propositions will lead to errors of perception such as visual illusions. Given a paragraph written with difficult handwriting, it is easier to understand what the writer wants to convey if one reads the whole paragraph rather than reading the words in separate terms. The brain may be able to perceive and understand the gist of the paragraph due to the context supplied by the surrounding words. Bottom-up processing Bottom-up processing is also known as data-driven processing, because it originates with the stimulation of the sensory receptors. Psychologist James Gibson opposed the top-down model and argued that perception is direct, and not subject to hypothesis testing as Gregory proposed. He stated that sensation is perception and there is no need for extra interpretation, as there is enough information in our environment to make sense of the world in a direct way. His theory is sometimes known as the "ecological theory" because of the claim that perception can be explained solely in terms of the environment. An example of bottom up-processing involves presenting a flower at the center of a person's field. The sight of the flower and all the information about the stimulus are carried from the retina to the visual cortex in the brain. The signal travels in one direction. Seriation In psychologist Jean Piaget's theory of cognitive development, the third stage is called the Concrete Operational State. It is during this stage that the abstract principle of thinking called "seriation" is naturally developed in a child. Seriation is the ability to arrange items in a logical order along a quantitative dimension such as length, weight, age, etc. It is a general cognitive skill which is not fully mastered until after the nursery years . To seriate means to understand that objects can be ordered along a dimension, and to effectively do so, the child needs to be able to answer the question "What comes next?" Seriation skills also help to develop problem-solving skills, which are useful in recognizing and completing patterning tasks. Piaget's work on seriation Piaget studied the development of seriation along with Szeminska in an experiment where they used rods of varying lengths to test children's skills. They found that there were three distinct stages of development of the skill. In the first stage, children around the age of 4 could not arrange the first ten rods in order. They could make smaller groups of 2–4, but