The Wechsler memory scale made its first manifestation in 1945 and was one of the first standardized memory batteries. Wechsler’s original test battery was developed with the intention of providing a rapid, simple and practical memory examination (Mitrushina, 2005). The Wechsler memory scale is individually administered, composite batteries designed to enable the user to better understand various components of the patient’s memory. Groth-Marnat (2009) says that another major feature is that it provides a full range of memory functioning and has been carefully designed according to current theories of memory.
Wechsler memory scale is typically considered to be a core component of any thorough cognitive assessment which is reflected in its being ranked as the ninth most frequently used test by clinical psychologists (Groth-Marnat, 2009). According to Dehn (2011), Wechsler memory scale is a comprehensive, in-depth memory assessment battery designed for adults and older adolescents. With Wechsler memory scale an examiner can assess both the visuospatial and verbal aspects of three core memory systems which include immediate, working and long-term systems.
The Wechsler memory scale measures learning as much as the memory; for example, many of the immediate auditory memory subsets measure the ability to learn new material (Dehn, 2011). This type of scale includes tests of orientation for time and place, story recall, digit span, recall of visual designs and verbal paired associate learning. The original Wechsler memory scale reflected the earlier nonspecific conceptualizations of memory. Groth-Marnat (2009) noted that “Wechsler memory scale was composed of brief procedures on memory for number sequences, recalling a story, simple visual designs and paired words” (p. 184). Despite the fact that the early Wechsler memory scale could be logically divided into visuospatial versus auditory tasks, the overall scoring was a composite memory quotient that, similar to the Wechsler intelligence scale quotients (IQs), had a mean of 100 and a standard deviation of 15.
Advantages Of Wechsler Memory Scale Test
The advantage of using Wechsler memory scale is its brevity of administration and the large amount of data which have been collected on performance relating to a variety of neurological conditions (Kapur, 1994). Zeman, Kapur & Jones-Gotman (2012) noted that the advantage for using the Wechsler memory scale is that it is an easily obtainable and commercially available battery. The wide use of Wechsler memory scale permits comparisons of findings among centers. Also its standardization sample provides norms over the whole life span, allowing a straightforward interpretation of data (Zeman, Kapur & Jones-Gotman, 2012).
Wechsler memory scale offers a range of primary test scores, index scores and discrepancy indices, providing data for pattern and profile analyses, which is something that neuropsychologists strive for. Zeman, Kapur & Jones-Gotman (2012) indicated that “another advantage is that its revisions brought numerous extensions and improvements and its inclusion of various types of memory tests provides a relatively comprehensive approach to assessment of memory” (p. 179).
The Wechsler memory scale revised has clear advantages because it has far better normative base, is validated on diverse populations, has quite extensive studies performed on it and divided memory into various indexes, thereby allowing the possibility for measuring various aspects of memory. Wechsler memory scale (WMS-III) taps a variety of working memory functions and allows meaningful comparisons between long-term memory and short-term and working memory, as well as providing valuable information about the examinee’s ability to utilize working memory resources during learning (Dehn, 2011). The Wechsler memory scale offers the availability of critical values for discrepancies when administrated in conjunction with the WAIS-III. Dehn (2011) noted that Wechsler memory scale offers the ability to compare visual versus auditory memory across different retention intervals and the opportunity to compare long-term encoding and storage with retrieval.
Disadvantages Of Wechsler Memory Scale Tests
One of the major disadvantages of Wechsler memory scale tests is that they are psychometrically naïve, and not one of them is strongly polarized into the verbal or nonverbal domain (Zeman, Kapur & Jones-Gotman, 2012). On the other hand, Kapur (1994), noted that another main limitation of Wechsler memory scale is the inclusion of non-memory items such as reciting the alphabet, an over-emphasis on verbal memory, so that it is relatively insensitive to some forms of right hemisphere pathology. The Wechsler memory scale is limited because it includes unsophisticated methods of scoring the various procedures.
Moreover, Dehn (2011) mentioned that some disadvantages of using Wechsler memory scale is that is has a limited opportunity to assess how the examinee encodes, stores and retrieves semantic information which is the test emphasizes episodic learning and memory. It also lacks a global memory score that can be used for intra-individual analysis (Dehn, 2011). Despite the relative success of the WMS-III, there still were a number of disadvantages. These disadvantages were the equivocal factor structure, long testing time for older adults, subset overlap with the WAIS-III and problems with some of the subtests such as faces, family pictures and verbal paired associates.
When Wechsler Memory Scale Objective Test Is Administered
TheWechsler memory scale is administered to evaluate rapidly, simply and practically rather disparate group of memory functions. The objective of the test battery is to create a measure that correlates well with intelligence tests without duplicating them. Wechsler’s original test battery was developed with the intention of providing a rapid simple and practical memory examination. Mitrushina (2005) says that the original Wechsler memory scale required about 30 minutes to administer and consisted of seven subsets. The first subset is personal and current information which included six relatively simple general and personal information questions. Mitrushina (2005) says that, secondly, it requires orientation, which asked five questions relating to place and time.
Thirdly, it requires mental control, which requires the patient to count backward from 20, recite the alphabet and count by 3s with bonus points awarded for fast, perfect performance (Mitrushina, 2005). Fourthly, logical memory is used to test only immediate auditory memory for two separate orally presented stories. Wechsler memory scale requires digits forward and digits backward, which assess attention span and immediate auditory memory. Mitrushina (2005) says that visual reproduction, which tests immediate visual memory for geometric designs after a 10 second exposure. Finally, Wechsler memory scale requires associate learning, which tests recall for an orally presented list of five semantically related easy and five unrelated hard word pairs over three trials.
Frank-Stromborg (2004) noted that performance on the subtests is summed and statistically age corrected to provide a memory quotient (MQ), which in some ways is analogous to full scale IQ (mean 100, SD 15). He further says that the scoring is most useful for three factors: memory, attention and concentration. Frank-Stromborg (2004) noted that “scoring instructions published by Wechsler and Klonoff and Kennedy show norms for people in their eighties and nineties” (p. 105).
Consequently, Hasselmo (2011) noted that the Wechsler memory scale has been used in a variety of neuropsychological testing situations, including the initial studies of patient HM. This task contains a battery of different memory tasks focused on different memory systems, but some require episodic memory function more strongly than others. Hasselmo (2011) indicated that “the Wechsler memory scale includes a test of story recall, in which a paragraph is read to participants and they are scored on how well they retrieve components of this story” (p. 13). This requires elements of semantic memory and working memory but clearly also tests an episodic memory.
The Wechsler memory scale has relatively small numbers of items in each component of the task. This allows it to give a broad qualitative measure of memory function but does not give much quantitative detail. For example, the test includes a list of 20 word pairs for testing paired associate learning, whereas focused paired associate learning tasks might use 64 or more word pairs. Hasselmo (2011) there indicated that the Wechsler memory scale can distinguish between a college undergraduate and patient HM but might not distinguish between two amnesiacs with slightly differing memory capacities.
Ardila, Rosselli & Puente (1994) say that the original test has two parallel forms (Form I and Form II), but Form I is more commonly used and has been studied more. Ardila, Rosselli & Puente (1994) further explained that the two forms have sufficient parallel form reliability to be clinically interchangeable. Since Wechsler memory scale was designed to obtain a memory quotient (MQ) similar to the intelligence quotient (IQ), a MQ 12 points below the IQ have been suggested as an indication of memory impairment.
Factor analysis has disclosed the existence of three different factors loading the Wechsler memory scale: that is the short-term verbal learning, attention/concentration and orientation. In addition, Ardila, Rosselli & Puente (1994) indicated that the subsets are administered in the traditional way, but the delayed recall is introduced after about half an hour. Normative data for the Wechsler memory scale which have been developed for normal subjects, brain-damaged patients, elderly populations and children showed that the Wechsler memory scale subtests most sensitive to the effects of age are visuospatial memory tasks, remembering stories and learning pairs of associated words.
Statistical Information Relevant To Understanding The Wechsler Memory Scale Test
The major aspects of statistical information that are relevant to understanding the Wechsler memory scale include reliability and validity. Groth-Marnat (2009) says that Wechsler memory scale is good for excellent reliability. Since the index scores have a large number of items/subtests, it would be expected that their test-retest reliabilities would be higher than for the individual subtests. Studies indicate that index of the test-retest reliabilities can range from a high of about .83 for auditory memory and visual working memory to a low of .81 for visual memory and immediate memory (Groth-Marnat, 2009).
There is an extensive and quite supportive evidence for the validity of the Wechsler memory scale. Groth-Marnat (2009) studied that validity can be organized according to consent validity, correlations among the Wechsler memory scale fourth edition subtests/indexes themselves, factor analyses, correlations with other measures and relationships with special groups. Groth-Marnat (2009) researched that “content validity was based on the combination of research on previous versions of the Wechsler memory scale, expert review, client feedback, and research on cognitive process clients underwent when responding to the test items” (p. 189).
Previous statistical analysis of the earlier editions of the Wechsler Memory scale resulted in inconsistent findings, which created considerable debate regarding the true structure of the instruments and called into question the accuracy of some WMS-R/WMS-III index groupings. Groth-Marnat (2009) mentioned that the Wechsler memory scale, fourth edition, are close adhered to a factor that analytically supported three-factor model comprised of the auditory memory, visual memory and working memory.
The initial Wechsler memory scale conceptualized the human memory as a unitary construct. Hersen (2004) says that a memory quotient or MQ score was obtained by collapsing across scores of verbal and visual memory, even including scores on measures of orientation. The areas of weakness within the Wechsler memory scale include a limited standardization sample and a few reliability statistics. Hersen (2004) noted that major advances of the WMS-III include a large standardization sample, improved face validity, particularly evident in the visual memory subtests and an expansion of the subsets measuring visual memory functions.
Composite scores such as the memory quotient (MQ) of the Wechsler memory scale have shown better reliability coefficients compared to those of single subtests in the battery. Zeman, Kapur & Jones-Gotman (2012) noted that poor statistical reliability coefficients, <o.60 for single variables, were shown in the earlier versions, one of which, the WMS-I, is referred to in several studies. In the Wechsler memory scale, third edition (WMS-III), all coefficients were reported to represent substantial improvement in reliability compared to the reliability in the earlier versions. Lezak (2004) indicated that for the most part, summary score reliability coefficients are good. Excluding auditory recognition delay (.74), reliability coefficients range from .82 to .93. Individual test reliabilities are somewhat lower, with the lowest reliabilities associated with faces I and II both .74. The only test with very high reliability is Verbal Paired Associates I (.93).
In conclusion, it is important to note that statistical refinements of most new tests provide reasonable comparability across test scores, whether they are expressed in standard deviation or percentile units or as raw scores accompanied by their statistical descriptions. Lezak (2004) also indicated that the higher General Memory Index score is common in the standardization sample for subjects with lower general mental ability scores, while subjects with higher mental ability levels are likely to have lower relative memory indices. This implies that the relative independence of functions, measured by Wechsler memory scale, and memory abilities, an independence related at least in part to the differences in how many of the cognitive functions measured by Wechsler memory scales are normally distributed differently than most memory abilities.