Are we seeing the whole picture? Visual perception and Specific Learning Difficulties

Terminology

Marianne Frostig, an Austrian pioneer in the field of learning difficulties, observed that ’The concept of perception, like other psychological concepts, is fuzzy at the boundaries. It melts into the concept of sensation on the one hand, and of concept formation or cognition, on the other.’ (Frostig, 1961). This helps explain why there is not one clear definition of visual perception or universally agreed classification of its components. In particular, there is often inconsistency with the way that the terms ‘visual perception’ and ‘visual processing’ are used. Sometimes ‘visual perception’ is used to refer only to the initial stages of interpreting sensory information such as recognising objects, with ‘visual processing’ including more sophisticated higher-level processing, such as the mental manipulation of that visual information to solve problems. Often however, the two terms are used interchangeably. 

Within the Cattell-Horn-Carroll (CHC) model of intelligence, which forms the basis of many psychological test batteries e.g. The Intelligence and Development Scales – 2^nd Edition (IDS-2), Visual Processing (Gv) is one of the ‘broad’ abilities that ‘that can govern or influence a great variety of behaviours in a given domain’. Within this, more specific terms are used to refer to the ‘narrow’ abilities or more specialised skills that are subsumed within this factor. Interestingly, within Carroll’s original work, the term used for essentially the same factor was Broad Visual Perception. The term Visual Processing was adopted once the work of Cattell, Horn and Carroll was integrated but the narrow processes linked to remained much the same. One element that did change relates to perceptual processing speed, which is the speed at which visual stimuli can be compared for similarity or difference. This was included within Carroll’s Broad Visual Perception factor, but within the integrated CHC model it instead became one of a number of tests of the factor Processing Speed, which was defined as ‘the ability to perform simple, repetitive cognitive tasks quickly and fluently’ (Sneider & McGrew, 2012) 

As with other areas of perception, visual perception involves both ‘bottom up’ and ‘top down’ processes. The ‘bottom up’ process starts with sensation, with visual images being formed through physiological means (involving the eye, optic nerve and visual cortex). This triggers the process of interpretation for meaning, as mental construction of the information begins. Visual information is processed through two main pathways: the ventral stream or the ‘what’ pathway (involved in identifying what an object is) takes information from the visual cortex to the temporal lobe. The dorsal stream or ‘where and how’ pathway (which provides information about where something is and how to interact with it) takes information to the parietal cortex. The ‘top down’ process of visual perception interacts with the ‘bottom up’ process, and involves the application of previous knowledge, experience and memory so that what is seen can be fully interpreted and understood.

Visual perception and learning

To understand how visual perception can affect learning, it is necessary to consider its individual components. Various systems of classification have been developed in an attempt to delineate these, some broader than others in their scope. The occupational therapist Carla Schneck (1996) defined visual perception as ‘The total process responsible for the reception and cognition of visual stimuli’. This included both detecting and registering visual information through the eyes (visual-receptive component) and the cognitive processing used to interpret and makes sense of that information (visual-cognitive component). Another occupational therapist, Sidney Chu (1999a, 1999b) extended this model to present a framework that included visual-attention and visual-motor components. Although many definitions of visual perception focus only on the visual-cognitive component, since all four areas of function will need to be considered when assessing and working with people with specific learning difficulties, his broad framework has been adopted here. Chu had a particular interest in the impact of visual perceptual function and dysfunction on handwriting, but the skills outlined within his model have clear relevance for wider aspects of literacy and mathematics too. 

1. Visual-receptive component

These are the physical functions of the visual system that are involved in receiving information from the environment and creating an image. Before embarking on any assessment for specific learning difficulties, physical visual difficulties should be excluded, to ensure they are not contributing to low performance on tests, with errors being mistakenly attributed to other factors. Investigation of such difficulties would usually be in the domain of an optometrist and might include difficulties with visual acuity (clarity and sharpness of vision), accommodation (changing focus between near and far), convergence (moving both eyes inwards to focus on an object), binocular vision (using eyes together in a coordinated way), or saccadic eye movements (making the quick, precise jumps of the eyes between stationary objects). Physical visual difficulties might manifest themselves in symptoms such as blurred vision, headaches, skipping letters or lines or visual discomfort. The Specific Learning Difficulties Assessment Standards Committee (SASC) has produced guidance and a questionnaires for assessors to use to screen for visual difficulties before assessment (www.sasc.org.uk). New SASC guidance is also underway.

2. Visual-attention component

This is the ability to focus visually on some part of the environment. It consists of sustained attention (maintained focus on specific stimuli long enough to process it), selective attention (focus on a particular, relevant stimulus and the exclusion of irrelevant ones), attentional flexibility (shift of focus from one set of visual information to another) and mental tracking (attention to more than one piece of information at a time). Visual attention ensures that relevant visual details are processed e.g. when reading or writing or tackling maths problems, avoiding errors due to missed information.

3. Visual-cognitive component

This core component of visual perception can be broken down into many different skills that have been classified in a variety of ways. Chu lists five principal areas that are particularly relevant in an educational context, together with further subskills that can be identified within each of them. 

3.1 Visual discrimination. This is needed to differentiate between different visual stimuli. It includes:

• Form perception (the ability to recognise, match and name objects, shapes, patterns or symbols by essential details). This is important for distinguishing between different letters, numbers and mathematical symbols, and for learning how to form them.
• Visual closure (the ability to recognise the whole from the parts). This allows someone to complete an incomplete image – to integrate parts of an object into a whole. It can be useful for closing letters when forming them or when reading letters that have been incompletely formed by someone else, understanding that parts of a letter join to make a whole, and finishing a puzzle or geometric shape.
• Visual figure-ground perception (the ability to select and attend to relevant visual stimuli while screening out irrelevant stimuli). This is needed to be able to focus on one stimulus while screening out others that surround it. This is important for a wider range of activities: copying from the board, finding the right place on a page, identifying key words in a question or relevant numbers or symbols within a maths problem, scanning text for information, focusing on one line of text, or the relevant information on a graph in maths, or find something in a drawer or on the desk etc. 
• Perceptual constancy (the ability to recognise forms or shapes however they are presented). This is needed in literacy and maths to recognise the dominant features of something, even when there are changes in features such as shape, colour, size, position or texture. For instance, recognising letters in a different font or shapes that have been reversed or rotated.

3.2 Visual memory. This is the ability to retain a visual image of items, either briefly in short-term memory, or in long-term memory. It includes visual sequential memory – the ability to recall items in a specific order. It is important for learning letters and numbers, remembering sequences of letters for spelling, copying from the board, remembering the order of symbols and numbers in mathematical formulae and so on.

3.3 Visual spatial perception. This is the awareness of the distance of objects from oneself or another reference point (position in space) or the position and orientation of objects in relation to each other in 2 or 3 dimensional space (spatial relationship). It is needed for such skills as: judging distances and height, understanding directional words and following instructions that use them, setting out work (placing letters and words correctly in relation to the margin or baseline), achieving consistency of spacing between and within words, or distinguishing between similar forms that need to be distinguished by their spatial positioning e.g. b/d.  In maths, it may be needed in such areas as place value (realising the significance of the position of a digit in a number), understanding the relationships between lines, angles and shapes in geometry and for interpreting graphs.

3.4 Visual imagery (visualisation). This is used to generate a visual image of something that is not physically present. It can be valuable for picturing spellings, visualising the form of letters, reading comprehension, generating ideas for writing, solving problems, retaining information and planning.

3.5 Visual thinking skills. This is a dynamic aspect of visual perception that involves the ability to mentally rotate visual images, and process visual information both sequentially, and simultaneously.

The term ‘spatial ability’ is often used to refer to these last three areas of perception – visual spatial perception, visualisation and visual thinking. These skills not only require the perception of individual objects or forms, but the processing of information about their location in space and in relation to other items, and the ability to visualise and manipulate objects in space. Spatial ability is ‘a foundation for the development of quantitative reasoning’ (Reilly, 2017). 

4. Visual motor component

This is not a pure visual perceptual skill, but connects perception to action. It includes visual-motor co-ordination (needed for visually directed hand movements, as is required for skills such as pen control) and visual-motor integration (needed when information perceived visually is transferred into motor output e.g. when copying from the board). 

References

Chu, S (1999a) Course Handbook – Assessment and Treatment of Children with Developmental Perceptual Dysfunction (8^th Edition), London, Hounslow

Chu, S (1999a) Course Handbook – Assessment and Treatment of Children with Handwriting Difficulties (11^th Edition), London, Hounslow

Frostig, M., 1961. The Marianne Frostig developmental test of visual perception. Chicago: Follett Educational Corporation

Hoffman, M., Gneezy, U. & List, J.A., 2011. Nurture affects gender differences in spatial abilities. Proceedings of the National Academy of Sciences, 108(36), pp.14786–14788. Available at: https://www.pnas.org/doi/10.1073/pnas.1015182108.Astrophysics Data System+2ResearchGate+2PNAS+2

McDowell N, St Clair Tracy H, Blaikie A, Ravenscroft J, Dutton GN. Hiding in plain sight: children with visual perceptual difficulties in schools. Front Hum Neurosci. 2024;18:1496730. Published 2024 Nov 27. doi:10.3389/fnhum.2024.1496730

Reilly, D., Neumann, D. L., & Andrews, G. (2017). Gender differences in spatial ability: Implications for STEM education and approaches to reducing the gender gap for parents and educators. In M. S. Khine (Ed.), Visual-Spatial Ability: Transforming Research into Practice (pp. 195-224). Switzerland: Springer International. doi: 10.1007/978-3-319-44385-0_10

Schneck, C.M., 1996. Visual perception. In: J. Case-Smith and A.S. Allen, eds. Occupational therapy for children. 4th ed. St. Louis, MO: Mosby, pp. 373–403

Schneider, W. J., & McGrew, K. (2012). The Cattell-Horn-Carroll model of intelligence. In, D. Flanagan & P. Harrison (Eds.), Contemporary Intellectual Assessment: Theories, Tests, and Issues (3rd ed.) (p. 99-144). New York: Guilford.