Single-trace fragility theory of memory dynamics

Abstract

In single-trace fragility theory, forgetting is produced by two factors, time and interference. Memory traces are assumed to have two partially coupled dynamic properties, strength and fragility. Strength determines the probability of correct recall and recognition, while fragility determines the susceptibility of the trace to the time-decay process but not to the interference process. Consolidation is assumed to be a continual reduction in the fragility of the memory trace rather than any change in strength or availability. Decreasing fragility accounts for the continually decreasing forgetting rate, the temporal character of retrograde amnesia and recovery therefrom, and the type of internal clock necessary for nonassociative recency judgments. Data are presented to indicate that interference is independent of the interval between original and interpolated learning, that nonassociative recency discriminability approaches a limit at about 30 min, and that the decay rate of long-term retention in amnesic patients is the same as in normal Ss.For some years now it has been fashionable to assume at least two d~namically distinct memory traces or processes, short term or long term. An enormous number of memory phenomena have been interpreted as providing support for the two-trace hypothesis. I think that all of these phenomena are equally consistent with a single-trace hypothesis, though this single trace must be viewed as undergoing a consolidation process that progressively reduces its rate of forgetting and its susceptibility to amnesic agents with increasing trace age.Wickelgren (1973) discussed all the frequently cited psychological evidence for distinguishing two dynamic types of memory traces and demonstrated that all of this evidence was equally consistent with a single-trace theory, with three exceptions. The three phenomena alleged to support the distinction between short-term and long-term memory were (a) the different forms of retention function, (b) the different effects of similarity on storage interference (as measured by recognition tests), and (c) evidence from amnesic patients such as the classic H. M. of Scoville and Milner (1957). I now believe that a single-trace theory can account for even these three phenomena and one such theory is described in this paper. Instead of two traces, the theory proposes two mechanisms that produce decay of the memory trace: (a) a storage interference process dependent on the processing of subsequent similar material and (b) an interference-free time-decay process. The theory also contains a new hypothesis regarding consolidation based on the assumption that memory traces have two partially coupled dynamic properties, strength and fragility. Greater strength implies more accurate recognition and recall. Greater fragility implies greater *This research was supported by Grant 3-0097 from the National Institute of Education, by Grants MH 00890 and MH 17958 from NIMH, and by Contract F 44620-73-e-0056 from ARPA to Ray Hyman. I thank Adam Reed for influencing me to seri...

The psychology of intelligence analysis: Drivers of prediction accuracy in world politics.

“…To the data, Wetzler and Sweeney fitted a power function that in many investigations (e.g., Crovitz & Schiffman, 1974;Rubin & Wenzel, 1996;Rubin, Wetzler, & Nebes, 1986) has been shown to capture the distribution of memories across the life span. As discussed by Rubin and Wenzel (1996), the power function (e.g., Wickelgren, 1974Wickelgren, , 1975 implies that equal ratios of time (t 1 /t 2 ϭ t 3 /t 4 ) will result in equal ratios of recall (recall 1 /recall 2 ϭ recall 3 /recall 4 ). Thus, for example, if Time 2 recall was 90% of Time 1 recall, then Time 4 recall would be 90% of Time 3 recall (i.e., assuming equal ratios of time).…”

Discrete-Slots Models of Visual Working-Memory Response Times

“…In particular, Donkin and Nosofsky (2012a) conducted a short-term proberecognition experiment involving the sequential presentation of memory-set items. In modeling the choice and RT data from that experiment, Donkin and Nosofsky (2012a) obtained evidence that the "memory strength" of the items decreased as a power function of their lag of presentation (see also Anderson & Schooler, 1991;Wickelgren, 1974;Wixted & Ebbesen, 1991). In the context of the present types of visual WM tasks, one might imagine an analogous process in which the observer shifts covert visual attention across the memoryset items, with more recently attended items having greater memory strength.…”

Spacing and repetition effects in human memory: application of the SAM model

“…Reed (1977) showed that the Markov model of Young (1971) performed more or less similar as the present model (leading to a χ 2 -value of 49.3, df = 18). However, a model based on Wickelgren's strength-resistance theory (Reed, 1976;Wickelgren, 1972Wickelgren, , 1974aWickelgren, , 1974b) did perform substantially better, leading to χ 2 values between 24 and 30 depending on the exact assumptions of the model. The basic reason for this superior fit seems to be due that the Reed model is capable of fitting the initial decrease for short retention intervals when the spacing interval increases from 0 to 3 s (see the top curve in the left panel of Fig.…”