The effect of manipulating image decomposability on mental rotation performance in older and younger adults. Paula Engelbrecht & Itiel Dror

Introduction A variety of cognitive functions have been found to decline with age:  Memory (e.g. Park et al., 1996)  Reasoning (e.g. Gilinsky & Jud, 1994)  Spatial-visualisation ability (e.g. Salthouse et al., 1990) Underlying assumption: Younger and older adults use the same processing mechanisms.

Introduction Does this assumption hold true?  Neuroimaging study: No age-related difference in memory for visual scenes. Age-related prefrontal overactivation and underactivation in the medial temporal lobe (Gutchess et al., 2005).  Strategic processes can compensate for age- related functional decline. Qualitative age-related differences in the way in which information is processed.

Introduction Qualitative age-related differences have also been found in mental imagery.  Mental rotation paradigm (Dror et al., 2005): Younger adults employ a piecemeal strategy. Older adults employ a holistic strategy. Aim: To investigate the boundary conditions of these age-related differences.  Are they fixed and inflexible?

Introduction Image decomposability was manipulated through the use of colour.  High decomposability: Image segments were highlighted with colour.  Low decomposability: line-drawings. Rationale: High decomposability manipulation facilitates piecemeal processing.

Predictions Differences in rotation slope reflect qualitative differences in the underlying mental rotation process (e.g. Folk & Luce, 1987; Dror et al., 2007). If image decomposability affects mental rotation then this should be reflected in differing rotation slopes for high and low decomposability images. Otherwise rotated at the same rate.

Method Participants  20 older adults (12 females) with a mean age of 76 years (SD = 5.2 years).  20 younger adults (15 females) with a mean age of 26 years (SD = 3.4 years).

Method

Results Response time data was analysed separately for younger and older adults using ANOVAs. Stimulus decomposability (high and low) and angle of rotation (0, 35, 70 and 105 degrees) were the two within subjects variables.

Results

The younger adults responded faster to high decomp. (M = ms, SE = ms) than to low decomp. (M = ms, SE = ms) stimuli. No significant difference for the older adults. Main effect reflects initial encoding not mental rotation performance.

Results

Discussion Younger adults:  Differences in rotation slopes for high and low decomposability images suggests that these are processed differently.  Previous research associates shallow rotation slopes with holistic processing and steep rotation slopes with piecemeal processing.

Discussion Older adults:  Rotation performance did not vary as a function of stimulus decomposability.  Suggests that they employed the same processing strategy to rotate both high and low decomposability stimuli.  A previous study found that older adults prefer a holistic processing strategy (Dror et al., 2005).  Holistic processing is less resource intensive (Logan, 1988).

Conclusions Findings suggest that older adults favour a holistic processing style regardless of image decomposability. Their processing strategies appear to be less affected by environmental manipulations. Investigating qualitative changes deepens our understanding of the aging mind.

Results AngleOverallYounger AdultOlder Adults % (SE = 1.5%) 21.89% (SE = 2.1%) 20.5% (SE = 2.12%) % (SE = 1.6%) 23.3% (SE= 2.3%) 21.3% (SE = 2.3%) % (SE = 1.6%) 27% (SE = 2.2%) 22.8% (SE = 2.2%) % (SE = 1.9%) 26% (SE = 2.6%) 23.4% (SE = 2.6%)