Saul Sternberg

High-Speed Scanning in Human Memory

When subjects judge whether a test symbol is contained in a short memorized sequence of symbols, their mean reaction-time increases linearly with the length of the sequence. The linearity and slope of the function imply the existence of an internal serial-comparison process whose average rate is between 25 and 30 symbols per second.

Memory scanning: New findings and current controversies

Introduction : the reaction-time method in memory research. The item-recognition paradigm. Early findings and interpretations : the exhaustive-search model. Generalizations and extensions of paradigm and phenomenon. Findings that challenge the model or limit its scope, and what to do about them. Alternative models of the comparison process. 6. I Self-terminating search. 6.2 Trace-strength discrimination. 6.3 Parallel comparisons. New findings. 7.1 The translation effect. 7.2 Partial selectivity of search. 7.3 7.4 7.5 Summary. References Relation between search structure and search rate. Exhaustive search in long-term memory. Relation between memory search and the memory span.

6 – The Latency and Duration of Rapid Movement Sequences: Comparisons of Speech and Typewriting

Publisher Summary This chapter discusses the temporal patterns of rapid movement sequences in speech and typewriting and what these patterns might mean in relation to the advance planning or motor programming of such sequences. The chapter discusses response factors that affect the time to initiate a prespecified rapid movement sequence after a signal when the goal is to complete the sequence as quickly as possible as well as how such factors affect the rate at which movements in the sequence are produced. The response factor of central interest is number of elements in the sequence. The effect of the length of a movement sequence on its latency is based partly on the possibility that it reflects a latency component used for advance planning of the entire sequence: The length effect would then measure the extra time required to prepare extra elements. The idea that changes in reaction time might reflect changes in sequence preparation in this way proposed that simple reaction time increased with the number of elements in a sequence of movements made with one arm. A part of the reaction time includes the time to gain access to stored information concerning the whole sequence: a process akin to loading a program into a motor buffer, with sequences containing more elements requiring larger programs, and larger programs requiring more loading time.

Separate modifiability, mental modules, and the use of pure and composite measures to reveal them.

How can we divide a complex mental process into meaningful parts? In this paper, I explore an approach in which processes are divided into parts that are modular in the sense of being separately modifiable. Evidence for separate modifiability is provided by an instance of selective influence: two factors F and G (usually experimental manipulations) such that part A is influenced by F but invariant with respect to G, while part B is influenced by G but invariant with respect to F. Such evidence also indicates that the modules are functionally distinct. If we have pure measures MA and MB, each of which reflects only one of the parts, we need to show that MA is influenced by F but not G, while MB is influenced by G but not F. If we have only a composite measure MAB of the entire process, we usually also need to confirm a combination rule for how the parts contribute to MAB. I present a taxonomy of separate-modifiability methods, discuss their inferential logic, and describe several examples in each category. The three categories involve measures that are derived pure (based on different transformations of the same data; example: separation of sensory and decision processes by signal detection theory), direct pure (based on different data; example: selective effects of adaptation on spatial-frequency thresholds), and composite (examples: the multiplicative-factor method for the analysis of response rate; the additive-factor method for the analysis of reaction time). Six of the examples concern behavioral measures and functional processes, while four concern brain measures and neural processes. They have been chosen for their interest and importance; their diversity of measures, species, and combination rules; their illustration of different ways of thinking about data; the questions they suggest about possibilities and limitations of the separate-modifiability approach; and the case they make for the fruitfulness of searching for mental modules.

Retrieval of contextual information from memory

When Ss name the item that follows a test item in a short recently memorized list, their mean reaction-time (

Motor Programs and Hierarchical Organization in the Control of Rapid Speech

\overline {\rm RT}

Modular processes in mind and brain

) increases linearly with list length. The linearity and slope of the function, and the effect of the test item’s serial position, imply that the test item is located in the memorized list by an internal self-terminating scanning process whose average rate is about four items/sec.

Perception, Production, and Imitation of Time Ratios by Skilled Musicians

We provide a summary of our recent research on the control of rapid action sequences in speech production, emphasizing findings about the advance planning and hierarchical organization of such utteran

The meaning of additive reaction-time effects: some misconceptions

One approach to understanding a complex process starts with an attempt to divide it into modules·, sub- processes that are independent in some sense, and have distinct functions. In this paper, I discuss an approach to the modular decomposition of neural and mental processes. Several examples of process decomposition are presented, together with discussion of inferential requirements. Two examples are of well-established and purely behavioural realizations of the approach (signal detection theory applied to discrimination data; the method of additive factors applied to reaction-time data), and lead to the identification of mental modules. Other examples, leading to the identification of modular neural processes, use brain measures, including the fMRI signal, the latencies of electrophysiological events, and their amplitudes. Some measures are pure (reflecting just one process), while others are composite. Two of the examples reveal mental and neural modules that correspond. Attempts to associate brain regions with be- haviourally defined processing modules that use a brain manipulation (transcranial magnetic stimulation, TMS) are promising but incomplete. I show why the process-decomposition approach discussed here, in which the criterion for modularity is separate modifiability, is superior for modular decomposition to the more frequently used task comparison procedure (often used in cognitive neuropsychology) and to its associated subtraction method. To demonstrate the limitations of task comparison, I describe the erroneous conclusion to which it has led about sleep deprivation, and the interpretive difficulties in a TMS study.

In Defence of High-Speed Memory Scanning:

We have described our exploration of the judgment, production, and imitation of fractions of a beat by skilled musicians, illustrating our findings with data from violinist and conductor Paul Zukofsky. For small fractions we found systematic and substantial errors. In the judgment task small stimulus fractions are associated with names that are too large (overestimation). In both production and imitation tasks the fractions produced were too large (overproduction, overimitation). A summary of our findings and of the expectations they violate is provided in Figure 7. The temporal patterns we used are perhaps the simplest that qualify as rhythms, incorporating just a beat interval and a fraction. The phenomena we discovered in relation to these simple patterns, and their implications for underlying mechanisms, must be considered in attempts to understand the perception and production of more complex rhythms, as in actual music. We explored and rejected several plausible explanations for the overestimation and overproduction of small fractions. Although we have as yet no satisfactory explanations of the errors themselves, relations among the errors have powerful implications for human timing mechanisms. The relation between the errors in judgment and production requires us to reject a feedback model of production, in which a subject uses the same processes as in the judgment task to evaluate and adjust his performance in the production task. An explanation of the inconsistency between judgment and production seems most likely to lie in a change in time perception induced by the production task. Together with the existence of systematic errors in judgment, the equality of the errors in production and imitation argues that imitation is not accomplished by concatenating all the processes used in judgment and production. Our results are instead consistent with a model containing four internal transformation processes, in which judgment and production share no process, but do involve the same internal-fraction representation, and in which imitation shares one process with judgment and another with production.