Mobile

Mobile is a test of auditory-verbal sequential short-term memory, based on recall of digits. It is a well established fact that individuals with dyslexia or specific learning difficulty typically experience problems with recall of digits (Beech, 1997; Thomson, 1993; Turner, 1997), and digit span is a feature of the vast majority of assessment batteries used for diagnosis of dyslexia (Reason, 1998). Although digit span is normally a spoken test, there is good evidence that the form of the test used in LASS correlates highly with traditional forms, such as those used in the Wechsler Intelligence Tests and the British Ability Scales, and is therefore a valid measure of auditory-verbal memory.

Auditory-verbal short-term memory is critical for literacy development, especially for the acquisition of phonic skills, i.e. mapping of letters (graphemes) on to sounds (phonemes), and for the storage of phonological codes in short-term memory during word recognition and processing of text. There is also a well-established connection between reading and memory (for reviews, see Baddeley, 1986; Beech, 1997; Brady, 1986; Jorm, 1983; Wagner and Torgesen, 1987). The predominant view in the research literature is that phonological processes underpin the development of a phonological recoding strategy in reading, and that working memory plays a significant role in this strategy, enabling constituent sounds and/or phonological codes to be held in the short-term store until these can be recognised as a word and its meaning accessed in longterm memory (e.g. Gathercole and Baddeley, 1993a; Wagner et al, 1993).

Short-term auditory-verbal memory is sometimes called ‘working memory’ because it is the system which we use when we have to hold information for a brief period of time while we process it. Working memory is a limited-capacity system, and unless rehearsed or transferred to longer-term storage, information in working memory is only retained for a few seconds (Baddeley, 1986). For example, in order to understand what a person is saying to us we have to hold their words in working memory until they get to the end of a sentence (or equivalent break), then we can process those words for their meaning. We cannot process each individual word for meaning as we hear it because by themselves words do not convey sufficient meaning. Furthermore, words heard later in an utterance can substantially alter the meaning of words heard earlier (e.g. “The man opened the magazine — then he carefully extracted the remaining bullets it contained”). Other examples of working memory include trying to hold a telephone number in mind while we dial it, and carrying out mental arithmetic.

The relevance of auditory-verbal working memory to literacy skills should be obvious — in the same way that it is necessary to hold spoken words in memory in conversation, the student must hold letters and syllables in memory when decoding words. This is very important in the development of phonic skills. The majority of dyslexic students have problems in this area of cognitive processing (Thomson, 1989). Awaida and Beech (1995) found that phonological memory at age 5 predicted nonword reading (i.e. phonics skills) at 6 years. When reading continuous text for meaning the student must also hold words in memory until the end of the phrase or sentence. Poor working memory will thus affect reading comprehension. Of course, visual memory skills will be involved in much of this cognitive activity, especially for beginning readers who have not progressed to phonics, and also for more competent readers whose capacity for rapid visual recognition of words steadily increases with age. Nevertheless, auditory-verbal working memory remains a significant factor in reading development and in writing as well.

Students with weaknesses in auditory-verbal working memory also tend have difficulty in monitoring their written output, and are inclined to miss letters, syllables and/or words out when they are writing. (For reviews of research on the connections between verbal memory and reading see Baddeley, 1986; Brady, 1986; Jorm; 1983; Wagner and Torgeson, 1987.)

More recently, further research has suggested a very close connection between auditory memory span and articulation (speech) rate (Avons and Hanna, 1995; McDougall and Hulme, 1994). It could well be that articulation rate is an index of the efficiency with which phonological representations of words can be located in memory and activated (i.e. spoken). In turn, this could be closely related to how quickly cognitive representations of words being read can be located in the orthographic and semantic lexicons and activated (i.e. recognised and understood). The three lexicons (phonological, orthographic and semantic) are all believed to be closely related (Rayner and Polatsek, 1989).

When interpreting the results from Mobile, as well as determining whether scores fall below the critical thresholds (see Section 4.1.2), significant discrepancies between the scores on this module and that on the Reasoning module may also be taken into account. In this case, the procedure described in Section 4.3.3 should be employed.

Like the other auditory tasks in LASS, Mobile requires adequate hearing ability. Where a teacher suspects that a low score on Mobile could be due to poor hearing, inspection of the data pages should help to resolve the question. If the problem is mainly one of hearing, errors will usually be found to be scattered throughout the test results. If it is due to poor memory, errors will tend to increase as the test progresses and the memorisation load steadily increases.