Eye remember you two: gaze direction modulates face recognition in a developmental study

The effects of gaze direction on memory for faces were studied in children from three different age groups (6-7, 8-9, and 10-11 years old) using a computerized version of a task devised by Hood, Macrae, Cole-Davies and Dias (2003). Participants were presented with a sequence of faces in an encoding phase, and were then required to judge which faces they had previously encountered in a surprise two-alternative forced-choice recognition test. In one condition, stimulus eye gaze was either direct or deviated at the viewing phase, and eyes were closed at the test phase. In another condition, stimulus eyes were closed at the viewing phase, with either direct or deviated gaze at the test phase. Modulation of gaze direction affected hit rates, with participants demonstrating greater accuracy for direct gaze targets compared to deviated gaze targets in both conditions. Reaction times (RT) to correctly recognized stimuli were faster for direct gaze stimuli at the viewing phase, but not at the test phase. The age group of participants differentially affected these measures: there was a greater hit rate advantage for direct gaze stimuli in older children, although RTs were less affected by age. These findings suggest that while the facilitation of face recognition by gaze direction is robust across encoding and recognition stages, the efficiency of the process is affected by the stage at which gaze is modulated.     

Episodic temporal generalization: a developmental study.

Groups of 5-year-olds, 10-year-olds, and adults completed either an episodic temporal generalization task, in which no stimuli were repeated, or a repeated standard temporal generalization task, in which there was a fixed standard that was repeated on every trial. Significant developmental improvements were found on both tasks. In both tasks, gradients of performance over two different stimulus ranges superimposed well when plotted on the same relative scale. Performance was similar for the adults and 10-year-olds across tasks, but the 5-year-olds performed better on the repeated standard task. These findings suggest that perceptual processes are a source of scalar variability in timing, and that there are developmental changes in levels of such variability.     

Mechanisms of attention: a developmental study

A model of selective attention is proposed which contains a number of properties. First, stimuli which are irrelevant to the subjects' task can be analyzed to semantic levels automatically, and such stimuli can produce intrusion/interference effects. Second, two mechanisms by which selection is achieved are habituation to, and inhibition of, these irrelevant stimuli. A series of studies demonstrates that both the ability to process automatically irrelevant stimuli and the habituation mechanisms of attention are observable by Grade 2, whereas the inhibitory mechanism is not always evident at this stage. It is suggested that the greater distractability of children in certain situations may be due in part to the underutilization of this inhibitory mechanism. We further propose that children may be able to employ inhibitory mechanisms in more familiar perceptual-motor tasks.     

Interposition and size constancy: a developmental study

27 children (mean age 6.7 yr.) and 84 adults (mean age 26.3 yr.) were asked to judge the sizes of human figures in photographs. Half the cards contained interpositional depth cues while the other half did not. Both groups of subjects showed better size constancy with interposition present than without it.     

Timing and accuracy of visually directed movements in children: control of direction and amplitude components

The reaction times (RTs), movement times (MTs), and final accuracy of hand movements directed towards visual goals were measured in 6-, 8-, and 10-year-old children, using tasks in which direction and amplitude components of movement were distinctly required. The tasks were performed with and without visual feedback of the limb. RTs decreased with age, and were shorter in directional than in amplitude task, in all ages. MTs were the longest at age 8 in both tasks, equally short at ages 6 and 10 in the directional task, the shortest at age 10, and intermediate at age 6, when amplitude had to be regulated. In the amplitude task, the target distance generally affected MTs under both visual conditions, but to a lower degree at age 10 than in the two younger groups. Movement accuracy, which was in all cases higher with visual feedback, showed different developmental trends among the two spatial components: directional accuracy was not different among the three groups of age, whereas amplitude accuracy showed a nonmonotonic development in the nonvisual condition, with an increase between age 6 and age 10, and the lowest level at age 8. In the visual condition, amplitude accuracy did not change with age. The specification of direction seems therefore to predominantly load the preparatory stage of the response. Amplitude specification seems to be more dependent on on-going regulations and to undergo a longer and more complex development, with a critical period around age 8 when a greater propensity for a feedback-based control appears on the two components. With increasing age, amplitude tends to be specific to a greater extent by a feedforward process.     

Auditory attention switching: a developmental study

The developmental course of the ability to rapidly allocate attention was studied using a dichotic listening task with 8-year old, 11-year old and college age subjects. In this task, subjects were instructed to listen to one ear for predescribed targets and then were later signaled (on some trials) to switch their attention to the other ear. Reorientation was assessed by comparing the pattern of subjects' omission and intrusion errors on trials following a command to switch ears with the pattern of errors on no-switch trials. Older subjects were better able to reallocate their attention in accordance with task demands, with the greatest gains in performance occurring between ages 8 and 11. This developmental change appears to be generally continuous and quantitative in nature. Since successful performance of this task requires flexibility in subjects' ability to control their focus of attention, these results support the hypothesis that the basis of the developmental improvement in the ability to ignore irrelevant information is linked to the ability to use active attentional strategies.     

fMRI of developmental stuttering: a pilot study

The purpose of this investigation was to explore the feasibility of fMRI in the study of developmental stuttering. Speech contrasts (loud versus silent reading) and language contrasts (reading of semantically meaningful text versus nonsense words) of six developmental stutterers and six nonstutterers were compared using a commercial 1 Tesla MR-Scanner (Siemens Expert). Results indicate that mapping cortical function in persons who stutter is indeed feasible, even with a 1TMR-system. Compared to normals the stutterers seemed to employ different and particularly less differentiated auditory and motor feedback strategies in speech. They apparently rely on auditory processing and on cerebellar contribution as much during silent reading as during reading aloud. Moreover, they showed a greater involvement of the right hemisphere in language processing, activating not only the typical language areas on the left but also and with equal magnitude the right side homologues of these areas. In spite of the promising results, at present several practical problems such as possible movement artifacts and possible masking through scanner noise still hamper a more straightforward use of fMRI in the study of developmental stuttering.     

Cognitive factors in simple reactions: a developmental study

In an exploration of factors underlying the developmental increase in the speed of simple reaction to an auditory stimulus, two experiments were undertaken, with subjects aged 4, 10, and 20. The first experiment demonstrated that provision of visual feedback caused improvement for younger subjects but not for adults, whereas neither practice nor variable feedback caused any differential change. The second experiment was a simulated game where visual feedback was contingent on a "hit" on the previous trial. Following a hit the target moved faster, following a miss, slower. Practice caused a considerable improvement for the 4-year old subjects, but not for the older subjects. The nature it or miss feedback on the previous trial had powerful effects on the simple reaction times. For all subjects, a miss resulted in a subsequent substantial increase in speed on the next trial. Following a hit, the adults were unaffected, but the youngest subjects were substantially slower. The results are interpreted in terms of inappropriate relaxation following a hit for the 4-year old subjects, with active strategic behavior by the adults, following a miss. It is concluded that one variable (incentive provided by a miss) affects simple reaction for all ages, that two (disincentive provided by a hit, and visual feedback) differentially affect subjects of different ages, and that a fourth (use of a "trade-off" strategy) is not available to the youngest subjects.     

Switching between tasks and responses: a developmental study

Task switching requires the ability to flexibly switch between task rules and responses, and is sensitive to developmental change. We tested the hypothesis that developmental changes in task switch performance are associated with changes in the facilitating or interfering effect of the previously retrieved stimulus-response (S-R) association. Three age groups (7-8-year-olds, 10-12-year-olds and 20-25-year-olds) performed a two-choice reaction time (RT) task in which spatially compatible or incompatible responses were required. The RT costs associated with switching between tasks were larger when responses were repeated than when responses were alternated. Younger children showed a greater cost than adults when switching between tasks but repeating responses. This age difference decreased when the interval between the previous response and the upcoming stimulus increased. Switch costs were larger when switching to the compatible task than to the incompatible task, but this effect did not differ between age groups. These findings suggest that young children build up stronger transient associations between task sets and response sets, which interfere with their ability to switch to currently intended actions. A similar pattern has previously been observed for older adults (Mayr, 2001), suggesting a common contributor to task switching deficits across the life span.     

Anticipation of tennis-shot direction from whole-body movement: The role of movement amplitude and dynamics

While recent studies indicate that observers are able to use dynamic information to anticipate whole-body actions like tennis shots, it is less clear whether the action’s amplitude may also allow for anticipation. We therefore examined the role of movement dynamics and amplitude for the anticipation of tennis-shot direction. In a previous study, movement dynamics and amplitude were separated from the kinematics of tennis players’ forehand groundstrokes. In the present study, these were manipulated and tennis shots were simulated. Three conditions were created in which shot-direction differences were either preserved or removed: Dynamics-Present–Amplitude-Present (D^PA^P), Dynamics-Present–Amplitude-Absent (D^PA^A), and Dynamics-Absent–Amplitude-Present (D^AA^P). Nineteen low-skill and 15 intermediate-skill tennis players watched the simulated shots and predicted shot direction from movements prior to ball-racket contact only. Percent of correctly predicted shots per condition was measured. On average, both groups’ performance was superior when the dynamics were present (the D^PA^P and D^PA^A conditions) compared to when it was absent (the D^AA^P condition). However, the intermediate-skill players performed above chance independent of amplitude differences in shots (i.e., both the D^PA^P and D^PA^A conditions), whereas the low-skill group only performed above chance when amplitude differences were absent (the D^PA^A condition). These results suggest that the movement’s dynamics but not their amplitude provides information from which tennis-shot direction can be anticipated. Furthermore, the successful extraction of dynamical information may be hampered by amplitude differences in a skill-dependent manner.     

Sampling frequency and the study of eye-hand coordination in aiming

This study synchronized sampling of point of gaze (PG) and hand movements in a fast aiming task, using a 60- and a 120-Hz sampling frequency. The subjects moved eyes, head, hand, and trunk freely. For limb kinematics, a significant difference between sampling conditions was only found for the number of accelerations in the profile following peak velocity of the hand. For PG movements, no differences were found for initiation time, saccade angle, fixation duration, and overall number of saccades. However, significant differences were observed for saccade duration. Previously, an invariant feature was found for the ratio of PG and hand response times (50%). For both sampling frequencies, a significant correlation and, thus, temporal coupling was found between PG response time and time to peak acceleration for the hand. Depending on the measures required, a 60-Hz sampling of PG and hand movements may provide as meaningful results as a 120-Hz sampling.     

Movement control in a reciprocal tapping task: a developmental study

A cross-sectional approach was used to replicate and examine developmental flexibility in eye-hand relationships during alternate tapping performance. A group of 68 male subjects, 34 younger (mean 75.6 months) and 34 older (mean 128.9 months) practiced 12 5-sec trials of alternate tapping in one of three accuracy conditions. Trials 2 and 11 were filmed to determine the eye movement index (EMI), a fraction relating eye movements (numerator) to alternate taps (denominator). Fractional EMI values close to 1 were labelled discontinuity and values closer to 0 (1/N) continuity. Accuracy variation tested the flexibility of EMI for developmental change, revealing that EMIs for older subjects were more continuous than for younger subjects at trial 11, but not at trial 2. Level of EMI was related to age and condition, while change in EMI due to practice was related to age. The data showed EMI strategy flexibility increased with age, and that faster tapping was afforded by less direct visual monitoring of the hand.     

Syntactics of interpretation of negation: a developmental study

Two cues are considered as syntactic indicators of the focus of a sentential negation in 7- and 10-year-olds and adults. One is the articles; it is proposed that an indefinite noun phrase is taken within the scope of a negative and a definite noun phrase outside it. A second cue is position. Based on R. S. Jackendoff's (1969, Foundations of Language, 5, 218-241) and P. A. Hornby's (1971, Child Development, 42, 1975-1988) work, subjects may be expected to take the second noun within the focus of sentential negatives regardless of the articles. In Experiments 1 and 2, subjects made picture selections for sentences of the form A/the Noun1 isn't V-ing the/a Noun2 and their passives. In Experiment 3, 10-year-olds describe the scenes of the sentences of the prior experiments. Noun position and article independently influenced the focus of the negation with age trends. Developmental differences in the uses of the articles are related to the acquisition of mastery of these linguistic markers.     

Finding parts within figures: a developmental study

Preschool children, primary school children, and unschooled adults were tested on the part-probe task designed by Palmer. Relatively high scores were obtained with all groups on parts which had a 'good' relationship with the figure. However, the ability to find more deeply embedded segments was not present in the preschool children or in the unschooled adults. This indicates that the processes of postperceptual analysis necessary to find a part in a figure are neither built-in nor the consequence of mere cognitive growth, but depend on the instruction or experience usually provided in school. Such processes should not be confused with those that lead to form perception. Inspection of the part-figure pairs and of the corresponding detection scores suggests the importance of several stimulus properties.     

Eye-hand coordination in goal-directed aiming.

In a number of studies, we have demonstrated that the spatial-temporal coupling of eye and hand movements is optimal for the pickup of visual information about the position of the hand and the target late in the hand's trajectory. Several experiments designed to examine temporal coupling have shown that the eyes arrive at the target area concurrently with the hand achieving peak acceleration. Between the time the hand reached peak velocity and the end of the movement, increased variability in the position of the shoulder and the elbow was accompanied by a decreased spatial variability in the hand. Presumably, this reduction in variability was due to the use of retinal and extra-retinal information about the relative positions of the eye, hand and target. However, the hand does not appear to be a slave to the eye. For example, we have been able to decouple eye movements and hand movements using Müller-Lyer configurations as targets. Predictable bias, found in primary and corrective saccadic eye movements, was not found for hand movements, if on-line visual information about the target was available during aiming. That is, the hand remained accurate even when the eye had a tendency to undershoot or overshoot the target position. However, biases of the hand were evident, at least in the initial portion of an aiming movement, when vision of the target was removed and vision of the hand remained. These findings accent the versatility of human motor control and have implications for current models of visual processing and limb control.     

Working memory: a developmental study of phonological recoding

A cross-sectional study using children aged 3 to 7 years and a cross-sequential study using children aged between 5 and 8 years showed that the development of phonological recoding in working memory was more complex than the simple dichotomous picture portrayed in the current literature. It appears that initially children use no strategy in recall, which is proposed to represent the level of automatic activation of representations in long-term memory and the storage capacity of the central executive. This is followed by a period in which a visual strategy prevails, followed by a period of dual visual-verbal coding before the adult-like strategy of verbal coding finally emerges. The results are discussed in terms of three working memory models (Baddeley, 1990; Engle, 1996; Logie, 1996) where strategy use is seen as the development of attentional processes and phonological recoding as the development of inhibitory mechanisms in the central executive to suppress the habitual response set of visual coding.