Repetition priming refers to the finding that an initial presentation of a stimulus influences the way in which an individual will respond to that stimulus when it is presented at a later time. The response to a specific item that has been encountered recently (a word, for example) will be faster and more accurate compared to another item that has not. This often coincides with a reduction in neural activity in cortical regions, as measured by functional magnetic resonance imaging, relative to novel stimuli, a phenomenon known as repetition suppression. Unlike other types of priming, including indirect and semantic priming, which persist for only a few seconds, repetition priming has been shown to last for intervals of up to several weeks.
Repetition priming assesses implicit memory (or non-declarative memory), a memory system that does not require conscious awareness. For example, the faster response to a stimulus resulting from repetition priming will occur even if the individual does not consciously recall seeing that particular stimulus. A number of studies on amnesic patients with damaged diencephalic and/or limbic structures are still capable of demonstrating repetition priming, despite having severe difficulty remembering recent experiences.
A number of models have put forward to explain repetition priming. The major ones are presented below.
The modification approach proposes that the improvement in performance observed in repetition priming is due to the modification of pre-existing perceptual or semantic representations upon the initial presentation of a stimulus. Consequently, the efficiency of neural processing in the relevant brain certain regions are improved, facilitating responses upon subsequent presentations of the same stimuli. The degree of facilitation is thought to be largely dependent on the degree of overlap between the mental processes involved during both presentations of the stimulus, perhaps owing to the extent of overlap between the neural pathways engaged. This is sometimes referred to as the 'greasing the tracks' phenomenon as the initial presentation of the stimulus serves to 'grease the tracks' and therefore facilitate the response if the same tracks are used when the stimulus is presented again.
An alternative theory proposed for repetition priming is the episodic model, which explains that repeated presentations of a stimulus alters behaviour through the retrieval of stimulus-response (S-R) bindings. According to this theory, the initial presentation of a stimulus and the response made to it are encoded together in an S-R binding. When the stimulus is presented again, the S-R binding is retrieved and may affect performance. If the retrieved binding is congruent to the required response, performance is improved.
S-R learning dominates in long-lag visual classification experiments, with little evidence for perceptual or conceptual contributions. The results alluded to the presence of multiple levels of response representation within S-R bindings, with separate contributions from motor actions, more abstract decisions and task-dependent classifications. Moreover, it has been found that multiple levels of format-specific stimulus representations may also be encoded in S-R bindings.
- Grill-Spector, K., Henson, R., & Martin, A. (2006). Repetition and the brain: Neural models of stimulus-specific effects. Trends in Cognitive Sciences, 10, 14–23.
- Neely, J. (1991). Semantic Priming Effects in Visual Word Recognition: a Selective Review of Current Findings and Theories. In Task Processes in Reading: Visual Word Recognition. Edited by Besner D, Humphreys G. Hillsdale, NJ: Erlbaum; 1991:264-336.
- Schacter, D. (1987). Implicit Memory: History and Current Status. J Exp Psychol [Learn Mem Cogn]. 13:501-518.
- Squire, L. (1992). Memory and the Hippocampus: a Synthesis From Findings With Rats, Monkeys, and Humans. Psychol Rev. 99:19-231.
- Henson, R. (2003). Neuroimaging studies of priming. Progress in Neurobiology, 70, 53–81.
- Kolers, P. A., & Roediger, H. L. (1984). Procedures of mind. Journal of Verbal Learning and Verbal Behavior, 23, 425–449.
- Roediger, H. L., & McDermott, K. B. (1993). Implicit memory in normal human subjects. In F. Boller & J. Grafman (Eds.), Handbook of neuropsychology (Vol. 8, pp. 63–131). Amsterdam: Elsevier.
- Logan, G. D. (1990). Repetition priming and automaticity: Common underlying mechanisms? Cognitive Psychology, 22, 1–35.
- Hommel, B. (1998). Event ﬁles: Evidence for automatic integration of stimulus-response episodes. Visual Cognition, 5, 183–216.
- Horner, A. J., & Henson, R. N. (2009). Bindings between stimuli and multiple response codes dominate long-lag repetition priming in speeded classification tasks. Journal of Experimental Psychology: Learning, Memory, and Cognition, 35(3), 757–779.
- Horner, A. J., & Henson, R. N. (2011). Stimulus–Response bindings code both abstract and specific representations of stimuli: Evidence from a classification priming design that reverses multiple levels of response representations. Memory & Cognition, 39, 1457–1471.