4.6: Behavioural Methods
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Besides using methods to measure the brain’s physiology and anatomy, it is also important to have techniques for analyzing behaviour in order to get a better insight on cognition. Compared to the neuroscientific methods, which concentrate on neuronal activity of the brain regions, behavioural methods focus on overt behaviour of a test person. This can be realized by well defined behavioural methods (e.g. eye-tracking), test batteries (e.g. IQ-test) or measurements which are designed to answer specific questions concerning the behaviour of humans. Furthermore, behavioural methods are often used in combination with all kinds of neuroscientific methods mentioned above. Whenever there is an overt reaction on a stimulus (e.g. picture) these behavioural methods can be useful. Another goal of a behavioural test is to examine in what terms damage of the central nervous system influences cognitive abilities.
A Concept of a behavioural test
The tests are performed to give an answer to certain questions about human behaviour. In order to find an answer to that question, a test strategy has to be developed. First it has to be carefully considered, how to design the test in the best way, so that the measurement results provide an accurate answer to the initial question. How can the test be conducted so that founding variables are minimal and the focus really is on the problem? When an appropriate test arrangement is found, the defining of test variables is the next part. The test is now conducted and probably repeated until a sufficient amount of data is collected. The next step is the evaluation of the resulting data, with the suitable methods of statistics. If the test reveals a significant result, it might be the case that further questions arise about neuronal activity underlying the behaviour. Then neuroscientific methods are useful to investigate correlating brain activities. Methods, which proved to provide good evidence to a certain recurrent question about cognitive abilities of subjects, can bring together in a test battery.
Example: Question: Does a noisy surrounding affect the ability to solve a certain problem?
Possible test design: Expose half of the subject to a silent environment while solving the same task as the other half in a noisy environment. In this example founding variables might be different cognitive abilities of the participants. Test variables could be the time needed to solve the problem and the loudness of the noise etc. If statistical evaluation shows significance: Probable further questions: How does noise affect the brain activities on a neuronal level?
Are you interested in doing a behavioural test on your own, visit: the socialpsychology.org website. [2]
Test batteries
A neuropsychological assessment utilizes test batteries that give an overview on a person’s cognitive strengths and weaknesses by analyzing various cognitive abilities. A neuropsychological test battery is used by a neuropsychologist to assess brain dysfunctions that can rise from developmental, neurological or psychiatric issues. Such batteries can appraise various mental functions and the overall intelligence of a person.
Firstly, there are test batteries designed to assess whether a person suffers from a brain damage or not. They generally work well in discriminating those with brain damage from neurologically impaired patients, but worse when it comes to discriminating them from those with psychiatric disorders. The most popular test, Halstead-Reitan battery , assesses abilities ranging from basic sensory processing to complex reasoning. Furthermore, the Halstead-Reitan battery provides information on the cause of the damage, the brain areas that were harmed, and the stage the damage has reached. Such information is valuable in developing a rehabilitation program. Another test battery, the Luria-Nebraska battery , is twice as fast to administer as the Halstead-Reitan. Its subtests are ordered according to twelve content scales (e.g. motor functions, reading, memory etc.). These two test batteries do not focus only on the absolute level of performance, but look at the qualitative manner of performance as well. This allows for a more comprehensive understanding of the cognitive impairment.
Another type of test batteries, the so-called IQ tests, aims to measure the overall cognitive performance of an individual. The most commonly used tests for estimating intelligence are the Wechsler family intelligence tests . Age-appropriate test versions exist for small children from age 2 years and 6 months, school-aged children, and adults. For example, the Wechsler Intelligence Scale for Children, fifth edition (WISC-V) measures various cognitive abilities in children between 6 and 16 years of age. The test consists of multiple subtests that form five different main indexes of cognitive performance. These main constructs are verbal reasoning skills, inductive reasoning skills, visuo-spatial processing, processing speed and working memory. Performance is analyzed both compared to a normative sample of similarly aged peers and within the test subject, assessing personal strengths and weaknesses.
The Eye Tracking Procedure
Another important procedure for analyzing behavior and cognition is Eye-tracking. This is a procedure of measuring either where we are looking (the point of gaze) or the motion of an eye relative to the head. There are different techniques for measuring the movement of the eyes and the instrument that does the tracking is called the tracker. The first non-intrusive tracker was invented by George Buswell.
The eye tracking is a study with a long history, starting back in the 1800s. In 1879 Louis Emile Javal noticed that reading does not involve smooth sweeping of the eye along the text but rather series of short stops which are called fixations. This observation is one of the first attempts to examine the eye’s directions of interest. The book of Alfred L. Yarbus which he published in 1967 after an important eye tracking research is one of the most quoted eye tracking publications ever. The eye tracking procedure is not that complicated. Video based eye trackers are frequently used. A camera focuses on one or both eyes and records the movements while the viewer looks at some stimulus. The most modern eye trackers use contrast to locate the center of the pupil and create corneal reflections using infrared or near-infrared non-collimated light.
There are also two general types of eye tracking techniques. The first one – the Bright Pupil is an effect close to the red eye effect and it appears when the illuminator source is onset from the optical path while when the source is offset from the optical path, the pupil appears to be dark (Dark Pupil). The Bright Pupil creates great contrast between the iris and the pupil which allows tracking in light conditions from dark to very bright but it is not effective for outdoor tracking. There are also different eye tracking setup techniques. Some are head mounted, some require the head to be stable, and some automatically track the head during motion. The sampling rate of the most of them is 30 Hz. But when we have rapid eye movement, for example during reading, the tracker must run at 240, 350 or even 1000-1250 Hz in order to capture the details of the movement. Eye movements are divided to fixations and saccades. When the eye movement pauses in a certain position there is a fixation and saccade when it moves to another position. The resulting series of fixations and saccades is called a scan path. Interestingly most information from the eye is received during a fixation and not during a saccade. Fixation lasts about 200 ms during reading a text and about 350 ms during viewing of a scene and a saccade towards new goal takes about 200 ms. Scan paths are used in analyzing cognitive intent, interest and salience.
Eye tracking has a wide range of application – it is used to study a variety of cognitive processes, mostly visual perception and language processing. It is also used in human-computer interactions. It is also helpful for marketing and medical research. In recent years the eye tracking has generated a great deal of interest in the commercial sector. The commercial eye tracking studies present a target stimulus to consumers while a tracker is used to record the movement of the eye. Some of the latest applications are in the field of the automotive design. Eye tracking can analyze a driver’s level of attentiveness while driving and prevent drowsiness from causing accidents.