In addition to the phases of retention and reproduction, there are two important phases of memory, viz.: (3) Recognition of the reproduced impression or experience; and (4) localization of the impression, or its reference to a more or less definite time and place. The recognition of the recalled impression is quite important. It is not enough that the impression be retained and recalled. If we are not able to recognize the recalled impression as having been experienced before, the recollection will be of but little use to us in our thought processes; the purposes of thought demand that we shall be able to identify the recalled impression with the original one. Recognition is really re-cognition--re-knowing. Recognition is akin to perception. The mind becomes conscious of the recalled impression just as it becomes conscious of the sensation. It then recognizes the relation of the recalled impression to the original one just as it realizes the relation of the sensation to its object. The localization of the recalled and recognized impression is also important. Even if we recognize the recalled impression, it will be of comparatively little use to us unless we are able to locate it as having happened yesterday, last week, last month, last year, ten years ago, or at some time in the past; and as having happened in our office, house, or in such-and-such a place in the street, or in some distant place. Without the power of localization we should be unable to connect and associate the remembered fact with the time, place, and persons with which it should be placed to be of use and value to us in our thought processes. RETENTION. The retention of a mental impression in the memory depends very materially upon the clearness and depth of the original impression. And this clearness and depth, as we have previously stated, depend upon the degree of attention bestowed upon the original impression. Attention, then, is the important factor in the forming and recording of impressions. The rule is: _Slight attention, faint record_; _marked attention, clear and deep record_. To fix this fact in the mind, the student may think of the retentive and reproductive phases of memory as a phonographic record. The receiving diaphragm of the phonograph represents the sense organs, and the recording needle represents the _attention_. The needle makes the record on the cylinder deep or faint according to the condition of the needle. A loud sound may be recorded but faintly, if the needle is not properly adjusted. And, further, it must be remembered that the strength of the reproduction depends almost entirely upon the clearness and depth of the original impression on the cylinder; as is the record, so is the reproduction. It will be well for the student to carry this symbol of the phonograph in his mind; it will aid him in developing his powers of memory.