Material-specific processes in tactile short-term memory

-· ;..meaning ligh wave patt memory preperceptual synthesized T ;,visual ~visual rn storage . memory detection perception conception Figure 1. Short-term memory systems (¥assaro, 1973). To test this model, YDssaro (1973) used same-different reaction time tasks.. The subjects were presented with two spoken letters, and were to decide if they had the same or different names. The indepe_ndent variable was whether the two letters were presented by the same or different speakers. Massaro found a faster. reaction time on both the same and different name trials when the same speaker articulated the ·letters. This faster reaction time was independent of a delay between the presentation of the two letters. Massaro suggests the subjects retained the experimenter's voice in synthesized auditory memory and used that inf'ormatj_on to facilitate recognition of the second letter. 4 Massaro found a similar resu1t for visually presented letters. Reaction times were approximately 80 msec faster with physical matches (i.e., letters printed in the same way) than with name matches under a no-delay condition when the letters were printed differently. When an interval was interpolated between the two stin1ulus letters, the reaction times were the same. Apparently, when a delay is introduced subjects compare the letters on a name basis-; utilizing materialspecific memory. Beller (1967) also found that the response ~ime to physically identical letters was faster than to physically different letters with the same name· (i.e.,~ and~)· Posner & Mitchell (1967) found similar results. Tnus, the faster reaction time to physically· match letters, as gpposed to naming them, points to serial processing .of' the informatio~ in this memory. sys.tem, from modality-s:peci:fic to •· ~aterial-specific memory. If the subjects are instructed to say the names of the letters aloud, then the reaction times between physically matching and naming are identical. That is, it takes just as long to recognize three same and three different letters (Ingalls, 1974). Thus, if the instructions are to internally decide sa~e or different, modality-specific memory is tapped, and the physical attributes are compared. If the instructions are to speak the letter names and decide if they are the same or different, material-specific memory is tapped, and the semantic attributes are compared. V.i.assaro (1975, p. 13) also notes that there is probably some overlap of these systems. For instance, modality-specific memory may eliminate alternatives to what is heard (such as shoes or choose). Mlterial-specific memory may note that only shoes is. correct· semantically (as in "Take off your shoes"} 5 and feeds back that information into modality-specific store so the word is heard as shoes. Although the information usually goes from percept to meaning, conceptual information may modify perceptual experience. Massaro (1973) also presented evidence for separate visual and auditory memory stores. Subjects were given a list·of first auditory digits, and then visual letters for one presentation. Since STMhas a limited capacity, the auditory list should have caused a decrease in the recollection of the visual list. H9wever, the correct recall for each list was identical. This then suggests the existence of modalityspecific STM; a separate, independent memory store for each sensory modality • .' M9.ssaro also noted that in a shadowing task, where subjects first remember a letter ~resented visually or orally, and then repeat back the auditory list, auditory shadowing interfered with the recall of the auditory list much more than the visual shadowing did. Short-term memory can then be discussed in terms of two systems: Modality-speci~ic, such as visual and auditory memory, and materialspecific, such as verbal and nonverbal memory. There are several behavioral differences that distinguish these systems. Forgetting is very rapid in modality-specific memory (about 5-15 seconds), and is as rapid for filled as fur unfilled retention intervals if the interpolated task is in a modality'different from.the one under observation. Events occuring in other sensory modalities do not affect the modalityspecific memory of a particular modality. Events in the same modality as a given sensory storage system will interfere with it and cause it to be lost (Sch~n, et al., 1973). Verbal STM, due to the higher