The “magical” number 7 (±2)

“First, the span of absolute judgment and the span of immediate memory impose severe limitations on the amount of information that we are able to receive, process, and remember. by organizing the stimulus input simultaneously into several dimensions and successively into a sequence or chunks, we manage to break (or at least stretch) this informational bottleneck. second, the process of recoding is a very important one in human psychology and deserves much more explicit attention than it has received. in particular, the kind of linguistic recoding that people do seems to me to be the very lifeblood of the thought processes. recoding procedures are a constant concern to clinicians, social psychologists, linguists, and anthropologists and yet, probably because recoding is less accessible to experimental manipulation than nonsense syllables or t mazes, the traditional experimental psychologist has contributed little or nothing to their analysis. nevertheless, experimental techniques can be used, methods of recoding can be specified, behavioral indicants can be found. and i anticipate that we will find a very orderly set of relations describing what now seems an uncharted wilderness of individual differences. third, the concepts and measures provided by the theory of information provide a quantitative way of getting at some of these questions. the theory provides us with a yardstick for calibrating our stimulus materials and for measuring the performance of our subjects. in the interests of communication i have suppressed the technical details of information measurement and have tried to express the ideas in more familiar terms; i hope this paraphrase will not lead you to think they are not useful in research. informational concepts have already proved valuable in the study of discrimination and of language; they promise a great deal in the study of learning and memory; and it has even been proposed that they can be useful in the study of concept formation. a lot of questions that seemed fruitless twenty or thirty years ago may now be worth another look. in fact, i feel that my story here must stop just as it begins to get really interesting. and finally, what about the magical number seven? what about the seven wonders of the world, the seven seas, the seven deadly sins, the seven daughters of atlas in the pleiades, the seven ages of man, the seven levels of hell, the seven primary colors, the seven notes of the musical scale, and the seven days of the week?…”

“Despite the impressive complexity and processing power of the human brain, it is severely capacity limited. behavioral research has highlighted three major bottlenecks of information processing that can cripple our ability to consciously perceive, hold in mind, and act upon the visual world, illustrated by the attentional blink (ab), visual short-term memory (vstm), and psychological refractory period (prp) phenomena, respectively. a review of the neurobiological literature suggests that the capacity limit of vstm storage is primarily localized to the posterior parietal and occipital cortex, whereas the ab and prp are associated with partly overlapping fronto-parietal networks. the convergence of these two networks in the lateral frontal cortex points to this brain region as a putative neural locus of a common processing bottleneck for perception and action. © 2005 elsevier ltd. all rights reserved.”

“Visual categorization appears both effortless and virtually instantaneous. the study by thorpe et al. (1996) was the first to estimate the processing time necessary to perform fast visual categorization of animals in briefly flashed (20 ms) natural photographs. they observed a large differential eeg activity between target and distracter correct trials that developed from 150 ms after stimulus onset, a value that was later shown to be even shorter in monkeys! with such strong processing time constraints, it was difficult to escape the conclusion that rapid visual categorization was relying on massively parallel, essentially feed-forward processing of visual information. since 1996, we have conducted a large number of studies to determine the characteristics and limits of fast visual categorization. the present chapter will review some of the main results obtained. i will argue that rapid object categorizations in natural scenes can be done without focused attention and are most likely based on coarse and unconscious visual representations activated with the first available (magnocellular) visual information. fast visual processing proved efficient for the categorization of large superordinate object or scene categories, but shows its limits when more detailed basic representations are required. the representations for basic objects (dogs, cars) or scenes (mountain or sea landscapes) need additional processing time to be activated. this finding is at odds with the widely accepted idea that such basic representations are at the entry level of the system. interestingly, focused attention is still not required to perform these time consuming basic categorizations. finally we will show that object and context processing can interact very early in an ascending wave of visual information processing. we will discuss how such data could result from our experience with a highly structured and predictable surrounding world that shaped neuronal visual selectivity.”

“Capacity limits are a hallmark of visual cognition. the upper boundary of our ability to individuate and remember objects is well known but-despite its central role in visual information processing-not well understood. here, we investigated the role of temporal limits in the perceptual processes of forming ‘object files.’ specifically, we examined the two fundamental mechanisms of object file formation-individuation and identification-by selectively interfering with visual processing by using forward and backward masking with variable stimulus onset asynchronies. while target detection was almost unaffected by these two types of masking, they showed distinct effects on the two different stages of object formation. forward ‘integration’ masking selectively impaired object individuation, whereas backward ‘interruption’ masking only affected identification and the consolidation of information into visual working memory. we therefore conclude that the inherent temporal dynamics of visual information processing are an essential component in creating the capacity limits in object individuation and visual working memory. (psycinfo database record (c) 2013 apa, all rights reserved) (journal abstract)”