A population of 194 lemurs (Lemur spp.), 116 males and 78 females, from 1 to 30 years of age, was assessed for lateralized hand use in simple food reaching with a minimum of 100 reaches per animal. A hand preference was present in 80% of the population with a bias for use of the left hand that was most characteristic of male lemurs and young lemurs. The results confirm the presence of lateralization in prosimians, and we interpret the sex and age differences in relation to current theories of neural lateralization.

Lateral preferences in food reaching and whole-body turning were assessed in 24 prosimian primates: 16 galagos (Galago moholi) and 8 mouse lemurs (Microcebus murinus). Reach and turn preference in the galago were examined using a single testing procedure; separate procedures were used to evaluate reach and turn preferences in the mouse lemur. The motoric requirements for both species were 1) reach into a Plexiglas container with a single hand for a food item and 2) execution of a whole-body rotation about the long axis of the body. Twenty-three of the subjects tested had a reach preference (15 right, 8 left preferent) and 22 a turn preference (1 right and 21 left preferent). No correlation between the direction of reach and turn preference was found for either species; however an association between right reach preference and female gender was found for the galagos. A species difference in the strength of lateralization was found, with the more bipedal species, the galago, more strongly lateralized in both measures. This result supports the hypothesis that the assumption of upright posture was an important factor in the phylogenetic development of primate lateralization.

Feeding related lateralization was examined in a population of 23 small-eared bushbabies (Otolemur garnettii). The three measures used to determine lateralization were food reaching, holding, and manipulation. Sex and age differences were found, with adult females showing a strong right bias and adult males a left bias. Juvenile males were weakly lateralized and less consistent across measures than adult animals. The use of standard scores to assess lateralization allowed species comparisons to be made. The results of this study were compared with results from a previous study on lateralization in the ring-tailed lemur (Lemur catta). Species comparisons found sex differences to be a stronger factor in lateralization than species differences.

The hand preferences in prey capture and whole-body turning biases after prey capture were assessed in 10 lesser bushbabies (Galago senegalensis) in 8 conditions designed to manipulate posture, visibility of prey and angle of reaching. Each subject received 60 trials in each test condition for a total of 480 trials. Seven subjects had a left-hand preference in food reaching, three right and none were ambipreferent. Eight subjects had a left whole-body turning bias, one right and one had no bias. No correlation was found between reach preference and turning bias. Bipedal posture facilitated the use of the dominant hand, whereas other manipulated conditions did not have a significant effect on hand use. A neuraxial arousal system is postulated as mediator of the bipedal effect on hand use.

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Sex differences in performance of a tactuospatial finger-maze task were assessed in 28 male and 32 female right-handed college undergraduates. The subjects performed the task with their nondominant left hand, and were trained to one error-free trial within specified time limits. Cognitive tests were administered to assess vocabulary, word fluency, and spatial relations capabilities. The results failed to indicate any significant sex differences in performance on the tactuospatial maze in terms of mean errors, number of trials, and trial latencies, or on any of the cognitive tests. The findings strengthen proposals that male superiority in spatial ability may not be as substantial as commonly accepted, and that sex differences in performance may depend on the particular components of spatial ability that are measured in specific tasks.According to some recent reviews (Caplan, MacPherson, & Tobin, 1985;Linn & Peterson, 1985), the reputed male advantage in spatial ability may be limited to some visuospatial tasks . The variety of tasks employed to measure spatial ability has yielded much inconsistent data. For example, both the Porteus Maze Test and the Standardized Road-Map Test of Direction Sense assess visuospatial ability but have produced contradictory and noncorrelated results (Caplan et al., 1985). Similarly, studies that have examined sex differences in performance of different tasks requiring tactuospatial functioning have resulted in inconsistent data : male superiority has been noted in some cases (e.g., Dawson, 1981), but no sex differences or even a female advantage has been found in others (e.g., Biersner, 1980). This study presents additional data regarding sex differences in the performance of a tactuospatial task . MEmODSubjects Twenty-eight male and 32 female right-handed psychology students at Memphis State University participated as subjects for extra credit; the task had been described as involving a manual learning task and some written tests. Test Materials and ApparatusThe Lateral Dominance Questionnaire (Lawson, Goldstein, & Musty, 1975) assesses theperformance of 12 tasks with the dominant hand (8), foot (2), or eye (2). Lateralization of 8 or more items to the right was required for subjects to be classified as right-handed ; these subjects also had identified themselves as right-handed and wrote with the right hand.A plywood finger-maze that measured approximately 27 cm long, 21 cm wide , and 2 ern thick was used to examine tactuospatial performance . One pathway with 5 cul-de-sacs led from start-to goalbox . The pathway and the circular start-and goalboxes were approximately 2 cm and 3 cm wide, respectively .The abbreviated Shipley Vocabulary Test (Shipley, 1967), the Verbal Fluency Test (Thurstone, 1962), and the Spatial Relations subtest of the Differential Aptitude Tests (OAT ; Bennett, Seashore, & WesCorrespondence may be addressed to Jeannette P. Ward, Department of Psychology, Memphis State Univers ity, Memphis, TN 38052 . man, 1974) were employed to assess the subjects' cognitive...

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