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This article outlines a research strategy for investigating, in a laboratory setting, the acquisition and the "limits" of a cognitive skill. Expert digit memory is used as an illustration. Two participants with initial average digit- and word-span memory were trained to memorize and reproduce strings of 80 to 90 digits presented at 10- to 1-sec rates. The instruction and training program, based on a theory of skilled memory, focused on three components: (a) acquisition of a mnemonic system (i.e., recoding digits into historical dates or concrete nouns), (b) use of a long-term memory retrieval structure (i.e., instruction in the Method of Loci), and (c) improvement in processing speed. After 86 experimental sessions, one participant recalled 90 random digits presented at a 1-sec rate. The digits were, however, constrained to be compatible with the participant's historical knowledge. The second participant recalled 80 random digits presented at a 5-sec rate after 70 sessions. Speed of encoding and retrieval processing was the only component that required extensive practice for skilled digit-memory acquisition.
The optical density of human macular pigment was measured for 50 observers ranging in age from 10 to 90 years. The psychophysical method required adjusting the radiance of a 1°, monochromatic light (400–550 nm) to minimize flicker (15 Hz) when presented in counterphase with a 460 nm standard. This test stimulus was presented superimposed on a broad-band, short-wave background. Macular pigment density was determined by comparing sensitivity under these conditions for the fovea, where macular pigment is maximal, and 5° temporally. This difference spectrum, measured for 12 observers, matched Wyszecki and Stiles's standard density spectrum for macular pigment. To study variation in macular pigment density for a larger group of observers, measurements were made at only selected spectral points (460, 500 and 550 nm). The mean optical density at 460 nm for the complete sample of 50 subjects was 0.39. Substantial individual differences in density were found (ca. 0.10–0.80), but this variation was not systematically related to age.
On the locus of training gains in research on the plasticity of fluid intelligence in old age
(1988)
Cognitive training research has shown that many older adults have a substantial reserve capacity in fluid intelligence. Little is known, however, about the locus of plasticity. Two studies were conducted to examine whether training gains in fluid abilities are critically dependent on experimenter-guided training and/or whether older adults can achieve similar improvements by themselves on the basis of cognitive skills already available in their repertoire. Several comparisons were made: (a) between test performances after trainer-guided training in ability-specific cognitive skills and after self-guided retest practice (without feedback), (b) between performances under speeded and power conditions of assessment, (c) between performances on easy and difficult items, and (d) between the relative numbers of correct and wrong answers. Results suggest that a large share of the training improvement shown by the elderly can plausibly be explained as the result of the activation and practice of cognitive skills already available in their repertoire. The results also have implications for educational practice, pointing to the appropriateness of strategies of self-directed learning for many elderly adults.
Gedächtnishöchstleistungen sind auch im Alter möglich. Dies konnte am Beispiel der »Methode der Orte« experimentell bestätigt werden. Hierbei hat sich gezeigt, daß das Gehirn über große kognitive Kapazitätsreserven verfügt. In einer speziellen Testmethode (»testing the limits«) zeigt sich aber im Hochleistungsbereich, trotz der grundsätzlichen Plastizität, ein altersbezogenes Nachlassen der Gedächtnismechanik. Offenbar gibt es biologische Grenzen in der Schnelligkeit der menschlichen Vorstellungskraft. Vielleicht gelingt es auf der Grundlage dieser Erkentnnis, einen zuverlässigen Markierungsindikator für das hirnphysiologische Altern zu finden. Daraus könnten sich auch neue Methoden zur Früherkennung von Demenzen ableiten lassen.
Cognitive research on the plasticity of fluid intelligence has demonstrated that older adults benefit markedly from guided practice in cognitive skills and problem-solving strategies. We examined to what degree older adults are capable by themselves of achieving similar practice gains, focusing on the fluid ability of figural relations. A sample of 72 healthy older adults was assigned randomly to three conditions: control, tutor-guided training, self-guided training. Training time and training materials were held constant for the two training conditions. Posttraining performances were analyzed using a transfer of training paradigm in terms of three indicators: correct responses, accuracy, and level of item difficulty. The training programs were effective and produced a significant but narrow band of within-ability transfer. However, there was no difference between the two training groups. Older adults were shown to be capable of producing gains by themselves that were comparable to those obtained following tutor-guided training in the nature of test-relevant cognitive skills.
Investigated the range and limits of cognitive reserve capacity as a general approach to the understanding of age differences in cognitive functioning. Testing-the-limits is proposed as a research strategy, Data are reported from 2 training studies involving old (65 to 83 years old) and young adults (19 to 29 years old). The training, designed to engineer an expertise in serial word recall, involved instruction and practice in the Method of Loci. Substantial plasticity was evident in pretest to posttest comparisons. Participants raised their serial word recall several times above that of pretest baseline. Age-differential limits in reserve capacity were evident in amount of training gain but not in responses to conditions of increased test difficulty (speeded stimulus presentation). Group differences were magnified by the training to such a degree that age distributions barely overlapped at posttests. Testing-the-limits offers promise in terms of understanding the extent and nature of cognitive plasticity.
Kognitive Plastizität und altersbedingte Grenzen am Beispiel des Erwerbs einer Gedächtnistechnik
(1989)
Die Bedeutung kognitiver Entwicklungskapazität (Plastizität) und ihrer altersabhängigen Grenzen für Theorien kognitiven Alters wird thematisiert. Für kognitive Basisprozesse wird erwartet, daß die durch Training umgesetzte Entwicklungskapazität älterer Menschen zwar ausreicht, die Ausgangsleistung junger Erwachsener zu übertreffen, daß aber aufgrund altersbedingter Grenzen der Entwicklungskapazität nur sehr wenige ältere Erwachsene das Leistungsniveau trainierter junger Erwachsener erreichen werden. Am Beispiel eines Gedächtnistrainingsprogrammes zur Erhöhung der Merkfähigkeit für Wortlisten werden zwei Forschungsstrategien vorgestellt: (a) das Training von sehr leistungsfähigen älteren Erwachsenen und (b) Längsschnitt-Einzelfall-Studien. Die experimentellen Befunde bestätigten die theoretischen Erwartungen. Zwar waren die Leistungen der besten älteren Erwachsenen etwa doppelt so hoch wie die untrainierter junger Erwachsener, aber die durch das Training aufgedeckten Altersverluste konnten auch in bis zu 75 weiteren Übungsstunden nicht behoben werden.
The focus of this study was on developmental reserve capacity in old age as revealed by testing-thelimits. We examined (a) the time course of training-related magnification of age differences in serial word recall and (b) predictability of training gains by pretest individual differences in cognitive abilities. In 20 sessions, young (n = 18) and old (n = 19) adults were taught to recall lists of 30 words using the Method of Loci. Age differences were magnified early in practice at long presentation times (20 s and 15 s per word) and later at 5 s per word. Regression of posttraining scores on various pretraining abilities revealed significant effects of digit symbol substitution. Also, consistent with the assumption of age-related decline in developmental reserve capacity, the unique variance in serial word recall associated with age group became more salient as the training unfolded.
We investigated the role of training-induced knowledge Schemas and encoding time on adult age differences in recall. High-plausible (schema coherent) words were recalled better than lowplausible (schema discrepant) words in both age groups. This difference was larger for old-adults than for young adults for presentation times ranging from 3 s to 11 s per word. After equating participants in overall recall (i.e., at 50% correct) by dynamic adjustment of presentation time, old adults again showed a stronger plausibility effect than young adults when recall was above criterion. In a second experiment with self-paced encoding, old adults used more time than young adults only for low-plausible pairs, yet they still remembered fewer of them. In a third experiment, both age groups preferred to imagine high- rather than low-plausible words, but this effect was more pronounced in old adults. The results indicate that, compared with young adults, old adults find it particularly difficult to form elaborative mental images of schema-discrepant information under a wide variety of time constraints during encoding. Results are discussed in relation to explanations based on age-related mental slowing.
Bisherige Ergebnisse der kognitiven Altersforschung erlauben keine Schlußfolgerung darüber, ob die Größe und Robustheit der Altersverluste in kognitiven Basisprozessen irreversibel sind und folglich als Indikatoren neurobiologischer Grenzen des alternden Organismus interpretiert werden können: Durch die Forschungsstrategie des Testing-the-Limits wurden im Zusammenhang mit einer kognitiven Intervention zuverlässige Ergebnisse bezüglich alterskorrelierter Grenzen kognitiver Entwicklungskapazität erwartet. Gesunde ältere und junge Erwachsene nahmen an 38 über ein Jahr verteilten experimentellen Sitzungen teil, in denen sie in einer Gedächtnistechnik, der Methode der Orte, trainiert und wiederholt getestest wurden. Die Kriteriumsaufgabe war das Behalten langer Wortlisten auf der Grundlage der Erzeugung phantasievoller Gedankenbilder. Obwohl ältere Erwachsene in der Lage waren, die Gedächtnistechnik zu erwerben, zeigte sich unter Testing-the-Limits- Bedingungen eine nahezu vollständige Entzerrung der Leistungsverteilungen junger und älterer Erwachsener, die auch durch langfristiges Training nicht abgebaut wurde. Die Ergebnisse werden in Hinblick auf (1) die Bedeutung spezifischer kognitiver Basisprozesse, (2) Kohorten- bvs. biologische Alterseffekte und (3) mögliche Ausnahmen vom Altersabbau diskutiert.
Elderly adults (N = 116; average age = 73 years) were randomly assigned to one of four treatment groups varying in the amount of training and testing on fluid intelligence tests. They were compared before and after treatment on self-efficacy and utility beliefs for intelligence tests and everyday competence. Although both ability training and extended retest practice resulted in significant gains in objective test performance (Baltes, Kliegl, & Dittmann-Kohli, 1988), only ability training resulted in positive changes in self-efficacy. However, these changes were restricted to testrelated self-efficacy. Training had no impact on perceived utility or on everyday self-efficacy beliefs. Implications of the results are discussed with regard to interventions to increase intellectual self-efficacy in elderly persons.
Earlier testing-the-limits research on age differences in cognitive plasticity of a memory skill was extended by 18 additional assessment and training sessions to explore whether older adults were able to catch up with additional practice and improved training conditions. The focus was on the method of loci, which requires mental imagination to encode and retrieve lists of words from memory in serial order. Of the original 37 subjects, 35 (16 young, ranging from 20 to 30 years of age, and 19 older adults, ranging from 66 to 80 years of age) participated in the follow-up study. Older adults showed sizable performance deficits when compared with young adults and tested for limits of reserve capacity. The negative age difference was substantial, resistant to extensive practice, and applied to all subjects studied. The primary origin for this negative age difference may be a loss in the production and use of mental imagination for operations of the mind.
Using a testing-the-limits paradigm, the authors investigated the modulation (attenuation) o f negative adult age differences in imagery-based memory performance as a function of professional expertise. Six older graphic designers, 6 normal older adults, 6 younger graphic design students, and 6 normal younger students participated in a 19-session program with a cued-recall variant of the Method of Loci. Older graphic designers attained higher levels o f mnemonic performance than normal older adults but were not able to reach younger adults' level of performance; a perfect separation of age groups was achieved. Spatial visualization was a good predictor of mnemonic performance. Results suggest that negative adult age differences in imagery-based memory are attenuated but not eliminated by the advantages associated with criterion-relevant ability (talent) and experience.
This paper presents a new methodology for examining the phenomenon of subitizing. Subjects were presented with a standard numerosity-detection task but for a range of presentation times to allow Task-Accuracy Functions to be computed for individual subjects. The data appear to show a continuous change in processing for numerosities from 2 to 5 when the data are aggregated across subjects. At the level of individual subjects, there appear to be qualitative shifts in enumeration processing after 3 or 4 objects. The approach used in this experiment may be used to test the claim that subitizing is a distinct enumeration process that can be used for small numbers of objects.
Sequential and coordinative complexity : age-based processing limitations in figural transformations
(1993)
Dimensions of cognitive complexity in figural transformations were examined in the context of adult age differences. Sequential complexity was manipulated through figural transformations of single objects in a multiple-object array. Coordinative complexity was induced through spatial or nonspatial transformations of the entire array. Results confirmed the prediction that age-related slowing is larger in coordinative complexity than in sequential complexity conditions. The effect was stable across 8 sessions (Experiment 1), was obtained when age groups were equated in accuracy with criterion-referenced testing (Experiment 2), and was corroborated by age-differential probabilities of error types (Experiments 1 and 2). A model is proposed attributing age effects under coordinative complexity to 2 factors: (a) basic-level slowing and (b) time-consuming reiterations through the processing sequence due to age-related working memory failures.
A model for correct recall and intrusions in cued recall of word lists is introduced. Intrusions are false responses that were correct in an earlier list. The model assumes 3 exclusive states for memory traces after encoding: with a list tag (i.e., with information about list origin), without list tags, and missing. Across lists, a trace can lose its list tag or its content. For retrieval, an optimal strategy of response selection was assumed. Younger and older laboratory-trained mnemonists participated in 2 experiments in which recall of permutations of a single word list across a single set of cues was held constant with individually adjusted presentation times. With correct recall equated to younger adults, older adults were more susceptible to intrusions. Age differences were restricted to model parameters estimating the probability of generation of list tags. Alternative accounts of age differences in context memory are discussed.
Past research suggests that age differences in measures of cognitive speed contribute to differences in intellectual functioning between young and old adults. To investigate whether speed also predicts age-related differences in intellectual performance beyond age 70 years, tests indicating 5 intellectual abilities—speed, reasoning, memory, knowledge, and fluency—were administered to a close-to-representative, age-stratified sample of old and very old adults. Age trends of all 5 abilities were well described by a negative linear function. The speed-mediated effect of age fully explained the relationship between age and both the common and the specific variance of the other 4 abilities. Results offer strong support for the speed hypothesis of old age cognitive decline but need to be qualified by further research on the reasons underlying age differences in measures of speed.
A paradigm for the determination of time-accuracy functions (TAFs) for individual participants is introduced for two pairs of tasks differing in cognitive complexity, that is, word scanning vs cued recognition and figural scanning vs figural reasoning. TAFs can be used to test dissociations of cognitive processes beyond scale-related ambiguities of ordinal interactions. The approach is applied to examine the cognitive-aging hypothesis that a single slowing factor can account for interactions between adult age and cognitive task complexity. Twenty young and 20 old adults participated in 17 sessions. Presentation times required for 75, 87.5, and 100% accuracies were determined for each task with a variant of the psychophysical method of limits. Accuracy was fit by negatively accelerated functions of presentation time. State-trace analyses showed that different slowing factors are required for high- and low-complexity tasks. Relations to speed-accuracy and performance-resource functions are discussed.