Three hundred and ninety two high school graduates were tested for memory of names and portraits of classmates selected from yearbooks. The retention interval since graduation varied from 2 wk to 57 yr. Performance was adjusted by multiple regression procedure to control the effects of various conditions that influence original learning, such as class size, and other conditions that influence rehearsal of the material, such as attendance at class reunions.The cross-sectional approach illustrated in this study is discussed as an alternative to the traditional longitudinal approach to the study of memory. The cross-sectional adjustment approach sacrifices laboratory control over the conditions of original learning, but permits extension of investigations to conditions that significantly affect learning and memory but that cannot be adequately or conveniently manipulated in the confines of the laboratory. Examples are a greater range of learning material, of motivational conditions, of context effects, and most significantly of acquisition time and retention time. Since most of the vital information in the memory store is learned and retained over periods much longer than those which are investigated in the laboratory, available generalizations based on laboratory findings may be inadequate or inapplicable to these area of knowledge. The cross-sectional ap-

Wickens for providing equipment and facilities and Leni Rosenfield for assistance in the collection of the data.2 Requests for reprints should be sent to M.

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