Tactile rod bisection in the absence of visuo-spatial processing in children, mid-age and older adults.

The effect of age on tactile rod bisection is explored in an attempt to fully understand lateralized biases that are not driven by prior experience or visual processing. In Experiment 1, a total of 549 healthy participants aged between 3 and 84 years of age, divided into eight age groups, used touch alone without vision to bisect one wooden rod. Participants across all age groups, except those approaching or in adolescence, showed pseudoneglect on tactile rod bisection. In Experiment 2 a total of 72 healthy participants aged between 6 and 96 years old, divided into three age groups, used touch alone without vision to bisect three wooden rods of different length. Experiment 2 showed pseudoneglect across the full adult life span and most notably in the oldest participants. For the youngest participants there was not a significant pseudoneglect bias but there was a significant effect of gender with females showing greater leftward bias than males. When participants scanned and bisected the rods starting from the right-hand side, pseudoneglect was significantly enhanced; again this bias interacted with age. The results suggest that the right hemisphere exerts an early capacity to orient attention contralaterally and that this capacity continues in middle and older adulthood which is inconsistent with current models of cognitive ageing. The findings are discussed in terms of how the right hemisphere preferentially orients attention leftward in the absence of direct visuo-spatial processing across lifespan and how this may be modulated by variables like gender and starting position.