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Biomedical subjects

Gustaf Gredebäck

Publications and source records attributed to Gustaf Gredebäck.

6 recordsLinked to original sources

Learning about occlusion: initial assumptions and rapid adjustments.

We examined 6-month-olds abilities to represent occluded objects, using a corneal-reflection eye-tracking technique. Experiment 1 compared infants' ability to extrapolate the current pre-occlusion trajectory with their ability to base predictions on recent experiences of novel object motions. In the first condition infants performed at asymptote ( approximately 2/3 accurate predictions) from the first occlusion passage. In the second condition all infants initially failed to make accurate prediction. Performance, however, reached asymptote after two occlusion passages. This is the first study that demonstrates such rapid learning effects during an occlusion task. Experiment 2 replicates these effects and demonstrates a robust memory effect extending 24h. In occlusion tasks such long-term memory effects have previously only been observed in 14-month-olds (Moore & Meltzoff, 2004).

Adaptation, Psychological↗

Infants predict other people's action goals.

Do infants come to understand other people's actions through a mirror neuron system that maps an observed action onto motor representations of that action? We demonstrate that a specialized system for action perception guides proactive goal-directed eye movements in 12-month-old but not in 6-month-old infants, providing direct support for this view. The activation of this system requires observing an interaction between the hand of the agent and an object.

Adult↗

The development of reactive saccade latencies.

Saccadic reaction time (SRT) of 4-, 6- and 8-month-old infants' was measured during tracking of abruptly changing trajectories, using a longitudinal design. SRTs decreased from 595 ms (SE=30) at 4 months of age to 442 ms (SE=13) at 8 months of age. In addition, SRTs were lower during high velocities (comparing 4.5 and 9 degrees/s) and vertical (compared to horizontal) saccades.

Age Factors↗

Developmental asymmetries between horizontal and vertical tracking.

The development of the asymmetry between horizontal and vertical eye tracking was investigated longitudinally at 5, 7, and 9 months of age. The target moved either on a 2D circular trajectory or on a vertical or horizontal 1D sinusoidal trajectory. Saccades, smooth pursuit, and head movements were measured. Vertical tracking was found to be inferior to horizontal tracking at all age levels. The results also show that the mechanisms responsible for horizontal and vertical tracking mutually influence one another in the production of 2D visual pursuit. Learning effects were observed within-trials but no transfer between trials was found.

Child Development↗

Inferring causality assessments from predictive responses: cue interaction without cue competition.

The authors criticize the use of participants' predictive responses during a learning phase as a measure of causal assessments. Simulations demonstrate that a general aim to minimize error as required in the prediction task will produce results in accordance with those observed, in particular apparent cue interaction effects. It is argued that measures estimated from prediction responses do not reflect causal ratings, but are side-effects of learning explained by adaptation in strategy to changes in presented cell frequencies. The results are reinterpreted to be in line with a causal model view, not requiring dual processes or cue competition of lower level associative processes.

Association Learning↗

The development of two-dimensional tracking: a longitudinal study of circular pursuit.

We investigated 6- to 12-month-old infants' ability to track an object moving on circular trajectories, using a longitudinal design. Consistent predictive gaze tracking was not found before 8 months of age. These results indicate that infants' horizontal and vertical components of circular tracking are less mature than expected from previous studies of one-dimensional horizontal tracking. Vertical components are especially immature, particularly during high velocity tracking (approximately 20 degrees /s). The results also suggest that horizontal and vertical tracking are mutually dependent during early development. Saccades were predictive (average lag >-125 ms) from 6 months onwards.

Aging↗