Dyslexia, or a reading disability, occurs when an individual has great difficulty at the level of word reading and decoding. Comprehension of text, writing, and spelling are also affected. The diagnosis of dyslexia involves the use of reading tests, but the continuum of reading performance means that any cutoff point is arbitrary. The IQ score does not play a role in the diagnosis of dyslexia. Dyslexia is a language-based learning disability. The cognitive difficulties of dyslexics include problems with recognizing and manipulating the basic sounds in a language, language memory, and learning the sounds of letters. Dyslexia is a neurological condition with a genetic basis. There are abnormalities in the brains of dyslexic individuals. There are also differences in the electrophysiological and structural characteristics of the brains of dyslexics. Hope for dyslexia involves early detection and intervention and evidence-based instruction.
Jeffrey J. Lockman, Nicholas E. Fears, and Emily A. Lewis
Spatial ability is manifest across different psychological domains, including perception, action, and cognition. The development of spatial understanding originates in the perception-action skills of infants. When infants act on the world, either during object manipulation or locomotion, one may begin to glean the foundations of older children’s and adults’ efforts to think, reason, and solve problems more symbolically and abstractly. Even during infancy, different actions, such as reaching and locomotion, may incur different spatial demands, requiring infants to use spatial information flexibly. In the preschool years and beyond, as symbolic skills become more developed, children’s spatial abilities become more abstract, which are reflected in their abilities to think about the layout of environments and to use maps to learn about environments. Besides differences in spatial ability as a function of developmental level, individual differences in spatial ability have also been documented as a function of gender, daily experience, and blindness. Collectively, research on individual differences in spatial development suggests that training procedures can reduce differences in spatial skill that may arise in different individuals. Finally, to understand spatial development more fully, research is needed on the neural bases of spatial development, cross-cultural differences in spatial development, and the impact of technology on spatial behavior.