Is Happy Facial Expression Identified by the Left or Right Hemisphere？

1IntroductionCorrectly identifying other people′s facial ex-pressions of emotions is important to human socialinteraction in all societies.Many studies suggestthat the identification of facial expressions in par-ticular and perceptual processing of emotional infor-mation is carried out mainly by the right hemi-sphere of the brain[1￣7].Damage to the righthemisphere generally produces more significant im-pairment in recognition of all facial expressions ofemotion than damage to the left hemisp…     

The effects of complexity on the perception of vibrotactile patterns presented to separate fingers

Pairs of vibrotactile patterns were presented to subjects’ left middle and index fingerpads (unilateral presentation) or left and right index fingerpads (bilateral presentation), using two Optacon arrays. A set of simple (one-line) patterns and a set of complex (two-line) patterns were constructed sothat they were equally identifiable when presented individually. In Experiment 1, discrimination performance was lower for two-line patterns than it was for one-line patterns, and it was lower for unilateral presentation than it was for bilateral presentation. Communality, the number of lines that two patterns share in common, was a major factor in reducing discrimination performance for two-line patterns. Subjects’ abilities to identify one member of the pair of patterns were measured in Experiment 2. There were no significant differences in performance between pattern sets or type of presentation when subjects attended to a single pattern. However, when subjects were required to attend to both patterns, identification performance was lower for two-line patterns than it was for one-line patterns, and it was lower for unilateral presentation than it was for bilateral presentation. The results suggest that there are limited attentional resources for processing vibrotactile patterns and that more resources are available bilaterally than are available unilaterally.     

The effects of complexity on the perception of vibrotactile patterns presented to separate fingers.

Pairs of vibrotactile patterns were presented to subjects' left middle and index fingerpads (unilateral presentation) or left and right index fingerpads (bilateral presentation), using two Optacon arrays. A set of simple (one-line) patterns and a set of complex (two-line) patterns were constructed so that they were equally identifiable when presented individually. In Experiment 1, discrimination performance was lower for two-line patterns than it was for one-line patterns, and it was lower for unilateral presentation than it was for bilateral presentation. Communality, the number of lines that two patterns share in common, was a major factor in reducing discrimination performance for two-line patterns. Subjects' abilities to identify one member of the pair of patterns were measured in Experiment 2. There were no significant differences in performance between pattern sets or type of presentation when subjects attended to a single pattern. However, when subjects were required to attend to both patterns, identification performance was lower for two-line patterns than it was for one-line patterns, and it was lower for unilateral presentation than it was for bilateral presentation. The results suggest that there are limited attentional resources for processing vibrotactile patterns and that more resources are available bilaterally than are available unilaterally.     

Lexical decisions in the right and left cerebral hemispheres

Subjects performed a lexical decision task in which letter-strings were presented unilaterally and tachistoscopically to the right and left visual fields. Four types of letter-strings were used: high frequency words, low frequency words, pronounceable nonwords, and unpronounceable nonwords. Measures of reaction time and error rate both showed a right visual field advantage for both classes of words and no difference between the hemispheres for either class of nonword. It was concluded that meaning is a more salient parameter of wordness than is pronounceability. Possible mechanisms for processing words presented to the left visual field were discussed.     

Stimulus-response compatibility and the motor system

Three experiments examined stimulus-response (S--R) compatibility relationships with the stimulus array perpendicular to the response array. In Experiments I and II, stimuli indicated right and left positions, while the responses were movements up and down. The mapping right/up and left/down was preferable for the right hand, but the reverse mapping was preferable for the left hand. In Experiment III, the stimuli indicated up and down positions, while the responses were movements to the right and left. In this case, the mapping up/left and down/right was preferable for the right hand, and the reverse mapping was preferable for the left hand. The results are most easily explained by assuming that counterclockwise rotational movements are preferable for the right hand, while clockwise is preferable for the left. These preferences are manifest through combinations of implicit movements towards the stimulus and explicit movements towards the response key. This principle is shown to provide a simpler explanation for some previously reported S-R compatibility effects.     

Asymmetries in Coupling Dynamics of Perception and Action

The influence of information-based dynamics on coordination dynamics of rhythmic movement was examined with special reference to the expression of asymmetries. In Experiment 1, right-handed subjects performed unimanual, rhythmical movements in coordination with either a discrete or continuous visual display. The right hand-visual display system defined a more stable perception-action collective than the left, particularly when continuous visual information was available. In Experiment 2, the same subjects performed rhythmic bimanual movements in coordination with a continuous visual display. The action collective was inherently more stable than the perception-action collective, although similar patterns were observed at both levels. Importantly, the dynamics of the perception-action collective impinged upon the dynamics of the action collective in terms of stability. Asymmetries remained evident between limbs in the bimanual preparations, with the left hand exhibiting greater limit-cycle variability and also a tendency to more often effect transitions at the action couple. Features of dynamical models that capture characteristics of manual asymmetries are discussed.     

Specification of movement amplitudes for the left and right hands: evidence for transient parametric coupling from overlapping-task performance

Bimanual coordination tasks suggest transient cross-talk between concurrent specification processes for movements of the left and right hand that vanishes as the time for specification increases. In 2 experiments with overlapping and successive unimanual tasks, the hypothesis of transient coupling was examined for a psychological-refractory-period paradigm. Time for specification was manipulated by varying the delay between first and second signal (Experiment 1) and by precuing the first response (Experiment 2). Participants performed rapid reversal movements of same or different amplitudes with the left and right hands. With different amplitudes, reaction times (RTs) of the second responses were longer than with same amplitudes at short delays, and this disappeared at longer delays in Experiment 1. In Experiment 2, precuing also reduced the difference between RTs of second responses in same-amplitude and different-amplitude trials. These findings are consistent with the hypothesis of transient coupling during amplitude specification obtained with bimanual tasks.     

Judgments of the duration of visually marked empty time intervals: Linking perceived duration and sensitivity

The capability of subjects to categorize (as short or long) visually marked empty time intervals was investigated in three experiments. Two visual signals, located 18° to the left (L) and to the right (R) of a fixation point in the visual field, established four marking conditions, two unilaterally presented (L-L and R-R) and two bilaterally presented (L-R and R-L). In Experiments 1 and 2, the results show that discrimination is better with unilateral sequences than with bilateral sequences and that the perceived duration is longer with an L-R than with an R-L sequence. In addition, Experiment 2 shows that, in comparison with a condition in which Markers 1 and 2 remain identical for a complete session, varying the markers from trial to trial does not decrease discrimination. Also, Experiment 2 shows that discrimination is better when both visual markers are presented at fovea than it is in the unilateral conditions. Experiment 3 shows that bilateral intervals are perceived as being longer and are better discriminated than are intervals marked by an intermodal sequence (auditory-visual or visual-auditory). The general discussion reports the implications of having different perceived duration and sensitivity levels, in various marker-type conditions, for an internal-clock hypothesis. Some implications of these results for a lateralized-timer hypothesis are also discussed.     

Semantic organization in the young child: Evidence for the development of semantic feature systems

In two experiments, 5-, 7-, 9-, and 11-year-old children and college students were presented on each trial with a sentence followed by a probe word. Their task was to indicate whether the probe was in the sentence or not. Of primary interest were the false recognitions and the correct latencies that occurred when the probe word was a synonym or antonym of one of the words in the sentence (Experiment I) or when the probe was a subordinate, superordinate, part, or whole (Experiment II). The younger children were more affected by synonymy than antonymy, although the older children and adults were not. At all ages, the categorical relationships caused more recognition confusion than the partwhole relationships. Subjects were more affected when the probe was a superordinate than when it was a subordinate, and somewhat more affected when the probe was the whole than when it was the part. These results suggest that children as young as 5 years of age have well-organized conceptual systems based on shared meaning components.     

Children's strategy preferences for resolving contradictory story information under two social conditions

This paper attempted to examine how children, when confronted with a literary implicature, resolve this implicature under two types of social conditions. More specifically, this paper identified five types of strategies which people employ to resolve text anomalies arising when old information in a story setting is incompatible with new information in a story ending. Two experiments demonstrated that third graders (8.4 and 8.6 years) and sixth graders (12.5 and 12.8 years) consistently selected certain strategies for resolving old and new, empirical and value, contradictory information. Although third and sixth graders demonstrated a similar strategy preference for resolving contradictory old and new information in formal conditions, the principal difference was that third graders modified old information to fit new information while sixth graders modified new information to fit old information. In contrasting the formal and informal conditions, third graders shifted their strategy preferences so as to minimize the amount of text restructuring in the formal condition; sixth graders, on the other hand, shifted their strategy preferences so as to maximize the amount of text restructuring in informal conditions. These findings suggest that story schema structures are more interpretive than story grammar psychologists presently assume.     

Reproducing the end location of a positioning movement: the long and short of it

Two experiments were conducted in an attempt to determine the conditions under which shifts in the starting position of a linear positioning response influenced the reproduction of the end location of movements of various lengths. In Experiment 1, response bias (i.e., shift in constant error) was affected by the direction of the shift in starting position between presentation and recall. For short (20 cm) and medium (50 cm) length movements, this relationship was evident regardless of hand used (left or right), direction of the movement (left to right or right to left), and length of the retention interval (5 or 45 s). However, no relation between response bias and the direction of the starting position shifts was apparent for long (80 cm) movements. The results of Experiment 2 in which more movement lengths were used revealed a response bias that corresponded to shifts in starting position primarily during the first few reproductions of the two shortest movements (20 and 30 cm). However, no systematic bias was evident for any length movement after three reproduction attempts. Possible strategies used by subjects to reproduce the end location of movements of various lengths were discussed.     

Perception of numerical stimuli felt by fingers of the left and right hands

Three experiments are reported in which blindfolded right-handed adults felt numerical stimuli with the middle fingers of their left or right hands. These stimuli consisted of collections of raised dots in random arrangement to be enumerated (Experiment I), collections of evenly spaced raised dots in a straight line to be enumerated (Experiment II), and raised digits to be identified (Experiment III). Differences between hands were only found in Experiment I. The left hand was faster, apparently reflecting specialisation of the right cerebral hemisphere for the analysis of complex spatial stimuli. A fourth experiment, in which collections of raised dots in random arrangement to be enumerated were felt through a piece of cloth by subjects who were not blindfolded, confirmed the left hand superiority and demonstrated that it had not arisen from loss of sight of the movements of the dominant hand.     

Visual field x response hand interactions and level priming in the processing of laterally presented hierarchical stimuli

Hemisphere-specific processing of laterally presented global and local stimulus levels was investigated by (a) examining interactions between the visual field of stimulus presentation and the response hand and (b) comparing intra- with inter-hemispheric effects of level priming (i.e. faster and more accurate performance when the target level repeats). Although in Experiment 1, which involved two-choice responses with left and right hands, performance costs occurred when the same hemisphere received the stimulus and controlled the response hand, further analyses suggest that these effects reflect spatial compatibility rather than intra-hemispheric interference. Consistent with the spatial compatibility interpretation, in Experiment 2 a similar visual field x response interaction was obtained with regard to left and right responses given with the same hand. Trial-to-trial level priming occurred in both experiments and was unaffected by the intra-hemispheric sequence of target levels. Implications regarding hemispheric processing mode are discussed.     

Impact of Handedness Consistency on Bimanual and Unimanual Continuous Movements

Bimanual coordination is an essential human function requiring efficient interhemispheric communication to produce coordinated movements. Previous research suggests a “bimanual advantage” phenomenon, where completing synchronized bimanual tasks results in less variability than unimanual tasks. Additionally, of hand dominance has been shown to influence coordinated performance. The present study examined the bimanual advantage in individuals with consistent and inconsistent handedness. It was predicted that participants with consistent handedness would not display a bimanual advantage unlike those with inconsistent handedness. Fifty-six young adults completed a finger-tapping paradigm in five conditions: unimanual tapping with either left or right hand, in-phase bimanual tapping, and out-of phase bimanual tapping led by either left or right hand. Results were not consistent with the hypothesis that participants with consistent handedness displayed the “bimanual advantage”. However, the “bimanual advantage” was not evident for the inconsistent handers when the temporal consistency was measured with either the left or right hand only. Overall, the “bimanual advantage” may be dependent upon consistency of hand preference, as well as the direction of hand dominance.     

The nonverbal mediation of self-fulfilling prophecies in interracial interaction

Two experiments were designed to demonstrate the existence of a self-fulfilling prophecy mediated by nonverbal behavior in an interracial interaction. The results of Experiment 1, which employed naive, white job interviewers and trained white and black job applicants, demonstrated that black applicants received (a) less immediacy, (b) higher rates of speech errors, and (c) shorter amounts of interview time. Experiment 2 employed naive, white applicants and trained white interviewers. In this experiment subject-applicants received behaviors that approximated those given either the black or white applicants in Experiment 1. The main results indicated that subjects treated like the blacks of Experiment 1 were judged to perform less adequately and to be more nervous in the interview situation than subjects treated like the whites. The former subjects also reciprocated with less proximate positions and rated the interviewers as being less adequate and friendly. The implications of these findings for black unemployment were discussed.     

The Simon effect with wheel-rotation responses

The authors examined clockwise and counterclockwise wheel-rotation responses to high- or low-pitched tones presented in participants' (N = 96, Experiment 1; N = 48, Experiment 2; N = 48, Experiment 3) left and right ears. In Experiment 1, a Simon effect (fastest responding when tone location and direction of wheel turn corresponded) was obtained when participants' hands were at the top or middle of the wheel but not at the bottom. With the bottom hand placement, a Simon effect was induced by instructions emphasizing hand movements but not by instructions emphasizing wheel movements (Experiment 2), and by a visual cursor controlled by the wheel but not one triggered by the response (Experiment 3). The results of the experiments showed that the nature of the task and the instructed action goal influence the direction of the Simon effect.     

Grip morphology and hand use in chimpanzees (Pan troglodytes): evidence of a left hemisphere specialization in motor skill

Three experiments on grip morphology and hand use were conducted in a sample of chimpanzees. In Experiment 1, grip morphology when grasping food items was recorded, and it was found that subjects who adopted a precision grip were more right-handed than chimpanzees using other grips. In Experiment 2, the effect of food type on grasping was assessed. Smaller food items elicited significantly more precision grips for the right hand. In Experiment 3, error rates in grasping foods were compared between the left and right hands. Significantly more errors were made for the left compared with the right hand. The cumulative results indicate that chimpanzees show a left-hemisphere asymmetry in motor skill that is associated with the use of precision grips.     

Blocking Perturbations and Multilimb Control in Rapid-Aiming Movements

The effect of an unexpected mechanical block on the control of multilimbaiming movements was studied in two experiments. In the first experiment, subjects (N = 10) attempted to push two hand levers 9 cm forward in 200 ms without vision. In the second experiment, subjects (N = 9) attempted to push hand levers and foot pedals forward 9 cm in 200 ms. After a practice period, five attempts at blocking the limb movements were made on the left lever and the right lever (Experiment 1) and on both levers (Experiment 2 only) during randomly selected trials. When one hand was blocked in Experiment 1, the other hand undershot the target on the first blocked trial, with slight reductions in movement time. When one hand was blocked in Experiment 2, the contralateral limb undershot the target on all blocked trials, but this had little effect on the lower limbs. The lower limbs undershot the target when both up- per limbs were blocked. Discrete movement corrections were made on more of the blocked trials relative to the unblocked control trials. Interlimb correlations decreased following the block, suggesting that subjects dissociated the limbs in an effort to minimize the effect of the block.     

Reproducing the End Location of a Positioning Movement

Two experiments were conducted in an attempt to determine the conditions under which shifts in the starting position of a linear positioning response influenced the reproduction of the end location of movements of various lengths. In Experiment 1, response bias (i.e., shift in constant error) was affected by the direction of the shift in starting position between presentation and recall. For short (20 cm) and medium (50 cm) length movements, this relationship was evident regardless of hand used (left or right), direction of the movement (left to right or right to left), and length of the retention interval (5 or 45 s). However, no relation between response bias and the direction of starting position shifts was apparent for long (80 cm) movements. The results of Experiment 2 in which more movement lengths were used revealed a response bias that corresponded to shifts in starting position primarily during the first few reproductions of the two shortest movements (20 and 30 cm). However, no systematic bias was evident for any length movement after three reproduction attempts. Possible strategies used by subjects to reproduce the end location of movements of various lengths were discussed.     

Inconsistent handedness and saccade execution benefit face memory without affecting interhemispheric interaction

Individuals who consistently use their dominant hand for most tasks exhibit poorer memory than individuals whose handedness is relatively inconsistent, but consistent-handers' memory can be enhanced by making repetitive saccadic eye movements before attempting retrieval. One account of these effects is that inconsistent handedness and saccade execution are associated with increased interhemispheric interaction, which putatively facilitates retrieval. We tested this account by having participants classify faces as famous or novel. Faces were presented in the left and right visual fields simultaneously (bilaterally) or in one field only (unilaterally). As in prior studies, famous faces were classified more quickly and more accurately given bilateral presentation, but novel faces were not. These bilateral gain effects indicate that interhemispheric interaction specifically facilitates famous-face recognition, and therefore larger gains may reflect greater interhemispheric interaction. However, neither inconsistent handedness nor saccade execution increased the size of bilateral gain. Inconsistent handedness and saccade execution (the latter for consistent-handers only) did increase face-classification accuracy, but the increases were not specific to famous-face recognition, and, in fact, were somewhat stronger for novel-face identification. These results extend the beneficial mnemonic effects of inconsistent handedness and saccade execution to faces, but indicate that these benefits are not caused by increased interhemispheric interaction.