Getting the closer object? An information‐based dissociation between vision for perception and vision for movement in early infancy

In human adults two functionally and neuro‐anatomically separate systems exist for the use of visual information in perception and the use of visual information to control movements (Milner & Goodale, 1995 , 2008 ). We investigated whether this separation is already functioning in the early stages of the development of reaching. To this end, 6‐ and 7‐month‐old infants were presented with two identical objects at identical distances in front of an illusory Ponzo‐like background that made them appear to be located at different distances. In two further conditions without the illusory background, the two objects were presented at physically different distances. Preferential reaching outcomes indicated that the allocentric distance information contained in the illusory background affected the perception of object distance. Yet, infants' reaching kinematics were only affected by the objects' physical distance and not by the perceptual distance manipulation. These findings were taken as evidence for the two‐visual systems, as proposed by Milner and Goodale ( 2008 ), being functional in early infancy. We discuss the wider implications of this early dissociation.     

Fitting objects into holes: on the development of spatial cognition skills

The authors examined 14- to 26-month-old infants' understanding of the spatial relationships between objects and apertures in an object manipulation task. The task was to insert objects with various cross-sections (circular, square, rectangular, ellipsoid, and triangular) into fitting apertures. A successful solution required the infant to mentally rotate the object to be fit into the aperture and use that information to plan the action. The object was presented standing up in half of the trials; in the other half, it was lying down. The results showed that infants solved the problem consistently from age 22 months and that a successful solution was associated with appropriate preadjustments before the hand arrived with the block to the aperture. No sex differences were found.     

Predictive tracking over occlusions by 4-month-old infants

Two experiments investigated how 16-20-week-old infants visually tracked an object that oscillated on a horizontal trajectory with a centrally placed occluder. To determine the principles underlying infants' tendency to shift gaze to the exiting side before the object arrives, occluder width, oscillation frequency, and motion amplitude were manipulated resulting in occlusion durations between 0.20 and 1.66 s. Through these manipulations, we were able to distinguish between several possible modes of behavior underlying 'predictive' actions at occluders. Four such modes were tested. First, if passage-of-time determines when saccades are made, the tendency to shift gaze over the occluder is expected to be a function of time since disappearance. Second, if visual salience of the exiting occluder edge determines when saccades are made, occluder width would determine the pre-reappearance gaze shifts but not oscillation frequency, amplitude, or velocity. Third, if memory of the duration of the previous occlusion determines when the subjects shift gaze over the occluder, it is expected that the gaze will shift after the same latency at the next occlusion irrespective of whether occlusion duration is changed or not. Finally, if infants base their pre-reappearance gaze shifts on their ability to represent object motion (cognitive mode), it is expected that the latency of the gaze shifts over the occluder is scaled to occlusion duration. Eye and head movements as well as object motion were measured at 240 Hz. In 49% of the passages, the infants shifted gaze to the opposite side of the occluder before the object arrived there. The tendency to make such gaze shifts could not be explained by the passage of time since disappearance. Neither could it be fully explained in terms of visual information present during occlusion, i.e. occluder width. On the contrary, it was found that the latency of the pre-reappearance gaze shifts was determined by the time of object reappearance and that it was a function of all three factors manipulated. The results suggest that object velocity is represented during occlusion and that infants track the object behind the occluder in their 'mind's eye'.     

Action in development

It is argued that cognitive development has to be understood in the functional perspective provided by actions. Actions reflect all aspects of cognitive development including the motives of the child, the problems to be solved, and the constraints and possibilities of the child's body and sensorimotor system. Actions are directed into the future and their control is based on knowledge of what is going to happen next. Such knowledge is available because events are governed by rules and regularities. The planning of actions also requires knowledge of the affordances of objects and events. An important aspect of cognitive development is about how the child acquires such knowledge.     

The power distance reduction hypothesis on a level of reality

An experiment and a replication were conducted, testing the hypothesis that the smaller the actual power distance between a subject and a more powerful other, the stronger the tendency to reduce the power distance between them. Power distance was created by placing the subject in a group of three people plus a supervisor. In the condition of large power distance, the three workers had identical functions. Small power distance was induced by placing the subject at an intermediary power level, above the two workers, but below the supervisor. Two other conditions of small power distance were manipulated in order to assess the effects of the timing of power promotion and the perception of the promotion as caused by the subject's task competence. During the course of the experiment, the supervisor left unexpectedly and the subject had the option of taking over the supervisory role or letting one of his co-workers assume it. In the first experiment, subjects who were at a large power distance chose to replace the supervisor significantly less frequently than subjects in the three small power-distance conditions. The small power-distance conditions did not differ from each other. The replication with two small power-distances conditions produced the same results. Both experiments took place in a natural setting.     

Proximal velocity change as a determinant of space perception

How and to what degree does proximal velocity change determine perceived translatory motion in depth? This question was studied with a stimulus consisting of a single dot, moving in a straight horizontal path in a frontoparallel plane. Its motion corresponded to distai depth motion with constant speed. Ss reported verbally what they perceived. The results show that proximal velocity changes of this kind are, within certain limits, utilized by the visual system for the perception of translatory motion in depth. The limits were found to be determined by the absolute rate of change in proximal velocity. Further, it was found that the perceived motion track was usually bent, although all stimuli simulated depth motions along straight paths.     

Using mu rhythm desynchronization to measure mirror neuron activity in infants

The Mirror Neuron System hypothesis stating that observed actions are projected onto the observer’s own action system assigns an important role to development, because only actions mastered by the observer can be mirrored. The purpose of the present study was to investigate whether there is evidence of a functioning mirror neuron system (MNS) in 8-month-old infants. High-density EEG was used to assess the mu rhythm desynchronization in an action observation task where the infants observed a live model. To reduce noise, ICA decompositions were used. The results show a higher desynchronization of the mu rhythm when infants observed a goal-directed action than when they observed a spatially similar non-goal-directed movement. The localizations of the sources are in agreement with those proposed by the MNS hypothesis. This indicates that the MNS is functioning at this age.     

Hemispheric asymmetry and human associative learning: Interactions with attention

In a previous study (Hugdahl & Brobeck, 1986) it was shown that Pavlovian conditioning to an auditory verbal conditioned stimulus (CS) initially presented only to the left cerebral hemisphere was stronger than when the same CS was presented to the right hemisphere. This was followed up in the present study by controlling for the possibility that the effect was caused by laterally biased attention. The study was performed using the “dichotic extinction paradigm,” which consists of three different phases. During the habituation phase, the CS+ and CS- were presented binaurally and separated in time. During the acquisition phase, the CS+ was followed by a white-noise unconditioned stimulus (UCS). During the dichotic extinction phase, the CS+ and CS- were presented dichotically, i.e., simultaneous presentations on each trial. Half of the subjects had the CS+ in the right ear, and half had the CS+ in the left ear. Each group was further divided into two subgroups, with one subgroup instructed to attend only to the right ear input, and the other subgroup to attend only to the left ear input. During acquisition, larger electrodermal responses were obtained to the CS+ than to the CS-. During dichotic extinction, the CS+ right ear group showed superior resistance to extinction compared to the CS+ left ear group, with no effect of the manipulation of attention. The effect was, however, attenuated when levels of acquisition was used as covariates in an analysis of covariance. There were overall larger responses from the left hand recording.