An experimental investigation of memory span.

The present study is concerned with the relative constancy of the memory span.In the literature there is no definite evidence as to whether memory span is general or specific, i.e., whether the span of an individual remains constant relative to that of the other members of the group in spite of the variations due to the influence of other factors.In this investigation two factors were varied at different times, namely, the type of material and the sensory avenue of presentation.The object was to investigate the constancy of the individual in relation to the group under these two conditions.At the same time the data also yield information on the absolute constancy of the memory span.In the earlier literature the general belief was that there was a constant absolute size of memory span, i.e., that the size of the span did not vary with the material presented.Blankenship (i), in a recent summary of the literature, presents evidence to prove that the absolute size of the span varies from material to material.The present study lends further evidence to this latter conclusion.It may be noted in passing that should there be an absolute constancy, that is, should the size of the memory span be independent of the type of material then the question of relative constancy would be automatically solved, and memory span would of necessity be general rather than specific. PLAN OF THE EXPERIMENT Materials and Method of RecallTests were constructed with ten different kinds of material.The materials are listed below with explanations as to the procedure followed in constructing the tests.* The writer wishes to express his appreciation to Dr. H. A. Carr, Dr. F. A. Kingsbury, and Dr. L. L. Thurstone for their guidance and assistance during the course of this study.He also wishes to thank Mr. Ledyard R. Tucker for his suggestions of procedure in the factorial analysis on which the latter part of the study is based.However, in order to clarify the procedure and the general et-up of the experiment a few wordi of explanation are given on the terminology used to describe the tests.Each test was composed of a variable number of units.In the digit test, for example, each digit was a unit; in the sentence test each sentence was a unit, etc.The units were organized into series of varying lengths.In some tests the minimum length of a series was one unit; in some tests the maximum length was thirteen units.The presentation of a series to the subject constituted a trial.In all the tests except two each unit was typed on a separate 3" X 5" card.In the two remaining tests 3" X 5" cards were also used.However, in one of the tests, the test of Geometrical Designs, each unit was drawn on a card rather than typewritten.In the other test, the test of Colors, each unit was pasted on a separate card.Digits.-In the digit test, as already indicated, each digit was a unit.Ten series of four units were constructed, ten series of five units, ten series of six units, etc., up to and including ten series of thirteen units.In all other tests, likewise, ten series were constructed for each unit length.In constructing the various series for the digit* the usual precautions were observed.An attempt was made to avoid common associations such as historical dates, the current year, etc.No digit was placed next to one immediately following or preceding it in the usual order of counting; e.g., the number seven was never placed after six or eight.No digit was repeated in any one series except where there were more than nine units to the series.The method of recall of the series of digits was oral reproduction.This method of recall was used for all of the tests except the test of Memory for Commissions.At the conclusion of each series the subject was supposed to repeat the digits in the order of their appearance in the series.Nonsense Syllables.-Eachnonsense syllable constituted a unit.Series for this test varied in length from one to six units inclusive.All of the nonsense syllables used in this test were chosen from Glaze's (3) list of syllables having associational values ranging from 40 percent to 53.33 percent.In reproducing any given series the subject was instructed to spell out the three letters of each nonsense syllable rather than to pronounce the syllable.Consonants.-Each consonant constituted a unit.The series varied in length from four to thirteen units inclusive.In constructing the series the same general rule was followed as for digits, with the additional consideration that no series contained the same unit twice.Likewise, in recall the procedure was the same as for digits.Geometrical Designs.-Thefollowing figures or designs were used: oval, triangle, square, spade, heart, diamond, trapezoid, circle and semi-circle.Each design constituted a unit.The series varied in length from four to nine units inclusive.The designs were drawn in India ink on 3" X 5" cards.All of the designs were made as nearly equivalent in area as possible.The area per design was approximately one-half square inch.In recalling any series the subject was supposed to repeat the names of the designs in their proper order.Colors.-The following colors were used: red, orange, yellow, green, blue, white, purple, black and gray.Strips of color one-fourth by one inch were cut from sheets of paper ordinarily used in color vision experiments.Each strip was pasted on a card 3" X 5" to constitute a unit.The series varied in length from four to ten units inclusive.Again, the subject reproduced orally the names of the colors in the order of their appearance.Concrete Words.-Each unit was a four letter concrete noun, e.g., goat, hand, doll, etc.The series varied in length from four to ten units inclusive.Special care was taken to avoid alphabetical arrangement of the units and obvious associations such as