Assessment of visual-spatial working memory
Pentland, Anderson, Dye, and Wood (2003, pp. 144-145) define nonverbal memory as a “process that relates to the encoding and retrieval of spatial representations” and suggest that “nonverbal memory is more precisely defined in terms of a synthesis of visual and spatial (visuo-spatial) information”. They suggest that, whereas the visual processing system processes object properties such as shape and color, the spatial processing unit assesses properties such as location and size (Pentland et al., 2003).
Historically, assessing visual-spatial working memory has been more challenging than assessing verbal working memory, due to the relative ditficulty of designing tasks that are pure measures of visual-spatial constructs (Pickering, 2001). For example, verbal mediation is often used by respondents when performing many tasks of visual-spatial working memory (Pulos & Denzine, 2005).Two measures that are relatively free of verbal mediation, however, are the Corsi Block Test (Milner, 1971) and the Visual Patterns Test, devised by Wilson, Scott, and Power (1987), developed by Logie and Pearson (1997), and normed by Della Sala, Gray, Baddeley, Allamano, and Wilson (1999).
The Corsi Block Test (CBT) was designed in the early 1970s to be used in neuropsychology' practice, and is an extension of the Cube Imitation Test, developed by Knox (1913) to diagnose “mental retardation” in early twentieth-century immigrants to the United States (Vecchi & Richardson, 2001).The CBT typically consists of wooden pegs arranged in a nonsymmetrical pattern, which are attached to a wooden board.The examiner taps specific blocks in a predetermined sequence (usually at the rate of one block per second), and upon cue, the respondent repeats the sequence. By increasing the number of blocks tapped, the examiner controls for the difficulty of the task (Pickering, 2001). Although the Corsi Block Test has been used extensively to assess individuals suspected of neuropsychological deficits, standardization of the assessment has been lacking (Kessels, van Zandvoort, Postma, Kappelle, & de Haan, 2000). In fact, Berch, Krikorian, and Huha (1998) identified significant variations in their review of 38 empirical studies utilizing the CBT. Such variations were associated with physical characteristics such as the color of the board, number of blocks positioned on the board, block size, block placement, and display area. Also noted in their review were significant administrative differences, for example, pointing procedure, block-tapping rate, starting point, trials per level, discontinue criterion, and block-tapping sequences. By using a computerized version of the CBT,Vandierendonck, Kemps, Fastame, and Szmalec (2004) investigated the CBT s potential load on working memory and concluded that the “findings are clear and fit in well with the working memory framework of Baddeley and Hitch (1974)”.
Whereas the CBT is purported to measure visual and spatial working memory, the Visual Patterns Test (VPT) is designed to be a “purer” assessment of visual working memory (Della Sala et al., 1999). The VPT consists of crossword puzzlelike grids (without the numbers) that increase in the number of cells from four (i.e., a 2 x 2 matrix) to 30 (i.e., a 5 x 6 matrix). In each grid, the individual cells are either black or white. Each grid is displayed on a card, which is presented to the respondent for three seconds. When it is removed from view, the respondent is asked to reproduce the grid by marking the cells in an empty grid of the same size as that presented. Scoring is based on the number of correctly filled cells in the most complex pattern accurately recalled.