A Simple Target Interception Task as Test for Activities of Daily Life Performance in Older Adults

Abstract

Previous research showed that a simple target interception task reveals differences between younger adults (YA) and older adults (OA) on a large screen under laboratory conditions. Participants intercept downward moving objects while a horizontally moving background creates an illusion of the object moving in the opposite direction of the background. OA are more influenced by this illusory motion than YA. OA seem to be less able to ignore irrelevant sensory information than YA. Since sensory integration relates to the ability to perform Activities of Daily Living (ADL), this interception task can potentially signal ADL issues. Here we investigated whether the results of the target interception task could be replicated using a more portable setup, i.e., a tablet instead of a large touch screen. For YA from the same, homogeneous population, the main effects were replicated although the task was more difficult in the tablet set-up. After establishing the tablet's validity, we analyzed the response patterns of OA that were less fit than the OA in previous research. We identified three different illusion patterns: a (large) illusion effect (indicating over integration), a reverse illusion effect, and no illusion effect. These different patterns are much more nuanced than previously reported for fit OA who only show over integration. We propose that the patterns are caused by differences in the samples of OA (OA in the current sample were older and had lower ADL scores), possibly modulated by increased task difficulty in the tablet setup. We discuss the effects of illusory background motion as a function of ADL scores using a transitional model. The first pattern commences when sensory integration capability starts to decrease, leading to a pattern of over-integration (illusion effect). The second pattern commences when compensatory mechanisms are not sufficient to counteract the effect of the background motion, leading to direction errors in the same direction as the background motion (reverse illusion). The third pattern commences when the task requirements are too high, leading OA to implement a probabilistic strategy by tapping toward the center of the screen.

Keywords: activities of daily living; aging; elderly; interception task; sensory integration.

FIGURE 1

(A) Schematic lay-out of the stimuli for left (L), straight (S) and right (R) target’s direction of motion. The target is depicted at its appearance position as a black disc. The finger’s home position is represented by the gray disc. The solid lines represent the part of the path where the target was visible and the dashed lines represent the part of the path where the target was invisible. The horizontal line indicates where the targets disappeared after 150 ms (target has traveled 1,6 cm). (B) Depiction of the experimental display. As in A, the black and gray discs represent the starting position of the target and the home position. The gray and white squares represent the background.

FIGURE 2

Definition of the direction error according to the tap position. The direction error is the angle in degrees between the line from the target position at start to the target position at the time of tap and a line from the position of the target when it disappeared to the tap position. The direction error were assigned a negative value when, as in the example here, the hit position was to the left of the target position at the time of tap (de Dieuleveult et al., 2018).

FIGURE 3

Average direction error in degrees for YA in the original experiment (Exp1, n = 19) and in the current experiment (Exp2, n = 19), for each experimental condition (baseline, balance and counting) and for each background direction of motion (left or right) merged between the different directions of the target’s motion (horizontal velocities: −7.2, 0, and 7.2 cm/s). Error bars represent the standard error of the mean between subjects.

FIGURE 4

Average direction error in degrees for OA in the original experiment (Exp1, n = 19) and in the current experiment [Exp2, (baseline: n = 22, balance: n = 19, counting: n = 16)], for each experimental condition (baseline, balance, and counting) and for each background direction of motion (left or right) merged between the different directions of the target’s motion (horizontal velocities: −7.2, 0, and 7.2 cm/s). Error bars represent the standard error of the mean between subjects.

FIGURE 5

Illusion effect (left minus right background motion effect) in degrees for each participant in each age group [YA (n = 19), OA (baseline: n = 22, balance: n = 19, counting: n = 16)] and each experimental condition (baseline, balance, and counting). Younger adults are represented in black. Older adults are represented in gray. The white asterisks represent significant differences between the left and right background motion effect.

FIGURE 6

Average percentage of hits for each group [YA (n = 19), OA (baseline: n = 22, balance: n = 19, counting: n = 16)] and for each experimental condition (baseline, balance, and counting); averaged over the target’s motion direction (horizontal velocities: −7.2, 0, and 7.2 cm/s). Error bars represent the standard error of the mean between subjects. Significant differences are represented with asterisks in the figures; ^*p < 0.05; ^∗∗∗p < 0.001.

FIGURE 7

Graph representing the three hypothesized age-related transitions in patterns happening in the interception task. In the early phase of age-related changes (transition 1), there is a tendency to integrate all available information with a lack of proper weighting less reliable information (“over integration” pattern). In a second phase of the age-related process, OA become unable to downregulate the task-irrelevant background and are dragged by it, showing a reverse effect of the illusion (transition 2) (“dragged by the background” pattern). In a later phase of age-related changes, multisensory integration becomes too difficult, and older adults change their pattern again (transition 3), basically turning the interception task into Reaction Time task (“ minimal use of visual information” pattern).