John Cerella

The rise and fall in information-processing rates over the life span

We surveyed studies that measured information-processing durations in groups of experimental subjects (children or elderly adults) and a group of college-aged control subjects. Some studies varied the type of processing while keeping the age of a subject group fixed. Process-durations in experimental subjects could be described by a multiplicative function of the control durations, regardless of the type of processing. Other studies varied the age of the subject groups while keeping the type of processing fixed. Process-durations declined during childhood, in a manner that could be described by a negative exponential function of age. Process-durations increased throughout middle- and old-age, in a manner that could be described by a positive exponential function of age. The sum of the two exponentials defined a U-shaped function that described process-durations over the life span. The most important studies varied both the type of processing and the age of the subject groups. An array of measurements of this kind could be described by a two-dimensional function that combined the multiplicative effect of process-duration and the exponential effects of age. The multiplicative effect of process-duration suggested that the execution of a processing sequence was conditioned by a single developmental parameter in both the experimental subject and the control subject. The exponential components determined the magnitude of the developmental parameter as the age of the subject changed. Given the global character of these effects, it seemed to us that the developmental mechanism may operate at a more elementary level than the information-processing stages conceived by cognitive theories. In a developmental framework, information processing may be reducible to a large number of small steps of a homogeneous duration or reliability, such as might be realized on a neural network. The exponential rate constants may be related to constant-probability hazards that act on one or another population of neural elements to create minute defects or incremental improvements. Their cumulative effects alter the functioning of the network over its lifetime, in a way that parallels the observed changes in process-durations.

Pigeons and perceptrons

Abstract The laboratory pigeon is able to classify images into natural categories such as people, trees, fish, etc. A series of experiments suggested that the pigeon does so by cueing on specific features. There was no tolerance of noise or of perspective distortion, and no recovery of the three-dimensional target. It appeared that the pigeons capacity could be described by a diameter-limited perceptron. A second series of experiments revealed that feature detection was, in fact, translation invariant: responding extended to any permutation of the feature set. Thus, the pigeon can be more accurately described as extracting the first order invariants from an image class. This first order limitation may be tied to the near-field grain acquisition system, and may not apply to the far-field flight control system.

Pigeon pattern perception: limits on perspective invariance.

Two experiments are reported in which the response of pigeons to perspective transformations of a pattern target was measured. In the first experiment an alphabet letter was taken as the pattern target (the ‘positive’) and the response to its perspective transforms was compared to the response to nontarget letters (‘negatives’) over the course of discrimination training. In the second experiment irregular quadrilaterals were used as positives and the responses to slight perspective deformations of the prototypes were compared to the responses to random transformations of the same magnitude under steady-state conditions. The amount of differential responding depended on the type of transformation. There was no differential response to targets rotated in the picture plane or around the horizontal axis in either experiment. There was differential response to small reductions and enlargements of the target. There was also differential response to translated targets, and this was seen irrespective of the amount of displacement. Results from targets rotated around the vertical axis were erratic, some target-plus-angle combinations elicited differential responding, but most did not. The erratic responses are attributed to symmetries in pattern elements that were abstracted as critical features. Pigeons therefore exhibit no true rotation invariance, limited size invariance, and complete shift invariance. It is argued that size invariance, but not position invariance, may depend on prior exposure to the alternatives.

Relations between information processing and intelligence in elderly adults

Abstract Measures of verbal intelligence and abstract reasoning were taken on a group of 31 college-aged and 32 elderly adults, together with mental-processing rates associated with choice reaction time, primary memory scanning, and lexical decoding. Group means showed that both verbal IQ and lexical decoding were intact in the elderly subjects, a relationship in keeping with theorizing of Hunt (1978). In contrast, there were large declines in both Ravens scores and a variety of CRT measures, in keeping with theorizing of Jensen (1980). The group results were upheld at the level of individual subjects in the verbal domain, but in the case of CRT, only intercept values, not slopes, correlated with abstract reasoning. Memory-scanning rates were unrelated to intelligence measures.

Age differences in depicting and perceiving tridimensionality in simple line drawings

Twelve young adults (M = 21 years) and twelve elderly adults (M = 67 years) were asked to draw a solid cube. The depictions produced by elderly adults were rated by judges as less accurate than the depictions produced by young adults. Both age groups were also asked to evaluate cube drawings that were deliberately distorted in ways characteristic of the depictions produced by older adults. Compared to younger participants, the elderly were more likely to accept distorted drawings as accurate. Control tasks demonstrated that older adults were able to draw and evaluate simpler two-dimensional patterns on par with younger adults. Apparently the mental representation of tridimensional information deteriorates with age leading to deficits in both production and recognition.

THE EFFECTS OF SEMANTIC PROCESSING ON MEMORY OF SUBJECTS DIFFERING IN AGE

This study contrasted the recall and recognition performance of young (19‐year‐old) and old (74‐year‐old) adults following intentional and incidental learning. The incidental learning condition involved the reading of a story. The large age deficit found in intentional recall was virtually eliminated in incidental recognition. Reading evidently induces a sufficient depth of processing to overcome memory loss.