MOTOR SENSORY EFFECTS OF HAPTIC INFORMATION ON IMPLICIT AND EXPLICIT TESTS OF MEMORY

The present experiments explore the components (motor and/or sensory) underlying performance in implicit and explicit tests of memory for haptic information. In the first experiment, the encoding tasks and the test conditions were varied. During the encoding phase half of the subjects were blindfolded and explored real objects with their hands in order to answer questions about object properties (like form) as fast as possible (active exploration). The other subjects performed adequate hand movements without any sensory contact with the objects (motor encoding). At testing, for some subjects the active exploration task was repeated with old and with new objects. Other subjects who did not perform any hand movements based their judgments on sensory impressions only (passive touch). The results demonstrate reliable effects of implicit memory for haptic information, as revealed by faster reaction times to old than to new objects. However, priming effects were only obtained in the active touching test condition. This result was observed for both encoding tasks, that is, even for subjects who had only performed symbolic hand movements at encoding. Thus, the repetition of specific motor processes seems to underly the effects of repetition priming in active touch. In the second experiment, a passive touch paradigm was realized both at encoding and at test (sensory encoding). The priming effects observed under these conditions indicate that sensory processes can be relevant, too. Recognition performance was found to be influenced by other variables than measures of implicit memory. The results are discussed with respect to process-oriented and system approaches to implicit memory.