he or she can recall correctly in the given order on half or more trials. In an early and influential article, "The Magical Number Seven, Plus or Minus Two", Miller suggested that human short-term memory has a forward memory span of approximately seven plus or minus two items and that that was well known at the time (apparently originating with Wundt). Later research reported that this "magical number seven" is roughly accurate for college students recalling lists of digits, but memory span varies widely across populations and material. For example, the ability to recall words in order depends on characteristics of those words: fewer words can be recalled when the words have longer spoken duration; this is known as the word-length effect, or when their speech sounds are similar to each other; this is called the phonological similarity effect. More words can be recalled when the words are highly familiar or occur frequently in speech. Recall performance is better when all of the words are taken from a single semantic category (such as games) than when the words are chosen randomly. A later estimate of short-term memory capacity reported that the capacity was about four pieces, or "chunks", of information. Other notable theories argue against measuring capacity in terms of the number of elements. In the visual domain, several studies report no fixed capacity limit in terms of total number of items that can be retained. Instead, some investigators have argued for a limited resource that can be flexibly shared between items held in short-term memory, with some items (in the focus of attention) being allocated more resource and being recalled with greater fidelity. Many of these experiments have used delayed response tasks that have a continuous, analogue response space, rather than using a binary (correct/incorrect) recall method as is often used in change detection tasks. Instead of asking people to report whether a change occurred between the memory and probe array, delayed reproduction tasks require participants to reproduce the precise quality of a visual feature, e.g. an object’s orientation or colour. Rehearsal Rehearsal is the process of repeating information to be retained, ostensibly keeping it in short-term memory. Each repetition reenters the information into short-term memory, thus keeping that information for another 10 to 20 seconds (the average storage time for short-term memory). Chunking Chunking is a technique that allows memory to remember more things. Chunking involves organizing material