VALIDATION OF CONSTRUCTS I : Some relevant theory.

Version 12 02 2002 16:20 CET Copyright J. P. Krol 2001 ©. Modified 05 06 2002.

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EXPERIMENTS WITH THE MIND : MENTAL LOAD

The essays in the section validation of constructs describe experiments the author has conducted in various hostile environments and flight simulators. The hostile environments include AIRBORNE (air pilots)- FALLING (parachute jumpers) -GROUND LEVEL (fireman)- and UNDER SEA (e.g. habitat) environments.

Some methodological considerations

Like all basic science psychology is concerned with establishing functional relations among important variables.

But in psychology many variables have a high degree of abstraction.

To the extend that a variable is abstract rather then concrete we speak of it as being a construct.

Examples of constructs in psychology are : the mind, mental, mental load , intelligence, anxiety, stress .

Essentially constructs represent hypothesis that a variety of observables will correlate with one another in studies of individual differences or will be similarly affected by experimental treatments.

It is important to realize that many theories in science mainly concern statements about constructs, rather then about specific observable variables.

Yet, it is only through observable variables that these statements can be verified.

The observable variables are suggested measures of the construct and it must be kept in mind that they have to be validated for that purpose.

Specifying the domain of observables which relate to the construct is a major aspect of validation.

Another important aspect is determining to what extend these observables are affected alike by similar experimental treatments.

It must also be determined if the observables "act" as though they measure the construct.

This is done by relating the observables to a variety of treatment variables in different experiments.

The assumption in these experiments is that the treatment

variables truly represent different levels of the construct.

If the observables act as though they measure the construct they must follow the treatment variables in each experiment in a predictable manner.

When a variety of observables repeatedly have comparable curves of relationship with a variety of treatment variables representing a construct it becomes meaningful to speak of them as measuring the construct.

The measures that most consistently behave as the majority of measures can be said to have the most construct validity.

  

The mind and its mental load.

In psychology the "mind" and "mental load" have the status of constructs.

It seems useful to distinguish mental load from such constructs as "stress" or workload in general, since these may also relate to purely physical load ( requiring bodily effort).

Yet, there are many situations were physical load is almost entirely absent, but the organism is clearly under some kind of burden, as may be observed from a variety of bodily reactions.

Mental load is expected to be present when a task requires information handling or when the situation entails phenomena such as social pressure, time pressure, conflict and (the perception of ) danger.

The observables assumed to be related to the mental load construct include physiological measures.

Among these, sinus arrhythmia has been claimed to be especially sensitive for load involving information handling .

Other observable variables may require some kind of task performance.

The binary choice task has been mentioned in this respect.

In the following pages a number of experiments with human minds will

be described in which proposed measures for mental load were validated.

To strengthen the assumption that the experimental treatments were in fact different in mental load, sometimes rather dangerous (e.g. potentially deadly) conditions had to be created.

This is unethical to do under laboratory conditions which resulted in doing the experiments in the field.

An additional advantage of this was that the feasibility of applying the measurement technique in complex real life situations could be assessed at the same time.

First the experiments involving physiological variables will be described.

Performance variables will be treated afterwards.

 

Validation of physiological measures.

Three physiological variables are investigated : 1. heart rate (HR), 2. sinus arrhythmia (SA) - this is heart rate irregularity- and 3. respiratory rate (RR).

Sinus arrhythmia has been proposed as a variable with special sensitivity for mental load involving information handling .

Hence one aspect of the experimental problem was to investigate if these observables differed in sensitivity with regard to differentiating power between the type of treatment.

It was hypothised that SA would be more sensitive to treatments involving information handling and HR to treatments involving tension (from danger), with information handling minimized.

It may be pointed out that physiological reactions to "stress" in general are very similar, irrespective of the type of stressor.

They follow the pattern of the general adaptation syndrome (Selye).

Some authors have demonstrated specific stressor related reactivity for certain physiological variables but the evidence is far from conclusive.

This research is also complicated by the fact that most individuals have a

personal physiological reaction pattern, which in itself may not be constant .

The importance of developing stressor related measures is however generally agreed upon.

The experiments incorporating information handling are done with air pilots (in the air, and in flight simulators).

The experiments involving emotion ( perception of possibly mortal danger) are done with parachute jumpers and divers under water in dangerous conditions. Care was taken that these situations required minimal information handling.

One experiment was done with firemen on top of 100 ft ladders also under the assumption that there would be emotion but no relevant, task related information handling.

The experiments will be described from one medium to another, going from top to bottom.

First airborne pilots, next falling parachute jumpers, then firemen on ladders, flight simulators at ground level and finally divers under dangerous conditions under sea at various depths, finally at 90 meters.

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MOST RELEVANT LINKS :
PERFORMANCE MEASURES FOR MENTAL LOAD
PERFORMANCE MEASURES AND MENTAL LOAD
OTHER RELEVANT LINKS :
INTRODUCTION TO VALIDATION OF CONSTRUCTS II
VALIDATION OF CONSTRUCTS II
THE GLOBAL MIND AND THE USE OF WORDS
SPECIALIZED ESSAYS ADVANCED LEVEL

Copyright J. P. Krol 2001 ©. Modified 05 06 2002