The Discriminative Validity of Three Visual Perception Tests
Brown, T., Elliott, S., Bourne, R., Sutton, E., Wigg, S., Morgan, D., Glass, S., Lalor, A., New Zealand Journal of Occupational Therapy
Visual perception is an essential aspect of one's ability to mentally manipulate visual information in order to solve and respond to problems (Kurtz, 2006). Visual perception, therefore, facilitates one's overall performance capacity in regards to safely and independently performing self care tasks and participating in work/leisure related activities (Cooke, McKenna, Fleming, & Darnell, 2006; Erhardt & Duckman, 1997; Scheiman, 1997a). Unfortunately the complexity of the human visual system renders it "vulnerable to many dysfunctional skills which can severly impact its effectiveness as an information processing tool" (Su, Chein, Chen, & Lin, 1995, p. 3).
Consequently, occupational therapists routinely assess visual perception, particularly when working with clients who present with pre-existing clinical conditions commonly associated with visual perceptual dysfunction (American Occupational Therapy Association, 1991, 2008; Canadian Association of Occupational Therapists, 1990). Diagnoses that are often associated with visual perceptual dysfunction include: multiple sclerosis, dementia, cerebral palsy, Parkinson's disease, cerebrovascular accident, and aquired brain injury (Bouska et al., 1990; Edmans, Towle, & Lincoln, 1991; Glosser, Gallo, Duda, de Vries, Clark et al., 2002; Kozeis, Anogeianaki, Mitova, Anogianakis, Mitov, et al. 2007; Lezak, 1995; Mercier, Audet, Hebert, Rochette, & Dubois, 2001; Neistadt, 1990; Ogden, 1990; Unsworth, 1999; York & Cermak, 1995).
Three tests that are commonly used by American healthcare professionals to assess adult visual perception are the Developmental Test of Visual Perception -Adolescent and Adult (DTVP-A; Reynolds, Pearson, & Voress, 2002), the Motor-Free Visual Perceptual Test--3rd edition (MVPT-3; Colarusso & Hammill, 2003), and the Test of Visual Perceptual Skills (non-motor) 3rd edition (TVPS-3; Martin, 2006). Each of these tests was developed in the United States (US) and emerged from revisions made to pre-existing, paediatric test editions (Colarusso & Hammill, 1972, 1996, 2003; Gardner, 1982, 1992; Hammill et al., 1993; Martin, 2006; Reynolds et al., 2002).
As the DTVP-A, MVPT-3, and TVPS-3 are commonly used outside the US, it is essential to assess their psychometric properties in other cultural contexts (Bishop & Curtin, 2001; Burtner, Whilhite, Bordegaray, Moedl et al., 1997; Grieve & Gnanasekaran, 2008; Rodger, 1994). Consequently, the authors of this study deemed it important to investigate whether tests developed and standardised within one country operate in a similar manner in other countries. For example, if a test contains certain items that are meaningful and relevant within one cultural environment but not in another, then respondents answering test items might be disadvantaged by answering the test items incorrectly. In other words, the test scores of respondents from cultural environments other than the one in which the test was originally developed might not be truly reflective of their abilities and skills. Hence the aim of this study is to investigate the discriminative validity of these three visual perceptual tests.
Very few peer-reviewed studies have adopted this focus (Canivez, 2005; Hodgson, 2005; King, 2005). Therefore this study investigated the DTVP-A, MVPT-3, and TVPS-3 in an Australian context by comparing the performance of two groups, one group of individuals diagnosed with a neurological impairment and one group with no known impairment, according to these three tests. This study also investigated the ability of the DTVP-A, MVPT-3, and the TVPS-3 to successfully discriminate between two groups of participants with a known difference, those being with and without a diagnosed neurological impairment.
The literature review provides an overview of visual perception, the subtypes of visual perception that have been identified in the empirical literature, and the impact of visual perception dysfunction on the occupational performance of individuals. As well, how visual perception is typically assessed by therapists is discussed including a brief description of the three tests frequently used to assess individuals with suspected visual perceptual problems. Finally, the issue of discriminative validity, a trait of standardised tests, is covered.
Visual perception involves "a number of related abilities that tend to be interdependent upon one another" (Kurtz, 2006, p. 33). Consequently this makes it difficult to explicitly distinguish one perceptual problem from another, which is further complicated by specialists defining problems using different terminology (Kurtz). Having noted this, five theoretical constructs of visual perception consistently appear in the literature: spatial relationships, visual discrimination, figure ground, visual closure, and visual memory (Chalfant & Scheffelin, 1969; Colarusso & Hammill, 2003; Martin, 2006; Reed, 2001; Scheiman, 1997a). A sixth construct, form constancy, has also been recognised by several authors (Frostig, Lefever, & Whittlesey, 1961; Reynolds et al., 2002).
The first five above mentioned skills encompass a person's abilities to orient their body in space and perceive the relative position of objects (spatial relationships); discriminate between the features of different objects, such as position, colour and shape (visual discrimination); distinguish an object from surrounding or background objects (figure ground); identify a whole figure when only fragments of the figure are presented (visual closure); and recognise a stimulus item following a brief interval (visual memory). Finally, the form constancy visual perceptual skill constitutes the ability to recognise the dominant features of objects when they appear in different sizes, shadings, and/or textures (Reynolds et al., 2002; Unsworth, 1999)
Impact of visual perceptual dysfunction
Visual perception disorders occur as a result of dysfunction within the association areas of the brain and/or their complimentary nerve tracts (Reed, 2001; Su et al., 1995). Such disorders may be "immediately observable in any context", while others may only become apparent when a person is "functioning within certain distracting environments" (Connor & Padula, 2005, p. 95). Phipps (2006, p. 576) noted that people with visual perceptual disorders commonly experience difficulties with judging distance and position, "interpreting the meaning of objects in their environment" and "recognising, identifying, or remembering colours in their environment". Moreover, Connor and Padula (2005) recognised visual perceptual deficits to be associated with disturbances in co-ordination, posture and ADL performance. Indeed, persons with visual perceptual dysfunction have been noted to experience difficulties with dressing, eating, reading, writing, driving, housekeeping, and participating in leisure activities (Cooke et al., 2006; Edmans et al., 1991; Faye, 2005; Gianutsos, 2005; Ishihara, Ishihara, Nagamachi, Osaki, & Hiramatsu, 2004; Mercier, et al., 2001; Reed, 2001; Schneck, 2005).
Such performance deficits may also place one at risk during attempts to perform what many would consider to be simple tasks of daily living (Golisz & Toglia, 2003; Phipps, 2006). For example, a person who cannot judge the distance and spatial relationship of their foot to a step has a heightened risk of experiencing a serious fall when negotiating stairs; while another who cannot identify/ recognise the significance of various traffic signs is at an increased risk of being involved in a traffic accident when commuting/ travelling (Phipps, 2006). Golisz and Toglia (2003) also …
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Publication information: Article title: The Discriminative Validity of Three Visual Perception Tests. Contributors: Brown, T. - Author, Elliott, S. - Author, Bourne, R. - Author, Sutton, E. - Author, Wigg, S. - Author, Morgan, D. - Author, Glass, S. - Author, Lalor, A. - Author. Journal title: New Zealand Journal of Occupational Therapy. Volume: 58. Issue: 2 Publication date: September 2011. Page number: 14+. © 2008 New Zealand Association of Occupational Therapists. COPYRIGHT 2011 Gale Group.
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