|Perception is a process of registering sensory stimuli as meaningful experience. The differences between sensation and perception have varied according to how the terms are defined. A common distinction is that sensations are simple sensory experiences, while percepts are complex constructions of simple elements joined through association. Another is that perception is more subject to the influence of learning. Though hearing, smell, touch, and taste perceptions have all been explored, vision has received the most attention. Structuralist researchers such as Edward Bradford Titchener focused on the constituent elements of visual perceptions, whereas Gestalt psychology has stressed the need to examine organized wholes, believing humans are disposed to identifying patterns. Visual objects tend to appear stable despite continually changing stimulus features (such as ambient light, perspective, ground vs. figure arrangement), which enables an observer to match a perceived object with the object as it is understood to exist. Perceptions may be influenced by expectations, needs, unconscious ideas, values, and conflicts.