The cost of serially chaining two cognitive operations

As Turing (1936, Proceedings of the London Mathematical Society) noted, a fundamental process in human cognition is to effect chained sequential operations in which the second operation requires an input from the preceding one. Although a great deal is known about the costs associated with 'independent' (unrelated) operations, e.g., from the classic psychological refractory period paradigm, far less is known about those operations to which Turing referred. We present the results of two behavioural experiments, where participants were required to perform two speeded sequential tasks that were either chained or independent. Both experiments reveal the reaction time cost of chaining, over and above classical dual-task serial costs. Moreover, the chaining operation significantly altered the distribution of reaction times relative to the Independent condition in terms of an increased mean and variance. These results are discussed in terms of the cognitive architecture underlying the serial chaining of cognitive operations.     

Phonological and motoric demands in handwriting: evidence for discrete transmission of information

In an experiment with handwriting tasks effects of phonological and motoric task factors upon reaction time and movement time were measured to test implications of a discrete information processing account of the task. The model is built up of serially organized stages, each of which monitors one specific type of operation, necessary to generate a message. The serial structure of the model is defined as the limitation that higher levels of the model provide their output to the next lower processor in the hierarchy, and receive their input from the next higher stage. The parallel character of the model is exemplified through the assumption that all processors are active at the same time and concurrently with the real time production of writing movements. The study adds evidence that a serial architecture of processors can be compatible with the parallel processing of a message as long as more abstract operations are prepared more in advance to real-time movements than operations lower in the hierarchy. In the experiment the prediction was tested that the time course of the manifestation of phonological and motoric task demands reflects the discrete and serial structure of the model.     

The simultaneous chain: a new approach to serial learning

Recent advances have allowed the application of behaviorism's rigor to the control of complex cognitive tasks in animals. This article examines recent research on serially organized behavior in animals. 'Chaining theory', the traditional approach to the study of such behavior, reduces intelligent action to sequences of discrete stimulus-response units in which each overt response is evoked by a particular stimulus. However, such theories are too weak to explain many forms of serially organized cognition, both in humans and animals. By training non-human primates to produce arbitrary sequences that cannot be learned as chains of particular motor responses, the simultaneous chaining paradigm has overcome limitations of chaining theory in experiments on serial expertise, the use of numerical rules, knowledge of ordinal position, and distance and magnitude effects.     

Parallel versus serial processing and individual differences in high-speed search in human memory

Many mental tasks that involve operations on a number of items take place within a few hundred milliseconds. In such tasks, whether the items are processed simultaneously (in parallel) or sequentially (serially) has long been of interest to psychologists. Although certain types of parallel and serial models have been ruled out, it has proven extremely difficult to entirely separate reasonable serial and limited-capacity parallel models on the basis of typical data. Recent advances in theory-driven methodology now permit strong tests of serial versus parallel processing in such tasks, in ways that bypass the capacity issue and that are distribution and parameter free. We employ new methodologies to assess serial versus parallel processing and find strong evidence for pure serial or pure parallel processing, with some striking apparent differences across individuals and interstimulus conditions.     

Increased control demand results in serial processing: evidence from dual-task performance

Increased demands on cognitive control trigger changes in processing mode. One such modulation involves a shift from parallel to serial processing. This study assessed the role of control demand in determining whether dual-task processing is performed serially or in parallel. We used two critical indices, based on the response-selection bottleneck model, to show that response selection was serial when a task switch was involved, but partly parallel when the simultaneous performance of the tasks did not involve task switching.     

The effect of the position of atypical character-to-sound correspondences on reading kanji words aloud: Evidence for a sublexical serially operating kanji reading process

In English, the size of the regularity effect on word reading-aloud latency decreases across position of irregularity. This has been explained by a sublexical serially operating reading mechanism. It is unclear whether sublexical serial processing occurs in reading two-character kanji words aloud. To investigate this issue, we studied how the position of atypical character-to-sound correspondences influenced reading performance. When participants read inconsistent-atypical words aloud mixed randomly with nonwords, reading latencies of words with an inconsistent-atypical correspondence in the initial position were significantly longer than words with an inconsistent-atypical correspondence in the second position. The significant difference of reading latencies for inconsistent-atypical words disappeared when inconsistent-atypical words were presented without nonwords. Moreover, reading latencies for words with an inconsistent-atypical correspondence in the first position were shorter than for words with a typical correspondence in the first position. This typicality effect was absent when the atypicality was in the second position. These position-of-atypicality effects suggest that sublexical processing of kanji occurs serially and that the phonology of two-character kanji words is generated from both a lexical parallel process and a sublexical serial process.     

Nonconscious perception, conscious awareness and attention

Because it is unclear how a nonconscious stimulus is cognitively processed, there is uncertainty concerning variables that modulate the processing. In this context recent findings of a set of neuroimaging experiments are important. These findings suggest that conscious and nonconscious stimuli activate same areas of the brain during performance of a similar task. Further, different areas are activated when a task is performed with or without awareness of processing. It appears that the neural network involved in cognitive processing depends on the awareness of processing rather than awareness of perception. Since conscious and nonconscious cognitive processing use separate neural networks, each processing is modulated by different variables. Attention modulates most conscious cognitive processing and most, but not all, nonconscious processing is attention dependent. Nonconscious tasks that require attentional resources, with or without conscious awareness, are processed using the attention dependent system. Further, because attention dependent and attention independent tasks are processed by separate neural networks, the cognitive processing and modulating variables can be understood better if cognitive tasks are defined as attention dependent or attention independent, rather than conscious or nonconscious.     

Repetition blindness is immune to the central bottleneck

Theattentional blink (AB) andrepetition blindness (RB) phenomena refer to subjects’ impaired ability to detect the second of two different (AB) or identical (RB) target stimuli in a rapid serial visual presentation stream if they appear within 500 msec of one another. Despite the fact that the AB reveals a failure of conscious visual perception, it is at least partly due to limitations at central stages of information processing. Do all attentional limits to conscious perception have their locus at this central bottleneck? To address this question, here we investigated whether RB is affected by online response selection, a cognitive operation that requires central processing. The results indicate that, unlike the AB, RB does not result from central resource limitations. Evidently, temporal attentional limits to conscious perception can occur at multiple stages of information processing.     

How serial is serial processing in vision?

Visual search for an element defined by the conjunction of its colour and orientation has previously been shown to be a serial processing task since reaction times increase linearly with the number of distractor elements used in the display. Evidence is presented that there are parallel processing constituents to this serial search. Processing time depended on the ratio of the number of the two distractor types used, suggesting that only one type was scanned. Which type was scanned also depended on the distractor ratio, indicating that this decision was made after stimulus presentation and was based on a parallel figure-ground separation of the stimulus elements. Furthermore, in accordance with this serial scanning model, there was an increase in processing speed (elements scanned per second) with increase in number of elements to be scanned. This increased efficiency suggests that clumps of elements were processed synchronously. Under the stimulation conditions used, clumps contained six to sixteen elements and each clump was processed in 50-150 ms.     

Somatosensory processes subserving perception and action

The functions of the somatosensory system are multiple. We use tactile input to localize and experience the various qualities of touch, and proprioceptive information to determine the position of different parts of the body with respect to each other, which provides fundamental information for action. Further, tactile exploration of the characteristics of external objects can result in conscious perceptual experience and stimulus or object recognition. Neuroanatomical studies suggest parallel processing as well as serial processing within the cerebral somatosensory system that reflect these separate functions, with one processing stream terminating in the posterior parietal cortex (PPC), and the other terminating in the insula. We suggest that, analogously to the organisation of the visual system, somatosensory processing for the guidance of action can be dissociated from the processing that leads to perception and memory. In addition, we find a second division between tactile information processing about external targets in service of object recognition and tactile information processing related to the body itself. We suggest the posterior parietal cortex subserves both perception and action, whereas the insula principally subserves perceptual recognition and learning.     

Hemispheric differences in processing visual patterns

The dichotomies verbal/visuospatial, serial/parallel and analytic/holistic are reviewed with respect to differences in hemispheric processing. A number of experimental parameters may be varied in such tasks, and together with certain frequently-occurring weaknesses of experimental design may account for the often discrepant results hitherto reported. The above factors are systematically reviewed, and three further experiments are reported which attempt to fill in the missing designs. Further evidence is given in support of the hypothesis that right-hemisphere superiority is most apparent in processes leading to identity matching. It is quantitative rather than qualitative, and may depend upon operations on the entire gestalt, such as holistic matching, mental rotation, reflection, distortion, etc., rather than, e.g., simultaneous (parallel) processing of discretely analysed or isolated features or elements. On the other hand left-hemisphere involvement in visuospatial processing is thought to reflect analysis of the configuration into its separable components; such processing may be either serial or parallel, and may frequently lead to a judgement different.     

Development of parafoveal processing within and across words in reading: Evidence from the boundary paradigm

In this study we used the boundary paradigm to examine whether readers extract more parafoveal information within than across words. More specifically, we examined whether readers extract more parafoveal information from a compound word's second constituent than from the same word when it is the noun in an adjective–noun phrase (kummitustarina “ghost story” vs. lennokas tarina “vivid story”). We also examined whether the processing of compound word constituents is serial or parallel and how parafoveal word processing develops over the elementary school years. Participants were Finnish adults and 8-year-old second-, 10-year-old fourth-, and 12-year-old sixth-graders. The results showed that for all age groups more parafoveal information is extracted from the second constituent within compounds than from the noun in adjective–noun phrases. Moreover, for all age groups we found evidence for parallel processing of constituents within compounds, but only when the compounds were of high frequency. In sum, the present study shows that attentional allocation extends further to the right and is more simultaneous when words are linguistically and spatially unified, providing evidence that attention in text processing is flexible in nature.     

COGNITIVE SUPPRESSION DURING SACCADIC EYE MOVEMENTS

Abstract— Saccadic eye movements are made at least 100,000 times each day It is well known that sensitivity to visual input is suppressed during saccades, we examined whether cognitive activity (specifically, menial rotation) is suppressed as well If cognitive processing occurs during saccades, a prime viewed in one fixation should exert a larger influence on a target viewed in a second fixation when a long rather than a short saccade separates their viewing No such effect was found, even though the lime difference between long and short saccades was effective in a no-saccade control These results indicate that at least some cognitive operations are suppressed during saccades     

双任务情境下心理旋转的并行加工机制

采用心理不应期研究范式,三个反应时实验检测了心理旋转任务和其他认知操作任务能否并行加工的问题。在每个实验中要求被试快速、系列地完成对高低音的辨别任务(T1)和不同旋转角度的正反像辨别任务(T2),T1和T2呈现的时间间隔运用变化的SOA。结果发现：(1)T1的反应选择对T2的反应选择产生了很大的影响,在T2上PRP效应显著。心理旋转的操作成绩随着SOA的缩短而降低。(2)在T1上同样存在随着SOA缩短,反应时增加,正确率下降的趋势。T2的反应选择对T1的反应选择同样产生了显著的影响。(3)T2的反应选择对T1的中枢加工产生了相应的影响,表明当T1的反应选择占据中枢瓶颈时,心理旋转任务和其他认知操作任务在中枢瓶颈中并行得到了有效的加工     

Forced serial processing of words and letter strings: A reexamination

Words and nonword strings, three and seven letters long, were displayed serially (i.e., one letter at a time) or simultaneously, with or without a backward mask following display of each letter or string. Recognition of words, and of individual letters within words, was markedly impaired in the masked serial condition relative to the unmasked serial, unmasked simultaneous, and masked simultaneous conditions. Analogous differences were smaller or nonexistent for seven-letter nonwords; however, three-letter nonwords produced relatively “wordlike” data. Implications for the issue of spatially serial vs. parallel processing in word recognition are discussed.     

The structure of short-term memory scanning: an investigation using response time distribution models

A classic question in cognitive psychology concerns the nature of memory search in short-term recognition. Despite its long history of investigation, however, there is still no consensus on whether memory search takes place serially or in parallel or is based on global access. In the present investigation, we formalize a variety of models designed to account for detailed response time distribution data in the classic Sternberg (Science 153: 652-654, 1966) memory-scanning task. The models vary in their mental architectures (serial exhaustive, parallel self-terminating, and global access). Furthermore, the component processes within the architectures that make match/mismatch decisions are formalized as linear ballistic accumulators (LBAs). In fast presentation rate conditions, the parallel and global access models provide far better accounts of the data than does the serial model. LBA drift rates are found to depend almost solely on the lag between study items and test probes, whereas response thresholds change with memory set size. Under slow presentation rate conditions, even simple versions of the serial-exhaustive model provide accounts of the data that are as good as those of the parallel and global access models. We provide alternative interpretations of the results in our General Discussion.     

Elemental operations in vision

Many cognitive tasks are serial in that they require several steps that have to be carried out in a sequence. Here, I outline a new theory of how these processing steps are implemented in vision by networks of neurons that span several areas of the cerebral cortex. The theory explains how individual neurons can contribute to the elementary processing steps, and also how several processing steps can be arranged in a sequence to form more complex visual routines, just as computer programs can be composed of sequences of instructions. Evidence in support of the theory comes from recent neurophysiological findings in monkeys engaged in complex visual tasks. It is likely that future work will allow these ideas to be generalized to other sensory modalities and cognitive functions.     

Applying global workspace theory to the frame problem

The subject of this article is the frame problem, as conceived by certain cognitive scientists and philosophers of mind, notably Fodor for whom it stands as a fundamental obstacle to progress in cognitive science. The challenge is to explain the capacity of so-called informationally unencapsulated cognitive processes to deal effectively with information from potentially any cognitive domain without the burden of having to explicitly sift the relevant from the irrelevant. The paper advocates a global workspace architecture, with its ability to manage massively parallel resources in the context of a serial thread of computation, as an answer to this challenge. Analogical reasoning is given particular attention, since it exemplifies informational unencapsulation in its most extreme form. Because global workspace theory also purports to account for the distinction between conscious and unconscious information processing, the paper advances the tentative conclusion that consciousness may go hand-in-hand with a solution to the frame problem in the biological brain.     

Obsessive-compulsive tendencies are associated with a focused information processing strategy

The study examined the hypothesis that obsessive–compulsive (OC) tendencies are related to a reliance on focused and serial rather than a parallel, speed-oriented information processing style. Ten students with high OC tendencies and 10 students with low OC tendencies performed the flanker task, in which they were required to quickly classify a briefly presented target letter (S or H) that was flanked by compatible (e.g., SSSSS) or incompatible (e.g., HHSHH) noise letters. Participants received 4 blocks of 100 trials each, two with 50% compatible trials and two with 80% compatible trials and were informed of the probability of compatible trials before the beginning of each block. As predicted, high OC participants, as compared to low OC participants, had slower overall reaction time (RT) and lower tendency for parallel processing (defined as incompatible trials RT minus compatible trials RT). Low, more than high OC participants tended to adjust their focused/parallel processing including a shift towards parallel processing in blocks with 80% compatible trials and in trials following compatible trials. Implications of these results to the cognitive theory and therapy of OCD are discussed.