Biological Psychology
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Biological Psychology Managing Editor: Malcolm Lader Co-Editor: Peter Venables Volume 15,1982 NORTH-HOLLAND PUBLISHING COMPANY AMSTERDAM Biological Psychology 15 (1982) 151-169 151 North-Holland Publishing Company COVARIATION AND CONSISTENCY OF ACTIVATION PARAMETERS Jochen FA HREN BERG and Friedrich FOF.RSTER Freiburg University, D-7800 Freiburg, F.R.G. Accepted for publication 7 June 1982 Individual differences in activation processes, as well as the consistency and predictability of these differences, constitute a classical issue eliciting much theoretical discussion in this field and as such poses an essential question for any practical application of psychophysiological methods. A typical activation experiment assessing 125 male students on four self-report and 21 physiological measures under five conditions (rest, mental arithmetic, interview, anticipation and blood taking) was performed supplying an empirical basis for a multivariate analysis. A partition of covariance, factor analyses, item analyses and scale construction procedures as well as models engaging an increasing number of components were used to study the covariation and consistency of these activation parameters. Several biometric problems that are generally thought to complicate the evaluation of such data (i.e. non-linear relations, the problem of initial values, differing sensibility curves of physiological response systems, individual response specificities) are considered and tested empirically. Findings suggest that the use of a single variable or a composite measure as an 'indicator' of individual differences in state or reaction aspects of activation is inadequate, due to empirical inconsistency and the lack of predictability between functional subsystems. A multicomponent model or a set of marker variables , having empirically derived discriminative efficiency as well as reliability estimates, seem to be preferable. 1. Introduction The covariation of activation parameters is one of the classical issues in psychophysiology and as such has been the subject matter of several studies and critical reviews (Duffy, 1972; Wenger and Cullen, 1972; Lader, 1975; Haynes and Wilson, 1979; Myrtek, 1980; Fahrenberg, 1982). Although there is a broad agreement as to the generally low common variance in psychophysio- logical measures, the consequences regarding methodology and applied psy- chophysiology seem to be less clear. While there is little support for an unidimensional continuum of activation this theoretical construct continues to * Requests for reprints should be addressed to Jochen Fahrenberg, Forschungsgruppe Psycho- physiologie, Universitat Freiburg, Schillhof 5, D-7800 Freiburg, F.R.G. 0301-05 ll/82/0000-0000/$02.75 © 1982 North-Holland 152 J. Fahrenberg and F. Foerster / Consistency of activation 153 J. Fahrenberg and F. Foerster / Consistency of activation be viable and is widely used in present day psychophysiology. Many contribu- Rest phase 1 (recording 120 sec). tors refer explicitly, or at least implicitly, to such concepts like activation or Mental arithmetic 1 (recording 120 sec). for instance arousal and many experimenters tend to suggest that, , a single Interview (four recordings of 30 sec each before subject spoke). parameter of electrodermal activity or of heart rate change is not of interest per M'ental arithmetic 2 (recording 120 sec, replication of the task using a parallel se but could be viewed as an indicator of such theoretical constructs. In form). univariate experimentation analysis of variance designs have been primarily Anticipation of blood sample taking (recording 60 sec). applied focusing on main effects, thus avoiding the basic problem of covaria- Blood taking (recording 60 sec). tion and consistency of activation parameters. Such problems are, however, Rest phase 2 (recording 120 sec). unavoidable as soon as individual differences are correlated or predicted in Self-ratings of the subject's state in Rest phase 1 were obtained at the end of practical application of psychophysiological methods, particularly when a ' 'alert' ' that phase by six Likert-type scales: , tense', perceived 'heart rate , multimodal assessment of complex treatment effects is undertaken. 'muscular tension' 'irritated' perceived , , subjective evaluation of the experiment Concerning the covariation problem, a large number of studies have been conducted, most of them itself as to whether it was 'meaningful' or not. After each preceding phase the , however, applying small-scale analyses with very subjects were asked to estimate their state change with Rest phase 1 as a limited samples of subjects and variables. Moreover in this field there has been a neglect in the use of those concepts and multivariate procedures that are reference point, using a 21 step verbally anchored graphic rating scale (0 = being familiar in differential psychology and that have proved useful in the construc- unchanged, ± 10 being the highest possible increase or decrease respectively). Polygraph recordings were obtained in 10 channels: electrocardiogram tion of psychological tests (i.e. concepts of item analysis, internal consistency, partition of covariance in a four-modal data box - subjects, variables, condi- ECG, finger plethysmogram, electrodermal activity EDA, pneumogram, elec- tions, replications of particular conditions - and factor analysis) to obtain tromyogram F.MCJ (forehead and extensor digitorum), eye movement and blink activity, electroencephalogram EEG (02-P4), finger temperature, and an communality estimates and dimensionality of complex data sets. The present multivariate study is designed: (1) to provide a sufficient intermittent noninvasive blood pressure recording. Detailed information about empirical basis as to the covariation and consistency of activation parameters; procedure, recording technique, automatic parameter abstraction by means of and (2) to assess the appropriateness of an unidimensional as compared to a specially developed computer software, and scoring has been reported elsewhere (Fahrenberg et al. 1979, 1982). multicomponent model of activation processes. Altogether six psychological (self-report) variables of the activation process being considered here and 161 physiological parameters were obtained com- 2 . Methods prising the primary item pool. This large number of parameters has been derived because: (1) some parameters have been arithmetically derived from 2.1. Procedure primary measurement, e.g. pulse wave velocity (i?-wave of the ECG and finger pulse); (2) special parameters from EEG and EDA recordings have been included for exploratory purposes; and (3) several variability measures were The empirical data are taken from a typical activation experiment consider- ing a broad spectrum of dependent variables under various stimulus condi- used. The general intention aimed at providing a broad spectrum of parame- tions. The present experiment has been designed to determine whether individ- ters, though many of these may be rather unfamiliar to most researchers in this ual differences in activation state and activation reaction can be reliably field, and subsequently applying a strict empirical selection procedure to this predicted from five dispositional variables. Since this investigation has been primary item pool, thus yielding a set of relevant variables. reported elsewhere (Fahrenberg, Walschburger, Foerster, Myrtek and Miiller, 2.2. Selection of activation parameters 1979, 1982) an abbreviated summary of the procedures may suffice. Male student volunteer subjects (jV= 125) took part in a study comprising: (1) An empirically based rational selection procedure was applied to reduce the personality assessment by paper and pencil tests; (2) cardiovascular assess- primary item pool. In order to be defined as an activation variable a particular ment; and (3) a typical activation experiment, subjects being randomly as- variable should meet the following criteria: signed to two different instruction sets. Self-report data and physioligical (1) Using a two-way ANOVA-design (subjects, conditions) both the subject recordings were obtained for each of the following conditions which were and the condition effects should be significant at the p" 0.05 level for the presented in identical order to obtain comparable results: given variable. /. Fahrenberg and F. Foerster / Consistency of activation 155 /. Fahrenberg and F. Foerster / Consistency of activation (2) At least two experimental conditions should be discriminated signifi- cantly from Rest phase 1 by that variable (Scheffe tests). (3) The short-term stability coefficient, used as a reliability estimate by comparing Mental arithmetic 1 and Mental arithmetic 2 (about 20 min later) should be r > 0.60. u (4) There should be no extreme anomalies in the distributions (i.e. skewness <3.0 and kurtosis ' 10.0 during Rest phase 1 and Mental Arithmetic 1); use oor iLnc or-o - of data transformations (e.g. McCall's transformation), basically would not oooooodo oooooooo ooooooooo solve such problems since the entire data set must be subjected to transforma- tion, and still, extreme anomalies in distribution could occur for the one or the other experimental condition. y w « (5) There should be no substantial redundancy of this variable when " f i s c x x > fl X c C/2 \ 3 3 3 compared to other parameters of the same recording channel or functional / a 11 . a. U . ' " " X E a. i " e3 rt 3 o - - system respectively, i.e. the coefficient rws < 0.70 (see below for partition of o o o o S E S S 2 d =? 9 d