Priming is a form of memory for specific factual and episodic information that depends on automatic retrieval processes and does not need to involve feeling of familiarity for what is remembered.
Priming also has been described as the effect of prior exposure to a specific stimulus on subsequent ability to identify that stimulus.
Priming generally results in improved performance on a task, with higher response accuracy and faster response time.
Types of Priming
Two different types of priming have been distinguished:
perceptual priming, which is based on physical or perceptual features and operates at a pre-semantic level, and
Semantic priming also known as (conceptual priming), is based on semantic or associative resemblances between stimuli and is mediated by semantic memory.
Priming can be either direct or indirect. It is direct when the benefit is obtained through presentation of the same stimulus. Indirect priming is obtained through presentation of different stimuli that share perceptual, associative, or semantic features.
Evaluation of Priming
Evaluation of priming is performed in two phases: study – and test phase.
During the study phase, a set of stimuli, e.g. comprising of words or drawings, is presented to the subject.
After a delay, test phase is performed, in which another set of items is presented. This set comprises target items that are identical or connected to the items viewed during the study phase, as well as distracters that were not presented previously.
The priming effect is the difference between performance in response to target items and distracters in the test phase.
Stem completion is a task used to measure perceptual or conceptual (semantic) priming. During the study phase, the subject executes a task on a set of stimuli (count the vowels of words in the perceptual version or make the sentence with the words in the semantic version). In the test phase, the subject is asked to complete a list of word stems with the first word that comes to mind.
Priming is the tendency to complete the stems with the words presented in the study phase. Perceptual priming Opens in new window can also be measured by presenting items, usually drawings, with progressive degrees of perceptual degradation or masking. In such tasks, subjects will tend to identify the items at a higher degree of degradation or masking in the test phase than in the study phase (Tulving and Schacter 1990).
Studies on healthy subjects have indicated that priming depends on neocortical regions. Perceptual priming has often been related to activation modulations in the visual cortex and semantic priming appears to preferentially involve the left inferior frontal cortex and the anterior temporal lobe (Henson 2003).
These regions are distinct from the medial temporal and diencephalic regions affected in the amnesic syndrome. In fact, preserved priming effects have repeatedly been observed in amnesic patients. However, the medial temporal lobes and the diencephalic structures are responsible for the formation of associations between stimuli, which may explain why many amnesic patients fail on the priming tasks that require complex associations (Paller and Mayes 19970.)
Patients suffering from Alzheimer’s disease Opens in new window also show preservation of perceptual priming, but they tend to develop semantic priming deficits. These deficits have been associated with degeneration of the temporo-parietal association cortex (Gabrieli et al. 1994).
