Cross-task cross talk in memory and perception

The application of the additive factors method depends on finding factors that selectively influence processing stages. When all the processes for a task are in series, a factor directly influencing a process might change its output and thereby have indirect influence on succeeding processes. We investigate whether such indirect influence is possible between processes associated with different tasks being performed together. In two dual-task memory scanning and arithmetic experiments with digits as the stimuli for both tasks, information relevant for only one of the tasks nonetheless affected performance of the other. When the same digit was relevant for the two tasks, cross-task facilitation and interference were observed in some cases. Displaying the same digit for both tasks led to relatively fast response times, paralleling the effect of flankers in the response competition paradigm. But repetition of digits in memory slowed responses. It is suggested that the need for control processes to keep task information segregated is responsible for the pattern of effects.     

A multinomial processing tree model for degradation and redintegration in immediate recall

When items are presented for immediate recall, a verbal trace is formed and degrades quickly, becoming useless after about 2 sec. The span for items such as digits equals the number of items that canbe pronounced in the available time. The length of the items affects span by affecting pronunciation rate. Other properties, such as phonological similarity and lexicality, can affect span without affecting pronunciation rate. These properties change the trace's useful lifetime by affecting redintegration. An analogy is drawn between trace reconstruction and repair of errors in speech. When a trace is degraded, one process attempts to form a phoneme string, and another process attempts to form a word. The two processes are autonomous and can be selectively influenced by lexicality and phonological similarity. The resulting processing tree models make simple predictions that depend on whether or not the influenced processes are sequential. The results are illustrated with data from experiments by Besner and Davelaar (1982).     

Syntactic and semantic contributions to sentence comprehension in agrammatism

Five aphasic subjects, who demonstrated agrammatic speech, and eight control subjects were presented with a sentence-picture matching task in which the factors of syntactic complexity, semantic reversibility, and sentence plausibility were independently varied. A subset of the sentences was patterned after that presented by A. Caramazza and E. Zurif (1976, Brain and Language, 5, 572-583) who concluded that Broca's aphasics rely on semantic constraints instead of syntactic information for sentence comprehension. Our aphasic subjects showed the same pattern of performance on this subset of sentences. However, the results from the full set of sentence materials we tested show that the aphasic subjects could perform some sentence level syntactic analyses, even when syntactic information conflicted with semantic constraints. The aphasic subjects correctly interpreted most active and passive sentences. They failed, however, to assign thematic roles and adjectives in center-embedded relative sentences, and instead relied on nonsyntactic information. These results show that both semantic and syntactic information contributed to sentence comprehension in the aphasic subjects we tested, in contrast to previous claims that syntactic and semantic processes are completely dissociated in this population.     

Silent reading rate and memory span

This paper reports two experiments concerned with the form of the linear function relating memory span to pronunciation rate. Experiment 1 asked whether the intercept of the equation is attributable to an interaction between modality, word‐length, and serial position. The results lead us to reject this possibility. Experiment 2 examined the shape of the span function for visual presentation of lists read aloud or silently. The results show that the intercept of the span function disappears for silent presentation but not for aloud presentation. The results are discussed in terms of a balance between two opposing effects of word‐length.     

Additive factors and stages of mental processes in task networks

To perform a task a subject executes mental processes. An experimental manipulation, such as a change in stimulus intensity, is said to selectively influence a process if it changes the duration of that process leaving other process durations unchanged. For random process durations a definition of a factor selectively influencing a process by increments is given in terms of stochastic dominance (also called “the usual stochastic order”). A technique for analyzing reaction times, Sternberg’s Additive Factor Method, assumes all the processes are in series. When all processes are in series, each process is called a stage. With the Additive Factor Method, if two experimental factors selectively influence two different stages by increments, the factors will have additive effects on reaction time. An assumption of the Additive Factor Method is that if two experimental factors interact, then they influence the same stage. We consider sets of processes in which some pairs of processes are sequential and some are concurrent (i.e., the processes are partially ordered). We propose a natural definition of a stage for such sets of processes. For partially ordered processes, with our definition of a stage, if two experimental factors selectively influence two different processes by increments, each within a different stage, then the factors have additive effects. If each process selectively influenced by increments is in the same stage, then an interaction is possible, although not inevitable.     

Selective Influence and Response Time Cumulative Distribution Functions in Serial-Parallel Task Networks

We analyze sets of mental processes, some of which are concurrent and some of which are sequential, under the assumption that the processes are partially ordered, that is, arranged in a directed acyclic network. Information about the process arrangement can be discovered by examining the effects on response time of selectively influencing process durations. Previous work has mainly focused on analyses of mean response times. Here we consider analyses based on cumulative distribution functions, for one of the major classes of directed acyclic networks, serial-parallel networks. When two processes are selectively influenced, patterns in the cumulative distribution functions can be used to test whether the processes are sequential or concurrent and whether the task network has AND gates or OR gates. Cumulative distribution functions are potentially more informative than means, and some previous results for means are shown to follow from our results for cumulative distribution functions. Copyright 2000 Academic Press.     

The phonological similarity effect in immediate recall: Positions of shared phonemes

Earlier literature proposes two ways phonological similarity could harm immediate recall: (1) It could increase the degradation of the representations of items in memory, or (2) it could decrease the probability that a degraded representation is correctly reconstructed. A multinomial processing tree model for each hypothesis was used to analyze an immediate recall experiment. Both gave a good account of the data, but, of the two, results favor the hypothesis that the effect of phonological similarity is to impair reconstruction of degraded representations. A second issue is whether positions of repeated phonemes in phonologically similar items matter. We found that mere repetition of phonemes produced a phonological similarity effect. Repeated phonemes in the same positions appeared to produce a greater effect. A final finding is that when reading rate was preequated, phonological similarity affected memory span by changing the time taken to recall a list of span length.     

Task switching and response correspondence in the psychological refractory period paradigm

Three experiments examined the effects of task switching and response correspondence in a psychological refractory period paradigm. A letter task (vowel-consonant) and a digit task (odd-even) were combined to form 4 possible dual-task pairs in each trial: letter-letter, letter-digit, digit-digit, and digit-letter. Foreknowledge of task transition (repeat or switch) and task identity (letter or digit) was varied across experiments: no foreknowledge in Experiment 1, partial foreknowledge (task transition only) in Experiment 2, and full foreknowledge in Experiment 3. For all experiments, the switch cost for Task 2 was additive with stimulus onset asynchrony, and the response-correspondence effect for Task 2 was numerically smaller in the switch condition than in the repeat condition. These outcomes suggest that reconfiguration for Task 2 takes place after the central processing of Task 1 and that the crosstalk correspondence effect is due to response activation by way of stimulus-response associations.