An experimental investigation of memory span

Words. —The unit consisted of a five, six, or seven letter abstract noun of one or two syllables. In constructing the series for the test the units were chosen so that every series of a given unit length contained exactly the same number of letters and the same number of syllables. For example, each of the ten series of four-unit length contained eight syllables and twenty-four letters; each series of five-unit length contained nine syllables and thirty-two letters, etc. The series varied in length from four to nine units inclusive. The procedure in recall was the same as for concrete words. Memory for Commissions. —The unit in this test consisted of a simple command. An example of such a unit is the following: "Put a circle around A. " Another is: "Put a comma below 6. " Each unit was five or six words in length. The series varied in length from one to five units inclusive. As mentioned above the method of recall in this test differed from the others. Instead of repeating the commission orally the subject performed the task on a card placed before him for that purpose. As in the other teats, however, each commission was to be performed in the order of its appearance in the series. Simple Sentences. —In this test a simple declarative sentence constituted a unit. Each sentence consisted of six words in eight syllables. An example of a unit is the following: "Mary waved to the cheering crowd. " The series varied in length from one to five units inclusive. In recalling each series the subject was to repeat each unit, i.e., each sentence, verbatim and in its proper order in the series. Auditory Tests. —In addition to the ten visual tests listed above, there were also three auditory tests—tests for consonants, concrete words and abstract words. The same procedure was followed in constructing these tests as in constructing the visual tests for the same materials. In fact, the tests were identical except for a rearrangement of the units in the various series. As in the visual tests the method of recall was oral reproduction. Method of Presentation In the visual presentation of the test material to the subject the following procedure was adopted throughout the experiment: the subject sat at a table opposite the experimenter who was hidden from view by a black cloth screen. The cards containing the units of material were shown to the subject through an exposure apparatus at the rate of one card every two seconds. This rate of exposure, two seconds per unit, was maintained throughout the experiment. Since the cards were fed into the exposure apparatus by hand, a special device was set up to assure as accurate timing as possible. An electrically controlled metronome clicking at the rate of once every two seconds was enclosed in a sound box. The sound of the metronome was conducted to the experimenter by a set of ear-phones. The actual experiment was not begun until the experimenter had had sufficient practice in synchronizing the dropping of the card with the clicking of the metronome. Before the presentation of any series the subject was told how many units the series contained. He was also given a warning signal approximately one second before the presentation of the first unit of the series. In order to make sure that the same