Michael Rönnlund

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Aspects of Declarative Memory Functioning in Adulthood

I BOKEN "ASPECTS of Declarative Memory Functioning in Adulthood" av Michael Rönnlund, undersöks deklarativ minnesfunktion hos vuxna genom både tvärsnittliga och longitudinella studier. Denna avhandling, som bygger på data från Betula Prospective Cohort Study, sträcker sig över en åldersgrupp från 35 till 90 år och syftar till att belysa hur minnesfunktioner förändras över tid.

Boken presenterar fyra centrala studier som analyserar episodiskt och semantiskt minne. I de första två studierna undersöks hur åldersrelaterade skillnader i episodiskt minne kan kompenseras genom olika former av inlärningsstöd, däribland en teknik som kallas enactment. Resultaten visar att denna metod fortsätter att vara effektiv för att stödja inlärning även hos äldre vuxna.

I den tredje studien jämförs olika modeller av deklarativt minne, där en tvåfaktormodell visade sig vara överlägsen en enhetsmodell. Den mest passande modellen identifierades som en sexfaktormodell, vilket ger insikter i hur episodiskt och semantiskt minne fungerar och utvecklas över tid. Den fjärde studien belyser skillnader mellan tvärsnittliga och longitudinella data, vilket visar att uppfattningar om minnesnedgång hos yngre vuxna kan vara missvisande.

Sammanfattningsvis bidrar "Aspects of Declarative Memory Functioning in Adulthood" med värdefull kunskap om hur deklarativt minne fungerar under vuxenlivet. Boken är av intresse för forskare och studenter inom kognitiv psykologi och relaterade områden, och erbjuder en djupgående analys av minnesprocesser samt deras förändringar med åldern. Genom att kombinera teoretiska perspektiv med empiriska resultat ger Rönnlund en grundlig förståelse för de faktorer som påverkar minnesfunktioner hos vuxna.

The general objective of the thesis was to examine aspects of declarative memory functioning across the adult life span. The four papers were based on data collected as part of the Betula Prospective Cohort Study (Nilsson et al., 1997) and included largescale population-based samples of participants in the age range 35 to 90. In study I and study II the possibility that age differences in episodic memory may be compensated for by provision of encoding support in the form of enactment was investigasted, using free and cued recall and recognition portioned into components of recollative experience as the dependent measures. In Study III, unitary, two-, and multi-factorial models of declarative memory were compared and age-invariance was tested for. In Study IV cross-sectional age differences were contrasted with five-year longitudinal changes on aggregate measures of episodic and semantic memory within age groups ranging from 35 to 85 years. The results of Study I and Study II demonstrated that enactment contitues an effective form of encoding support. Study II indicated that most of the age-related variance in recognition and levels of recollective experience following enacted and non-enacted encoding was shared by a measure of processing speed. Study III confirmed that a two-factor model of declarative memory (episodic and semantic memory) yields superior it as as compared with a unitary model of declarative memory. However, the best fitting model was a six-factor model with recall and recognition (episodic memory) and knowledge and fluency (semantic memory) as first-order factors. Episodic and semantic memory were found to be associated with different patterns of age-related differences, with some indications that the first-order factors show differential age-related patterns, indicative of variability within the episodic and semantic memory domains. The results of Study IV showed that cross-sectional data may give a false impression of decline for adults in the age range 35-60 years for episodic memory. There was no evidence of time-related decline withtin these age groups, even though practice effects were taken into account. However, past this age, substantial time-related decline was observed for the older adults, in line with cross-sectional data. Semantic memory performance tended to improve across time for the younger groups, but decline in old age, although the differences in education may be one important factor underlying the discrepancy episodic and semantic memory. In conclusion, the result of the present studies show episodic memory, but that the onset for decline does not begin until old age.