Visual illusions in geology
Examples of visual illusions in the laboratory are well documented, but what about illusions that occur during field observation of geological structures? In this article I discuss a study involving geologists and non-geologists and define some of the problems that may arise during geological field and laboratory work.
Stages of textural maturity in sedimentary rocks
ABSTRACT Four stages of textural maturity in sediments are defined by the occurrence of three sequential events (1) removal of clays, (2) sorting of the sand fraction, and (3) attainment of high roundness. A binomial terminology is introduced wherein the term denoting textural maturity is prefixed to the rock-composition name, obtained from the mineralogy of the silt-sand-gravel portion (e.g., "submature graywacke").
Eye-movement parameters and pattern discrimination
Pattern discrimination was studied in a visual-search task by recordingan O’s eye movements while he determined how many of eight patterns, arranged in a square around a standardpattern, matched the standard pattern. The results demonstrate the role of eye movements in visual search and human pattern discrimination. The mean duration of an eye fixation on a pattern, the probability of fixating it, the probability ofrefixating it, and the sequence in which patterns were fixated were all systematically related to various pattern measures. Multivariateanalyses showed modest correlations between the duration of individual eye fixations and various pattern measures. Relative characteristics of patterns influenced performance more than absolute characteristics of patterns. Patterns that matched a standard were fixated more often and longer than patterns that did not match a standard. The order in which patterns were fixated depended upon their relative characteristics. The results were consistent with a model ofpattern discrimination consistingoftwo stagesin which (1) features of a fixated pattern are abstracted and encoded, and (2) these features are then compared with the features ofanother pattern.