That experiences influence subsequent behaviour is evidence of an obvious but nevertheless remarkable activity called remembering. Learning could not occur without the function popularly named memory. Constant practice has such as effect on memory as to lead to skilful performance on the piano, to recitation of a poem, and even to reading and understanding these words. So-called intelligent behaviour demands memory, remembering being a primary requirement for reasoning. The ability to solve any problem or even to recognize that a problem exists depends on memory. Typically, the decision to cross a street is based on remembering many earlier experiences.
Practice (or review) tends to build and maintain memory for a task or for any learned material. Over a period of no practice what has been learned tends to be forgotten; and the adaptive consequences may not seem obvious. Yet, dramatic instances of sudden forgetting can be seen to be adaptive. In this sense, the ability to forget can be interpreted to have survived through a process of natural selection in animals. Indeed, when one's memory of an emotionally painful experience lead to serious anxiety, forgetting may produce relief. Nevertheless, an evolutionary interpretation might make it difficult to understand how the commonly gradual process of forgetting survived natural selection.
In thinking about the evolution of memory together with all its possible aspects, it is helpful to consider what would happen if memories failed to fade. Forgetting clearly aids orientation in time, since old memories weaken and the new tend to stand out, providing clues for inferring duration. Without forgetting, adaptive ability would suffer, for example, learned behaviour that might have been correct a decade ago may no longer be. Cases are recorded of people who (by ordinary standards) forgot so little that their everyday activities were full of confusion. This forgetting seems to serve that survival of the individual and the species.
Another line of thought assumes a memory storage system of limited capacity that provides adaptive flexibility specifically through forgetting. In this view, continual adjustments are made between learning or memory storage (input) and forgetting (output). Indeed, there is evidence that the rate at which individuals forget is directly related to how much they have learned. Such data offers gross support of contemporary models of memory that assume an input-output balance.

67. From the evolutionary point of view, ________.
[A] forgetting for lack of practice tends to be obviously inadaptive
[B] if a person gets very forgetful all of a sudden he must be very adaptive
[C] the gradual process of forgetting is an indication of an individual's adaptability
[D] sudden forgetting may bring about adaptive consequences

68. According to the passage, if a person never forgets, ________.
[A] he would survive best
[B] he would have a lot of trouble
[C] his ability to learn would be enhanced
[D] the evolution of memory would stop

69. From the last paragraph we know that ________.
[A] forgetfulness is a response to learning
[B] the memory storage system is an exactly balanced input-output system
[C] memory is a compensation for forgetting
[D] the capacity of a memory storage system is limited because forgetting occurs

70. In this article, the author tries to interpret the function of ________.
[A] remembering
[B] forgetting
[C] adapting
[D] experiencing
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