The classification of learning difficulties in mathematics is by no means clear-cut as there are many different views on the nature of mathematical difficulties. Because of the lack of consensus and the disparate categories used, any classification of learning difficulties in mathematics is in the nature of a working hypothesis, though one based on the relevant research literature. One of the problems encountered in attempting to classify learning difficulties in mathematics is that many computations require for their solution the operation of a number of different skills or abilities. Spatial difficulties in mathematics are linked to a deficit in Thurstone's spatial factor S. They are seen in the calculations performed by Ralph, an 11-year-old boy studied by Farnham-Diggory. Most of the research has been in the area of learning through understanding versus learning by rote and, whilst good of its kind, this research is limited as far as the remediation of learning difficulties in mathematics are concerned.