The option View : Special : Leeches can be used to locate all elements that cause problems in the learning process. This option makes use of the element filter dialog box that can be used to find all element meeting a specific set of criteria such as the number of repetitions, number of memory lapses, length of the current interval, status (memorized, pending, or dismissed), type (item or topic), etc.

The purpose of locating leeches is to reedit most intractable items with a view to applying appropriate mnemonic techniques. Alternatively you can reset elements (e.g. to deal with them later), dismiss them (to use them only as reference, e.g. with Search : Find elements), or simply delete them.

Important!
To maximize the effectiveness of the learning process, you should learn to use View : Leeches and periodically remove from your collection most intractable and badly structured material

The following fields can be used to select the minimum and the maximum values that fall into the range defined for difficult elements:

• Repetitions - number of repetitions made with a given element. This is not a good criterion for defining leeches and it turned off by default
• Lapses - number of times a given element was forgotten. This is the primary field for defining leeches. For example, if you want to find all elements that have been forgotten at least 5 times, set Minimum at five and Maximum at 100 (or other value that is greater than maximum number of lapses)
• Interval - number of days between the last repetition and the next repetition. You might want to limit intervals to some value (e.g. 1 to 50 days) to account for the fact that even elements that have been forgotten many times may be disregarded as leeches if they had passed a certain length of interval without being forgotten
• Last repetition - number of days between the first day of the learning process and the last repetition date (see Tools : Workload to view day numbering). This field should not be used in searching for leeches
• Next repetition - number of days between the first day of the learning process and the next repetition date. This field should not be used in searching for leeches
• A-Factor - value of A-Factor assigned to a given element. This is not a good criterion for defining leeches. If you want to use if, choose the lower range of A-factors (e.g. from 1.3 to 1.5)
• Forgetting index - probability of forgetting a given element during each repetition. The forgetting index is set by the user and is by no means a reflection of element difficulty. You might use it however to locate items of lower priority (e.g. as defined by a higher forgetting index). By using the forgetting index field you might sharpen the leech criteria for elements that are of lower priority. For example, you might decide to reset all leeches and be more strict with resetting elements to which you assigned a higher forgetting index
• Ordinal number - ordinal number assigned to a given element. The ordinal number is set by the user and is by no means a reflection of element difficulty. You might use it however to locate items of lower priority (e.g. as defined by a higher ordinal numbers). This way you might sharpen the leech criteria for elements that are of lower priority

If you do not want to use a given criterion, uncheck the check-box associated with a given field. If you do want to use it, check the check-box and specify appropriate minimum and maximum values.

The fields Type, Status, Item, Topic and Memorized should not be used in searching for leeches. By definition, all leeches are memorized items.

Once you click OK, all leeches meeting the specified criteria will be found and will be displayed in a browser.

Leech parameters are stored between sessions in the file <supermemo directory>\<systems>\<collection name>\ks.ini in the section [Leech].