:orphan:

trace
*****

.. note::

  Memory traces are only implemented in the *Stimulus-response learning* and *Guided associative learning* mechanisms.

Specifies the decay factor of fading memory traces. The value is a number between 0 and 1. The higher value, the longer the
memory trace of each stimulus stays with the subject. A low value means it fades fast. The default is 0.

The value of the parameter ``trace`` is used in :ref:`the decision function<the-decision-function>`.

Syntax
------

::

  trace = v

where ``v`` is a :ref:`scalar expression<scalar-expressions>`.

Description
-----------

``trace = v`` sets the decay factor to ``v``.


Examples
--------

::

  trace = 0.5

sets the decay factor to 0.5.

::

  @variables x = 0.5
  trace = x + 0.1

sets the decay factor to 0.6.