maslach, Marshall and Zimbardo (1972) presented anecdotal data on three subjects who were able to regulate skin temperature using only hypnotic suggestion. Similarly, Dugan and Sheridan (1976) have shown that changes in hand temperature can be achieved simply through instructions; for example, to imagine immersing hands in warm or iced water. They claimed that the magnitude of tem* Requests for reprints should be sent to D.F. Peck, University Royal Edinburgh Hospital, Edinburgh EHlO SHF, Scotland. ** Now at St. Crispin Hospital, Northampton.
0301-05 1 l/8 l/0000-0000/$02.50
0 1980 North-Holland
Department
of Psychiatry,
236
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perature change was similar to that reported in biofeedback experiments, but no direct comparison was attempted. Herzfeld and Taub (1976) examined whether the presentation of visual imagery and explicit verbal suggestion could enhance biofeedback-produced control of hand temperature. Five subjects were instructed to regulate the temperature of the dominant hand. During half of the biofeedback sessions, subjects were presented with slides and tape recorded commentary with explicit thermal suggestions; during the other sessions, neutral slides and suggestions (i.e., geometric patterns and electronic definitions) were presented. They found that subjects obtained greater temperature changes on ‘suggestion’ than on ‘nonsuggestion’ training days. It should be noted however that no attempt was made to investigate the separate effects of biofeedback and of imagery. Blizard, Cowings and Miller (1975) assessed the effects of autogenic imagery training (in which an important component is suggestions of ‘heaviness’ and ‘warmth’) and of ‘cool’ instructions on a number of autonomic variables. They reported that ‘cool’ suggestions had a significant effect on heart rate, respiration rate and EEG alpha frequency, and that ‘warm’ suggestions produced effects in the opposite direction, but not to a significant degree. However, surprisingly, neither ‘warm’ nor ‘cool’ instructions had a reliable effect on finger temperature. Similar results have been reported by King and Montgomery (1980a) who found in addition that subjects were able to demonstrate finger temperature control with biofeedback only when ‘physical manoeuvres’ (such as tensing muscles and changing respiratory activity) were permitted. There is therefore some inconsistency in the evidence that imagery and suggestion alone can produce skin temperature changes. It is also important to determine whether, if imagery and suggestion can produce temperature effects, these are equal to the effects produced by biofeedback. Keefe (1978) reported that biofeedback and simple ‘thermal suggestions’ produced temperature increases of comparable magnitude. However, a number of design limitations render an unequivocal interpretation of his results impossible. For example, the groups were presented with stimuli of unequal salience; the training period was only 10 min per session; only a 10 min adaptation period was used, and no criteria in relation to determination of temperature stability point were reported. In a study using female patients suffering from Raynaud’s disease, Surwit, Pilon and Fenton (1978) found that temperature feedback had no incremental value over autogenic training alone, again suggesting that instructions and suggestions may produce equal effects to those produced by biofeedback. However, the autogenic training procedure is a complex treatment package incorporating suggestions of heaviness and warmth, meditative exercises, ‘passive concentration’ and other ingredients (Schultz and Luthe, 1969). ‘Thus, in Surwit et al.‘s (1978) study, the precise role of imagery cannot be elucidated. The concept of imagery plays a prominent role in a number of theoretical accounts of biofeedback mechanisms. Brener (1974), for example, put forward that a ‘response image’ enhances the development of a link between the exteroceptive feedback stimulus and the interoceptive feedback from the target physiological
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response, thereby implementing or increasing awareness of the latter and facilitating self-regulation. Schwartz (197.5) has expressed a similar view. Despite this theoretical prominence, however, experimental studies of imagery in relation to biofeedback are quite rare and the few results reported so far have thrown little light on the issue. Generally, however, it would appear that the role of imagery in biofeedback is not a crucial one (Yates, 1980) but more research is required before any firm conclusions can be drawn. An additional important question, which has again received little attention, is the influence of stimulus presentation on finger temperature. Plutchik (1956) reviewed the earlier evidence relating to the effects of a variety of stimuli and emotional states on skin temperature, and concluded that under a wide range of conditions, stimulation typically produced a decrease in temperature; in particular, it seemed that large magnitude decreases were associated with attempts at solving difficult problems. Cook (1974) examined the effects of stimulus presentation and task-related factors on the peripheral vascular system; generally, such factors produce a vasoconstrictive response in the finger. Although the relationship between peripheral vascular changes and skin temperature is a highly complex one (King and Montgomery, 1980b) and a one-to-one relationship between them can certainly not be assumed, it may reasonably be concluded that such factors would also affect finger temperature. More recently, Cook, Gerkovich, Graham, Cohen and Anderson (1979) looked in some detail at determinants of skin temperature change. They reported that ‘cognitive stimuli’ (e.g., mental arithmetic) produced greater effects on finger temperature than did such ‘physical stimuli’ as the application of heat and cold, and isometric excercises. Of particular interest for the present study was their finding that task instructions generally reduced skin temperature. They recommended the use of ‘dynamic’, rather than ‘resting’, baselines, against which to compare experimental change. It would appear, therefore, that in any comparative study, steps must be taken to ensure that the ‘arousing’ properties of the stimuli presented are comparable. The present study was designed to compare directly the effects of a guided imagery procedure, and of biofeedback, on finger temperature increase. It was decided to use the guided imagery, since this was the procedure reported by Herzfeld and Taub (1976); however, they examined the effects of combining biofeedback and imagery, whereas the present study was designed to examine the effects separately. In addition, it was considered that the content of the slides and recorded material which accompanied the imagery would serve to augment any effects. Temperature increase was adopted as the target response since this is the typical target in clinical applications (Yates, 1980). Particular care was taken to control for the effects of stimulus presentation, by making baseline conditions, and experimental conditions in the two groups, as close as possible.
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2. Method 2.1. Subjects Twelve volunteer unpaid subjects, six male and six female, participated in the study; they were recruited from amongst the staff and trainees of a psychiatric hospital and from a college of education. All were naive regarding biofeedback; the mean age was 26 years. 2.2. Apparatus
A Comark Electronic Thermometer (type 1608 NiCr/NiAl) was used to measure temperature. With this device, a 1 V output corresponds to a 10°C full-scale needle deflection. This output was linked to a Weston Schlumberger Autoranging Digital Multimeter, which provided digital feedback of finger temperature to l/lOO”C. Temperature changes were recorded on a Washington Oscillograph 400 MD/2. A Singer Caramate rotary slide projector with autochange and audiotrack facilities was used for stimulus presentation. The visual material comprised 30 slides, 10 of geometrical designs, 10 of scenes depicting temperature-linked scenes, and 10 of clear glass. The auditory material comprised 10 short selections from a psychology textbook and 10 verbal commentaries related to the temperature-linked slides. 2.3. Procedure Subjects were randomly assigned to one of two treatment groups: biofeedback (treatment A) or guided imagery (treatment B); each group contained three males and three females. They were told that the study was ‘investigating the ways in which people attain self-control of their hand temperature’. Subjects agreed to attend the laboratory at the same hour for each session; this was intended to control for 24 h temperature rhythm. All subjects were then given two baseline sessions, each of a different type, in random order. At the beginning of each baseline and each treatment session, the thermocouple probe was attached to the central whorl print of the middle finger of the dominant hand and connected to the Comark Thermometer. The probe lead was secured with micropore surgical tape and the probe was kept in contact with the skin using a Scholl adhesive felt corn pad. The corn pad centre hole was placed directly over the tip of the thermocouple protecting it from incidental draughts and permitting moisture to evaporate. To summarise the design: all subjects received both Baseline 1 and Baseline 2 in a randomly determined order. Subsequently subjects were randomly allocated to treatment A (five sessions of biofeedback) or to treatment B (five sessions of guided imagery). Finger temperature was monitored throughout all baseline and treatment sessions.
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2.4. Baseline I Subjects instructions:
were seated in a comfortable
armchair and given the following typed
During this session, please try and relax but remain awake. Throughout the session you are requested to be aware of the numbers flashing on the illuminated meter. During fixed intervals the room will be in darkness for a few seconds. Continue to relax and await the next exposure of the illuminated meter. Try not to move; just remain relaxed and awake. Do you have any questions?
Temperature was recorded on the Washington pen recorder, and was monitored until the stability criterion had been achieved (no more than 0.2”C change over four consecutive 1 min periods with a minimum of 10 min and a maximum of 20 min). Subjects were given ten 80 set trials during which slowly changing, meaningless numbers were shown on the liquid crystal display of the Multimeter, which was illuminated by light from the Singer Caramate projected through clear glass slides. The light was turned off automatically after each trial for 10 set (intertrial interval), leaving the room in darkness for that period. This procedure was very similar to that used in treatment A (described below). 2.5. Baseline 2 Subjects were seated, thermocouple probes were attached, and the stability criterion was achieved as described above. Subjects were given ten 80 set trials consisting of the presentation of slides of geometrical patterns and tape recorded verbal material from a textbook on sensory discrimination theory. The intertrial interval was again 10 set during which the room was in darkness. Temperature was recorded throughout the session. Typed instructions were given as follows: During this test session, please try and relax and remain awake. Throughout the session you are requested to be aware of the visual material displayed on the screen and the verbal information that will precede each slide. You are not required to learn or understand any material, visual or verbal. During fixed intervals, the room will be in darkness for a few seconds. Continue to relax and await the next sequence. Try not to move, just remain relaxed and awake. Do you have any questions?
This procedure was very similar to that used in treatment B (described below). Furthermore baselines 1 and 2 were very similar to each other in respect of length, number of trials, concentration required and overall structure. 2.6. Treatment A This treatment was procedurally very similar to baseline 1, differing in that: (1) The Multimeter was connected to the output of the Comark thermometer,
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the subsequent display giving digital feedback of finger temperature and the Multimeter display was again illuminated by light from the Caramate projected through the clear glass slides. (2) Subjects rated before and after each session (on a l-7 scale) the following variables which, according to the published literature, summarised in Hume (1977), could be related to temperature control: relaxed vs. tense; cheerful vs. depressed; confidence in ability vs. unsure of ability to do task; credible vs. not credible procedure; tired vs. energetic; interesting vs. boring task; like vs. unlike normal self; complex vs. simple task; friendly vs. distant experimenter; and remote vs. sociable towards experimenter. Each subject also completed Rotter’s (1966) internal/ external locus of control scale. (3) The typed instructions were as follows: During this session you are required to raise the reading on the illuminated meter, which is a measure of your finger tip temperature. Use the feedback from the meter to increase your successful efforts. People devise their own strategies to do this, often using some form of mental control. Try and remain still throughout but do not concentrate too hard. During fixed intervals the room will be in darkness for a few seconds. As soon as the meter is illuminated renew your efforts to increase its reading. Do you have any questions?
Following stabilisation, the sessions lasted for 1.5 min and comprised ten 80 set trials with 10 set intertrial intervals. Subjects were praised for their performance at the end of each session. Each subject attended for five sessions. 2.7. Treatment B Six subjects received treatment B, which was procedurally very similar to baseline 2 differing in that: (1) Subjects were presented via the Singer Caramate with slides accompanied by related tape-recorded material designed to evoke images of temperature increase (e.g., slide of a coal-fire, accompanied by the following recording: ‘You are sitting close to the fireplace. Feel the warmth of the flames on you hands. The heat on the front of your body is so intense.‘). (2) The self report measures as in treatment A were completed before and after each of the five treatment sessions. Subjects also completed the locus of control scale. (3) Subjects were given the following instructions: During this session you are requested to raise your finger tip temperature. In order to help you do this, you will receive taped instructions prior to seeing a slide of a scene inviting you to share the high temperatures you would experience if photographed in the scene. Try and remain still throughout but do not concentrate too hard. During fixed intervals the room will be in darkness for a few seconds. Await instructions for your next invitation. Use your imagination as fully as possible to enter each scene. Do you have any questions?
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Each session lasted for 15 min and comprised ten 80 set trials, with an intertrial interval of 10 sec. The 10 slides were each shown once at every session. Subjects were praised for their performance at the end of each session. All sessions took place in a quiet, dimly lit room, with temperature constant at 25 f 1°C. Treatments A and B were therefore similar in the following respects: length and number of sessions, number of trials, number of slides and projection equipment used; the only major difference was the use of tape-recorded material in treatment B. The stimulus arousal properties of the treatments were therefore very similar. Similarly, baselines 1 and 2 were very similar to treatments A and B respectively. The scoring system (described below) also served to minimise any systematic differences between the treatments. Thus factors other than the main independent variable (biofeedback vs. guided imagery) that could be responsible for any temperature changes were controlled. 2.8. Scoring system The method of calculating temperature change in all sessions was based on that described by Taub and Emurian (1976). Temperature at the end of each trial was deducted from the stability point temperature for that session. These scores were then grouped as follows: ‘Early session’ trials (1, 2 and 3); ‘mid session’ trials (4,5, 6 and 7): and ‘end session’ trials (8,9 and 10) and the mean for each group of trials was calculated. Thus each baseline session and each training session generated three mean change scores. Finally, the baseline mean changes were deducted from the training mean changes; thus ‘early session’ baseline changes were deducted from ‘early session’ training changes; ‘mid session’ baseline changes were deducted from ‘mid session’ training changes; and ‘end session’ baseline changes were deducted from ‘end session’ training changes. The resulting performance scores were designated Ta, Tb and Tc respectively. Treatment A was compared with baseline 1; treatment B with baseline 2. This ‘ipsitised’ method controls for spontaneous temperature changes; only changes over and above those occurring during comparable baseline conditions are considered to constitute a valid increase.
3. Results 3.1. Biofeedback
vs. guided imagery
The Tc scores (as the ‘end session’ scores, being the most crucial measure of the acquisition of control) are displayed graphically in fig. 1, for both groups. The results were analysed by the Mann-Whitney U test; the differences between the groups are significant (U= 0, p =
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10
FEEDBACK
0
Tc “C
IMAGERY
s 10
g:
-5 -
-10 -
-15 1
2
3
k
;
SESSIONS
Fig. 1. Mean changes imagery groups.
in finger
temperature
(Tc X 10) over sessions for the biofeedback
and the
It will be noted that, after ipsitisation, the biofeedback group produced a mean increase in all sessions except the first; whereas the imagery group produced a mean decrease in all sessions. However, the magnitude of the changes was quite small, the overall mean Tc increase for the biofeedback group being only +0.22”C; and the mean decrease for the imagery group was -0.6O”C. The differences between the groups in the early part of the sessions (Ta scores) were not significant (U= 5, n.s.); the mid-session differences (Tb scores) were just significant (U = 2, p =
4. Discussion Self-regulation of finger temperature by biofeedback was rapidly established, and the biofeedback group’s performance remained higher than that of the guided imagery group throughout all sessions. The guided imagery procedure was consistently associated with temperature decrease, perhaps reflecting the downward influ-
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ence of stimulus presentation on finger temperature (Cook et al., 1979), an influence which could not be effectively counteracted by imagery, but which could by biofeedback. This finding of the weak, or negative, influence of imagery is consistent with the bulk of the evidence from other biofeedback studies, including those concerned with blood volume pulse, electrodermal activity, and muscle activity (Yates, 1980). This would suggest that in those studies which have reported a finger temperature increase as a result of autogenic and related training procedures (e.g., Surwit et al., 1978) the effect of imagery per se within the total treatment package may possibly have been minimal, or even negative. However, the precise function of imagery within complex treatment packages can only be fully clarified by studies designed to separate out the effects of component parts, singly and in combination. There remains the possibility that, although a negative effect may result from imagery alone, a positive effect may result from the interaction between imagery and other procedures within autogenic and relaxation treatments. Certainly it would be premature to draw conclusions from this study concerning the therapeutic efficacy of relaxation and autogenic training as a whole; there is much evidence attesting to their clinical utility in problems such as headache and Raynaud’s disease, at least in the short-term (King, 1980). A further implication is that subjects learning to control skin temperature may develop the skill more efficiently, if left to devise their own strategies rather than instructed to use imagery. Evidence has now accumulated indicating that a wide range of stimuli (including instructions) may produce a decrease in finger temperature, a response clearly incompatible with the goal of clinical temperature control studies (that is, temperature increase). One interesting implication of this is that small changes (or even no change) may still demonstrate the acquisition of temperature control, since under comparable experimental conditions, but without feedback, temperature would probably decrease. Despite its fundamental importance, however, this topic has received little direct attention, nor has its significance been generally recognised. An exception is the study of Surwit, Shapiro and Feld (1976). They suggested that this decrement in temperature, and the common finding that temperature decrease is easier to achieve than increase, may be accounted for by reference to the concept of the Orienting Reflex (OR). The OR refers to widespread psychophysiological reactions, which occur in response to the presentation of stimuli, of which an important component is hand vasoconstriction. It has been most completely described by Sokolov (1963). However, it should be noted that the OR occurs in response to discrete, novel stimuli, and the relevance of the concept of OR to the kinds of. stimuli and instructions presented in biofeedback and imagery studies is therefore in doubt. Although recent extensions of OR theory (e.g. Siddle, O’Gorman and Wood, 1979) wherein such stimulus factors as ‘significance’ may partly determine the strength of the OR, suggest a possible role for the OR in accounting for temperature decrease, this is in need of further clarification. King and Montgomery (1980a) reported that, only when ‘physical manoeuvres’ were permitted, were subjects able to demonstrate temperature increase. It is pas-
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sible, therefore, that some of the increases found in the present study could have resulted from such an artifact. This is unlikely, however, for two main reasons: first, such manoeuvres as hand movements or tensing arm muscles produce a marked rapid fluctuation on the pen recording, and inspection of the recordings indicated that such fluctuations were rare and not systematically related to temperature change in any of the subjects; second, reliable differences were found between the two groups, and it would be difficult to explain why biofeedback subjects should be more prone to use manoeuvres than imagery subjects. The standard deviations reported in table 1 reveal a high degree of variability within both groups. One subject in the biofeedback group was consistently unable to demonstrate finger temperature increase, and there was marked variation from session to session and within each session for all subjects. Thus, although the changes in finger temperature were sufficient to produce significant differences between the groups, individual subjects were unable to demonstrate temperature self-regulation reliably. It is also of interest to note that the skill of temperature self-regulation was acquired within five 15 min sessions, consistent with the claim of Taub and Emurian (1976). The low level of temperature change obtained with biofeedback in this study is consistent with a number of recent reports (e.g., Surwit et al., 1976) and has been recently documented by King and Montgomery (1980b). In the present study the experimental conditions were not conducive to producing large temperature change because, as already suggested, the stimuli presented may have produced a tendency towards temperature decrease, against which the influence of biofeedback would have to compete. Also, three male subjects in the biofeedback group had a basal skin temperature of approximately 35°C which is close to a physiological ceiling. Felder, Russ, Montgomery and Horwitz (1954) have shown that once skin temperature reaches 34°C further small increases in skin temperature require considerable increases in blood flow. Thus subjects with high basal skin temperatures will be less able to produce large-scale increases. Surwit et al. (1976) examined the influence of basal finger temperature on acquisition of control by setting room temperature at 225°C for some subjects or 19.5”C for others and reported that the lower temperature was not associated with improved performance, which might have been expected if a ‘ceiling’ effect was an important determinant of the acquisition of control. However, ambient temperature is only one of several factors which determine skin temperature (Dubois, 1941). The results of Surwit et al. (1976) may, therefore, not be generally applicable to situations where elevated basal skin temperature is due to other factors. In the present study, it should be emphasised that ambient temperature was kept constant, yet high basal temperatures were still obtained for these three subjects (35°C). High basal finger temperature may still, therefore, account in part for the small magnitude of the temperature changes obtained in this study. The superiority of the biofeedback group may have been more clear-cut if subjects had been allocated to the treatment groups partly on the basis of initial stabil-
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ity point; this should be taken into account in future studies. In this study, little support was found for the alleged role of cognitive and interpersonal processes in temperature self-regulation. Ratings of task credibility, confidence in task, friendliness of experimenter and so on, were not significantly different between the groups, yet systematic differences in performance emerged. It cannot of course be argued from this that these variables play no role in self-regulatory tasks; rather that such variables are not in themselves sufficient to account for the temperature changes. The precise role of cognitive and interpersonal processes can best be elucidated by systematically varying these factors within the same treatment process. A word of caution should be sounded concerning the ‘ipsitisation’ method of scoring temperature changes used in this study. It will be remembered that ‘spontaneous’ changes during baseline were deducted from changes obtained during training; therefore if temperature decreased during baseline, the apparent magnitude of the temperature increase during training would be inflated. Although this cannot account for the systematic differences reported in this study, since temperatures in baselines 1 and 2 tended to change in both directions, care must be taken in the interpretation of results from studies using this scoring method. Finally, it is recommended that future research studies in this area should pay due attention to the potential contamination effect of stimulus presentation on finger temperature, by instituting control procedures similar to those in the present study. The main conclusions of the study are that guided imagery as utilised in this experiment does not appear to be an effective procedure for producing finger temperature increases; increases were, however, obtained by a biofeedback group, although they were of low magnitude and somewhat variable. Also some tentative evidence has suggested that cognitive and interpersonal processes cannot in themselves be regarded as sufficient explanations for changes occurring with finger temperature biofeedback.
References Blizard, D., Cowings, P. and Miller, N.E. (1975). Visceral responses to opposite types ofautogenie-training imagery. Biological Psychology, 3,49-55. Brener, J. (1974). A general model of voluntary control applied to the phenomena of learned cardiovascular control. In: Obrist, P.A. Black, A.H. Brener, J. and DiCara, L.V. (Eds.). Cardiovascular Psychophysiology: Current Issues in Response Mechanisms, Biofeedback and Methodology. Aldine: Chicago. Cook, M.R. (1974). Psychophysiology of peripheral vascular changes. In: Obrist, P.A., Black, A.H., Brener, J. and DiCara, L.V. (Eds.). Cardiovascular Psychophysiology: Current Issues in Response Mechanisms, Biofeedback and Methodology. Aldine: Chicago. Cook, M.R., Gerkovich, M.M., Graham, C., Cohen, M.D. and Anderson, F.I. (1979). Effects of cognitive and physical stimuli on finger temperature. Psychophysiology, 16, 176-177 (abstract).
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Dubois, E.F. (1941). The temperature of the human body in health and disease. In: American Institute of Physics (Ed.). Temperature: Its Measurement and Control in Science and Industry. Reinholt: New York. Dugan, M. and Sheridan, C. (1976). Effects of instructed imagery on temperature of hands. Perceptual and hlotor Skills, 42, 14. Felder, D., Russ, E., Montgomery, H. and Horwitz, 0. (1954). Relationship in the toe of skin surface temperature to mean blood flow measured with a plethysmogram. Clinical Science, 13, 251-257. Herzfeld, G.M. and Taub, E. (1976). Suggestion as an aid to self-regulation of hand temperature. Paper presented at a meeting of the Biofeedback Research Society, Colorado Springs. Hume, W.I. (1977). Biofeedback, Vol. 2. Churchill Livingston: Edinburgh. Keefe, F.J. (1978). Biofeedback vs. instructional control of skin temperature. Journal of Behavioral Medicine, 1, 3833390. Keefe, F.J. and Gardner, ET. (1979). Learned control of skin temperature: Effects of short and long-term biofeedback training. Behavior Therapy, 10, 2022210. King, N.J. (1980). The therapeutic utility of abbreviated progressive relaxation: A critical review with implications for practice. In: Hersen, M., Eisler, R. and Miller, P.M. (Eds). Progress in Behavior Modification, Vol. 10, Academic Press: New York. King, N.J. and Montgomery, R.B. (1980a). A component analysis of biofeedback induced selfcontrol of peripheral (linger) temperature. Biological Psychology 10, 1399152. King, N.J. and Montgomery, R.B. (1980b). Biofeedback-induced control of human peripheral temperature: A critical review of the literature. Psychological Bulletin, 88, 738-752. Maslach, C., Marshall, G. and Zimbardo, P.G. (1972). Hypnotic control of peripheral skin temperature: A case report. Psychophysiology, 9,600-605. Plutchik, R. (1956). The psychophysiology of skin temperature: A critical review. Journal of General Psychology, 55, 249-268. Rotter, J.B. (1966). Generalized expectancies for internal versus external control of reinforcement. Psychological Monographs, 80 (1 Whole no. 609). Schultz, J.H. and Luthe, W. (1969). Autogenic Therapy. Grune and Stratton: New York. Schwartz, G.E. (1975). Biofeedback, self-regulation, and the patterning of physiological processes. American Scientist, 63, 3 144324. Siddle, D.A., O’Gorman, J.G. and Wood, L. (1979). Effects of electrodermal lability and stimulus significance on electrodermal response amplitude to stimulus change. Psychophysiology, 16,520-521. Sokolov, E.N. (1963). Perception and the Conditioned Reflex. Macmillan: New York. Surwit, R.S., Pilon, R. and Fenton, C. (1978). Behavioral treatment of Raynaud’s Disease. Journal of Behavioral Medicine, 1, 323-336. Surwit, R.S., Shapiro, D. and Feld, J.L. (1976). Digital temperature autoregulation and associated cardio-vascular changes. Psychophysiology, 13, 242-248. Taub, E. and Emurian, C.S. (1976). Feedback aided self-regulation of skin temperature with a single feedback locus. 1. Acquisition and reversal training. Biofeedback and Self-Regulation, 1,147-168. Yates, A.J. (1980). Biofeedback and the Modification of Behavior. Plenum: New York.