Association of height and weight with second to fourth digit ratio (2D:4D) and sex differences

Sex difference in 2D:46 digit ratio was studied in 386 right-handed students. The lengths of index (2D) and ring (4D) fingers were measured using a caliper. Height and weight of participants were recorded. Body height correlated negatively with right- and left-hand digit ratios in the total sample (N = 386); correlations were significant for the left-hand digit ratio of men and for the right-hand digit ratio of women (no significant correlations with weight). Males had a significantly lower 2D:4D ratio than females. After controlling for height, sex differences in right- and left-hand digit ratios completely disappeared. The results suggest that height of adults reflecting prenatal hormone status may play a role in differences between men and women in 2D:4D digit ratio for right-handers.     

Digit ratios (2D:4D and other) and relative thumb length: a test of developmental stability

Sex and side differences in relative thumb length of children and adolescents have been reported by prior researchers. These findings mirror those reported for the second-to-fourth digit ratio (2D:4D), a likely biomarker for the organizational (permanent) effects of prenatal androgens on the human brain and body. The present study investigated relative thumb length, in particular, its associations with all possible digit ratios (2D:3D, 2D:4D, 2D:5D, 3D:4D, 3D:5D, and 4D:5D), in a sample of young adults (60 men and 64 women). Relative thumb length was less precisely measurable than direct or image-based finger-length measurements, as used in digit ratio research. There were no significant sex or side differences in relative thumb length. Contrary to expectation, thumb size was not positively correlated with any digit ratios. Relative thumb length appears to be developmentally unstable (decreases during childhood and adolescence). Additional findings, such as the magnitude ranking of sex differences in digit ratios and the comparability of direct versus image-based finger-length measurements, are also discussed.     

The relationship between auditory temporal processing,phonemic awareness,and reading disability

Recent research suggests an auditory temporal deficit as a possible contributing factor to poor phonemic awareness skills. This study investigated the relationship between auditory temporal processing of nonspeech sounds and phonological awareness ability in children with a reading disability, aged 8-12 years, using Tallal's tone-order judgement task. Normal performance on the tone-order task was established for 36 normal readers. Forty-two children with developmental reading disability were then subdivided by their performance on the tone-order task. Average and poor tone-order subgroups were then compared on their ability to process speech sounds and visual symbols, and on phonological awareness and reading. The presence of a tone-order deficit did not relate to performance on the order processing of speech sounds, to poorer phonological awareness or to more severe reading difficulties. In particular, there was no evidence of a group by interstimulus interval interaction, as previously described in the literature, and thus little support for a general auditory temporal processing difficulty as an underlying problem in poor readers. In this study, deficient order judgement on a nonverbal auditory temporal order task (tone task) did not underlie phonological awareness or reading difficulties.     

Speech Rate Estimates,Language of Schooling and Bilingual Digit Span

Bilinguals obtain larger digit spans in the language in which speech rate is fastest. This effect is generally interpreted as support for a central tenet of working memory theory, which proposes subvocal rehearsal rate as an influential determinant of memory span. Variation in the method of speech rate estimation, however, has been high, making comparison between studies difficult. In the present study, we compared the predictive power of three estimates of speech rate in relation to auditory digit span for two distinct bilingual types across nine school grades (1–9). One type spoke Swedish in the home and school (SS), the other spoke Finnish in the home and Swedish at school (FS). The results showed SS consistently obtained faster speech rates in Swedish, whereas FS obtained shorter articulation and numeral reading times in Swedish, as did grades 1–3 on a digit word reading task. However, FS grades 4–9 obtained equivalent digit word reading times between the languages. SS obtained a larger digit span in Swedish than Finnish, whereas FS obtained an equivalent digit span between the languages. Thus the results indicated that memory span was mediated by factors other than phonological loop functioning, as articulation time did not predict memory span performance for FS. The finding that FS obtained lower digit spans in Swedish relative to SS suggested that the former were disadvantaged in the processing of digits compared to native speakers of the language of schooling.     

Rate and variability of finger tapping as measures of lateralized concurrent task effects

Using a sample of 48 normal right-handed adults, we assessed the effects of oral reading on concurrent unimanual finger tapping under all combinations of instructional set (speeded vs. consistent tapping), tapping movement (repetitive vs. alternating), task emphasis (reading emphasized vs. tapping emphasized), and tapping hand. Change in tapping rate and variability was measured relative to the corresponding single task control condition. Reading decreased the rate of speeded finger tapping but increased the rate of consistent tapping. In both instances, the right hand was affected more than the left hand. Asymmetries were comparable for repetitive and alternating tapping. When measured in terms of variability, however, effects were largely symmetric. The findings clarify the conditions under which lateralized concurrent task effects are most likely to occur and show that such effects are not statistical artifacts. It appears that subjects attempt to coordinate the timing of concurrent activities and that speech timing is more strongly linked to right-hand control than to left-hand control in right-handers.     

Autonomic and behavioral evidence of "implicit" memory in amnesia

A profoundly amnesic patient with a left retrosplenial-fornix lesion was tested on a recognition task that evaluated both verbal and electrodermal aspects of new learning. In addition, "implicit memory" tasks (mirror reading and perceptual identification) were given. The patient displayed strong evidence of learning on all tasks although the results of this learning were not represented in explicit recall or recognition. These findings suggest that autonomic as well as behavioral evidence can index spared memory functions in amnesia. The specific meaning of electrodermal recognition and its possible place in the distinction between implicit and explicit memory is discussed.     

Effect of slow movement execution on cognitive function

We investigated the effect of slow paced movement on cognitive function. The task movement was a dual-task performance composed of a continuous forearm rotation for the right hand and a simple reaction task for the left hand. Exp. 1 was designed to compare reaction time during performance at a slow pace to that at medium pace by 14 female undergraduate students. The mean reaction time for the left hand under the Slow Pace was significantly longer than that under the Middle Pace condition (p < .05), which showed that the subjects were required to give more attention to right-hand performance at the slow pace as it was difficult. Exp. 2 examined changes in reaction time when using the left hand that were associated with the learning of a slow paced task while using the right hand. Twenty-three female undergraduate students participated and repeated the task 6 times. The 3 sec. prior to and the 3 sec. after each auditory stimulus were used to establish rotation speed and mean coefficients of variation. The mean coefficients of variation, evaluated as within-subject variability, showed a significantly positive correlation with reaction time at Trials 1 and 6 for prestimulus and Trials 5 and 6 for poststimulus. Over successive trials participants continued performing the primary forearm task at a constant slow pace before and after receiving auditory stimuli, and this progress was related to a decrease in reaction time. Further, the sense of concentration evaluated by the subjects poststimulus was significantly higher than that prestimulus (p < .01). Performance at a constant speed, which was much slower than the ordinary or preferred speed of each subject, may have had a strong effect on their ability to remain conscious of movement execution.     

Spatial specificity of tactile enhancement during reaching

Tactile signals on a hand that serves as movement goal are enhanced during movement planning and execution. Here, we examined how spatially specific tactile enhancement is when humans reach to their own static hand. Participants discriminated two brief and simultaneously presented tactile stimuli: a comparison stimulus on the left thumb or little finger from a reference stimulus on the sternum. Tactile stimuli were presented either during right-hand reaching towards the left thumb or little finger or while holding both hands still (baseline). Consistent with our previous findings, stimuli on the left hand were perceived stronger during movement than baseline. However, tactile enhancement was not stronger when the stimuli were presented on the digit that served as reach target, thus the perception across the whole hand was uniformly enhanced. In experiment 2, we also presented stimuli on the upper arm in half of the trials to reduce the expectation of the stimulus location. Tactile stimuli on the target hand, but not on the upper arm, were generally enhanced, supporting the idea of a spatial gradient of tactile enhancement. Overall, our findings argue for low spatial specificity of tactile enhancement at movement-relevant body parts, here the target hand.     

Left-handedness and achievements in foreign language studies

Studies of brain lateralization lend support to the hypothesis that language-motor functions in left-handers are differently organized from those in right-handers. However, the implications of these differences regarding cognitive functioning are as yet subject to controversy. This concerns all hypotheses raised and empirical data collected over the years. Although it was suggested that left-handers are at higher risk of having language and reading deficits, empirical data from clinical and nonclinical populations are inconclusive at the present time. No effort, however, has been invested in examining possible differences in academic studies of foreign languages according to handedness. Here we report data indicating inferior achievements of left-handed native Hebrew speakers in studies of English as a foreign language. Left-handed pupils significantly more than right-handers were placed in lower level English classes and had more difficulties in applying orthographic-phonological mapping rules in reading English words and pseudowords. However, left-handers' difficulties in this task were not correlated with their performance in a word recognition task. It is thus suggested that the "common symptom" of poor word reading in left-handers indicates different processing failures in different left-handers, some of which impede the buildup of an internal representational system of mapping orthography to phonology and some of which concern mainly the precision of word production.     

Digit ratio as an indicator of numeracy relative to literacy in 7‐year‐old British schoolchildren

A great deal of recent research has focused upon the relationship between a hypothesized index of prenatal testosterone exposure, digit ratio and health, social and cognitive functioning. Many inconsistencies within the pattern of findings have been identified in the relationship between digit ratio and absolute levels of cognitive ability. Recent research has identified a relationship between digit ratio and basic numeric competency. This basic numerical competency has been argued to be influenced by biological factors. The present study extended this finding to academic assessment, namely the Standardized Assessment Tests undertaken in numeracy and literacy by children in the UK at the age of 7. The present study hypothesized that digit ratio would correlate with the relative difference between numeracy and literacy abilities. Digit ratios were calculated for 75 (mainly Caucasian) children aged between 6 and 7 attending a state funded infant school. The digit ratios were then correlated with the results from their National Standard Assessment Tests (SATs). A significant correlation was found as hypothesized. Additionally, there was a negative correlation between digit ratio and numeracy for males (indicating higher prenatal testosterone exposure related to higher numeracy SAT scores) and a positive correlation between digit ratio and literacy for females (indicating lower prenatal testosterone exposure related to higher literacy SAT scores). These effects were small and the implications for using digit ratio to facilitate understanding of hormonal influences upon academic attainment are discussed.     

Note on hand use in the manipulation of joysticks by rhesus monkeys (Macaca mulatta) and chimpanzees (Pan troglodytes)

In a recent article MacNeilage, Studdert-Kennedy, and Lindblom (1987) proposed that nonhuman primate handedness may be contingent on the specific task requirements with visual-spatial tasks yielding left-hand preferences and fine motor tasks producing right-hand preferences. This study reports hand preferences in the manipulation of joysticks by 2 rhesus monkeys (Macaca mulatta) and 3 chimpanzees (Pan troglodytes). Reach data were also collected on these same subjects and served as a basis for comparison with preference data for manipulation of the joystick. The data indicated that all 5 subjects demonstrated significant right-hand preferences in manipulating the joystick. In contrast, no significant hand preferences were found for the reach data. Reaction time data also indicated that the right hand could perform a perceptual-motor task better than the left hand in all 5 subjects. Overall, the data indicate that reach tasks may not be sensitive enough measures to produce reliable hand preferences, whereas tasks that assess fine motor control produce significant hand preferences.     

Individual differences in digit span, susceptibility to proactive interference, and aptitude/achievement test scores

Individual differences in digit span, susceptibility to proactive interference, and various aptitude/achievement test scores were investigated in two experiments with adults. Susceptibility to proactive interference was estimated from performance in a position task in Experiment 1, and from the Brown-Peterson task in Experiment 2. In contrast to previous research, digit span was strongly correlated with many of the aptitude/achievement scores in both experiments, suggesting that the digit span task taps some important components of mental ability. The results of both experiments were also consistent in offering no support for the hypothesis that susceptibility to proactive interference is an important source of span differences. Finally, the results of Experiment 2 suggest that susceptibility to proactive interference is a source of individual differences in reading comprehension and knowledge of word meanings, but not in grammar and word usage skills, reading rate, or quantitative ability.     

Auditory repetition priming is impaired in pure alexic patients

Alexia without agraphia, or "pure" alexia, is an acquired impairment in reading that leaves writing skills intact. Repetition priming for visually presented words is diminished in pure alexia. However, it is not possible to verify whether this priming deficit is modality-specific or modality independent because reading abilities are compromised. Hence, auditory repetition priming was assessed with lexical decision and word stem completion tasks in pure alexic patients with lesions in left inferior temporal-occipital cortex and the splenium. Perceptually based, modality-specific priming models predict intact auditory priming, since auditory association cortex is spared in the patients. Alternatively, modality-independent models, which suggest that priming reflects the temporary modification of an amodal system, might predict impairments. Baseline performance was matched in the patients and controls, although lexical decision priming measures showed an interaction between group and repetition lag. The patients showed intact immediate priming but significantly less priming than controls at longer delays. Furthermore, word stem completion priming was abolished in the patients. One explanation for the deficit is that left inferior temporal-occipital cortex supports amodal aspects of priming, as suggested by recent neuroimaging results. Another possibility is that long-term auditory priming relies on covert orthographic representations which were unavailable in the patients. The results provide support for interactive models of word identification.     

Is handedness just response bias?

Although most people prefer to use the right hand for unimanual tasks, it is unknown whether handedness arises from response bias. Whether it does is a question inspired by signal detection theory. We drew on the framework of signal detection theory to assess bias and sensitivity in hand choice by asking right-handers to choose between two tasks—one performed with the left hand, and one performed with the right. For some participants, the left-hand task stayed constant while the right-hand task was varied. For other participants, the right-hand stayed constant while the left-hand task was varied. We reasoned that if hand preference only reflected bias, participants would choose the generally preferred hand to the same degree, regardless of whether its task was constant or varied. Our participants followed this strategy only to some extent, suggesting that bias and sensitivity both contribute to hand preference.     

Investigations of hemispheric specialization of self-voice recognition

Three experiments investigated functional asymmetries related to self-recognition in the domain of voices. In Experiment 1, participants were asked to identify one of three presented voices (self, familiar or unknown) by responding with either the right or the left-hand. In Experiment 2, participants were presented with auditory morphs between the self-voice and a familiar voice and were asked to perform a forced-choice decision on speaker identity with either the left or the right-hand. In Experiment 3, participants were presented with continua of auditory morphs between self- or a familiar voice and a famous voice, and were asked to stop the presentation either when the voice became "more famous" or "more familiar/self". While these experiments did not reveal an overall hand difference for self-recognition, the last study, with improved design and controls, suggested a right-hemisphere advantage for self-compared to other-voice recognition, similar to that observed in the visual domain for self-faces.     

Alcohol and nicotine intake and prenatal level of androgens measured by digit ratio

The purpose of this study was to examine the associations between using unhealthy substances and the digit ratio (2nd to 4th digit length ratio, 2D:4D) which is supposed to indicate the prenatal testosterone level. The subjects were 455 students, 225 women and 230 men. Participants declared their frequency of smoking and alcohol drinking. There was no significant difference in digit ratios between subjects regularly using both nicotine and alcohol and those who took none of them. When analyzing the two substances separately, there was no relationship between 2D:4D and alcohol drinking, whereas left hand 2D:4D was positively related to smoking only for women (nonsignificant trend was observed for right hand). Contrary to the previous study, our results indicate that there is no relationship between 2D:4D and alcohol drinking. There is, however, a subtle influence of prenatal testosterone levels for cigarette smoking habits in the case of women.     

The relationship between knowing a word and reading it aloud in children’s word reading development

This experiment examined the item-level relationship between 7-year-olds’ ability to read words aloud and their knowledge of the same words in the oral domain. Two types of knowledge were contrasted: familiarity with the phonological form of the word (lexical phonology), measured by auditory lexical decision, and semantic knowledge, measured by a definitions task. Overall, there was a robust relationship between word knowledge and reading aloud success. The association was stronger when words contained irregular spelling-sound correspondences. There was no evidence that a deeper or more semantic knowledge of words was more closely related to reading aloud success beyond the association between reading success and familiarity with the phonological form of the same words. This finding is not compatible with models that see semantics as contributing directly to the reading aloud process, at least during the relatively early stages of reading development. More critical was whether or not a word was considered a lexical item, as indexed by auditory lexical decision performance.     

Unilateral agraphia after section of the posterior half of the truncus of the corpus callosum

Children ranging in age from 3 to 12 tapped on a morse key with their index finger as fast as possible. After a control test, they concurrently tapped and recited a nursery rhyme, recited animal names, and memorized shapes. Previous results suggested that more interference in a motor task results from attempting at the same time to perform another task controlled by the same, than by a different, hemisphere. Right-handed tapping and talking both used left hemisphere space; left-handed tapping and talking were controlled by different hemispheres. Relative to silent tapping concurrent talking caused a greater drop in right-hand tapping rate than in left-hand tapping rate in both the rhyme and animal conditions. Interference by shape memorizing was equal across hands. The differential effect of speaking on right-hand preference indicates the left lateralization of speech output control. The size of this effect did not vary with increasing grade level. The findings support the view that speech output control is fully lateralized at least by age 3 years.     

Hemispheric processing of lexical information in Chinese character recognition and its relationship to reading performance

Hemispheric predominance has been well documented in the visual perception of alphabetic words. However, the hemispheric processing of lexical information in Chinese character recognition and its relationship to reading performance are far from clear. In the divided visual field paradigm, participants were required to judge the orthography, phonology, or semantics of Chinese characters, which were presented randomly in the left or right visual field. The results showed a right visual field/left hemispheric superiority in the phonological judgment task, but no hemispheric advantage in the orthographic or semantic task was found. In addition, reaction times in the right visual field for phonological and semantic tasks were significantly correlated with the reading test score. These results suggest that both hemispheres involved in the orthographic and semantic processing of Chinese characters, and that the left lateralized phonological processing is important for Chinese fluent reading.