shape memory, property possessed by certain alloys that allows them to return, when heated, to their original shape after having been deformed. This effect results because, as the alloy is deformed, it undergoes a martensitic (or athermal) transformation—a solid-state transition that rapidly changes the crystalline structure of the alloy without thermal activation—that is readily reversed once an appropriate amount of heat is applied. Among the alloys are copper-aluminum-nickel, copper-zinc-aluminum, nickel-titanium, and iron-manganese-silicon. Applications of shape memory include heat-activated fasteners, switches, eyeglass frames, orthopedic devices, teeth braces, and blood clot filters.

memory, in computing: see computer.

memory, in psychology, the storing of learned information, and the ability to recall that which has been stored. It has been hypothesized that three processes occur in remembering: perception and registering of a stimulus; temporary maintenance of the perception, or short-term memory; and lasting storage of the perception, or long-term memory. Two major recognized types of long-term memory are procedural memory, involving the recall of learned skills, and declarative memory, the remembrance of specific stimuli. For long-term memory to occur, there must be a period of information consolidation.

The process of forgetting was first studied scientifically by Hermann Ebbinghaus, a German experimental psychologist, who performed memory tests with groups of nonsense syllables (disconnected syllables without associative connection). Ebbinghaus showed that the rate of forgetting is greatest at first, gradually diminishing until a relatively constant level of retained information is reached. Theories to explain forgetting include the concept of disuse, which proposes that forgetting occurs because stored information is not used, and that of interference, which suggests that old information interferes with information learned later and new information interferes with previously learned information.

In some instances, memory loss is an organic, physiological process. Retrograde amnesia, i.e., the failure to remember events preceding a head injury, is evidence of interrupted consolidation of memory. In anterograde amnesia, events occurring after brain damage—e.g., in head injury or alcoholism—may be forgotten. Memory loss may also result from brain cell deterioration following a series of strokes, cardiovascular disease, or Alzheimer's disease (see dementia).

Physiologically, learning involves modification of neural pathways. PET scans and related studies have shown certain parts of the brain, such as the frontal lobe of the cerebral cortex and a structure called the hippocampus, to be particularly active in recall. Computer models of brain memory are called neural networks. In a study using genetic manipulation, a mouse with enhanced memory capabilities has been produced.

Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel: see under Nobel Prize; for a table of the winners of the prize, see Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel (table).

Year	Recipient(s)
1969	Ragnar Frisch Jan Tinbergen
1970	Paul A. Samuelson
1971	Simon Kuznets
1972	Sir John R. Hicks Kenneth J. Arrow
1973	Wassily Leontief
1974	Gunnar Myrdal Friedrich A. von Hayek
1975	Leonid V. Kantorovich Tjalling C. Koopmans
1976	Milton Friedman
1977	James E. Meade Bertil Ohlin
1978	Herbert A. Simon
1979	Sir Arthur Lewis Theodore W. Schultz
1980	Lawrence R. Klein
1981	James Tobin
1982	George J. Stigler
1983	Gerard Debreu
1984	Richard Stone
1985	Franco Modigliani
1986	James M. Buchanan
1987	Robert M. Solow
1988	Maurice Allais
1989	Trygve Haavelmo
1990	Harry M. Markowitz William F. Sharpe Merton H. Miller
1991	Ronald H. Coase
1992	Gary S. Becker
1993	Robert W. Fogel Douglass C. North
1994	John F. Nash John C. Hasranyi Reinhard Selten
1995	Robert E. Lucas, Jr.
1996	William S. Vickrey James A. Mirrlees
1997	Robert C. Merton Myron S. Scholes
1998	Amartya Sen
1999	Robert A. Mundell
2000	James J. Heckman Daniel L. McFadden
2001	George A. Akerlof A. Michael Spence Joseph E. Stiglitz
2002	Daniel Kahneman Vernon L. Smith
2003	Robert F. Engle Clive W. J. Granger
2004	Finn E. Kydland Edward C. Prescott
2005	Robert J. Aumann Thomas C. Schelling
2006	Edmund S. Phelps

Temporary computer storage used for quick retrieval of data in order to increase processing speed. The cached data can be stored in a reserved area of RAM, a special cache chip (separate from the CPU) that provides faster access than RAM, or on the disk drive. By keeping frequently accessed data in a rapidly accessible place, the computer can respond quickly to requests for those data without having to perform time-consuming searches of RAM or hard drives. Since a “stale” cache will contain data that have been superseded by later information, the cached data must be refreshed periodically.

Learn more about cache with a free trial on Britannica.com.

In digital computers, a physical device used to store such information as data or programs on a temporary or permanent basis. Most digital computer systems have two types of memory, the main memory and one or more auxiliary storage units. In most cases, the main memory is a high-speed RAM. Auxiliary storage units include hard disks, floppy disks, and magnetic tape drives. Besides main and auxiliary memories, other forms of memory include ROM and optical storage media such as videodiscs and compact discs (see CD-ROM).

Learn more about memory with a free trial on Britannica.com.