Steven D Holladay’s research while affiliated with University of Georgia and other places

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Publications (96)


Mean ± SEM of surgeons' and radiologists' performance for the 3 tests. GVVT: Guay's Visualization of Views Test, MRT: Mental Rotations Test, APMT: Raven's Advanced Progressive Matrices Test.
Comparison of spatial and non-verbal reasoning abilities in veterinarians in the fields of radiology and surgery
  • Article
  • Full-text available

November 2024

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8 Reads

Juan Claudio Gutierrez

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Steven D. Holladay

Spatial ability tests measure capacity for mentally understanding and interpreting three-dimensional images. Such skills have been found to be predictive for anatomical learning success and proficiency in human and veterinary medical students. Veterinarians in the radiology and surgery field develop high levels of three-dimensional topographic anatomic understanding through exposure to anatomy portions of the veterinary curriculum, followed by highly specialized residency programs. Validated testing tools were used to compare spatial and general non-verbal reasoning abilities in veterinarians in the field of radiology (radiology group, RG) and veterinarians in the field of surgery (surgery group, SG). These tests were: Guay’s Visualization of Views Test: Adapted Version (GVVT), the Mental Rotation Test (MRT), and Raven’s Advanced Progressive Matrices Test, short form (APMT). Results showed a significant difference for GVVT scores in favor of the RG (15.2 ± 0.3 and 12.3 ± 0.4, respectively, p < 0.05). There were no significant differences in scores for MRT and APMT between the RG and SG. There was a significant positive correlation between spatial ability tests scores and general non-verbal reasoning test scores for the RG but not for the SG. Future studies are planned to determine if the RG innately possess high spatial and reasoning skills, and to expand the present findings to other veterinary specialty areas.

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Figure 3. Effect of dietary inclusion of 25-hydroxyvitamin D 3 and DL-a tocopherol acetate on average daily feed intake post-Eimeria challenge at wk 25 from 0 to 21 DPI. Starting wk 25, hens grouped in CC, VD, and VE were challenged with sporulated oocysts of 12,500 E. maxima, 12,500 E. tenella, and 62,500 E. acervulina. UC: unchallenged control, PF: pair-fed control, CC: challenged control (12,500 E. maxima; 12,500 E. tenella; 62,500 E. acervulina oocysts per mL), VD: challenged control with inclusion of 5,000 IU of 25-hydroxyvitamin D3 per kg of basal diet; VE: challenged control with inclusion of 100 IU of DL-a tocopherol acetate per kg of basal diet; DPI: days postinoculation.
Figure 4. Effect of dietary inclusion of 25-hydroxyvitamin D 3 and DL-a tocopherol acetate on feed conversion ratio. Starting wk 25, hens grouped in CC, VD, and VE were challenged with sporulated oocysts of 12,500 E. maxima, 12,500 E. tenella, and 62,500 E. acervulina. UC: unchallenged control, PF: pair-fed control, CC: challenged control (12,500 E. maxima; 12,500 E. tenella; 62,500 E. acervulina oocysts per mL), VD: challenged control with inclusion of 5,000 IU of 25-hydroxyvitamin D3 per kg of basal diet; VE: challenged control with inclusion of 100 IU of DL-a tocopherol acetate per kg of basal diet; AOH: age of the hens.
Figure 7. Effect of dietary inclusion of 25-hydroxyvitamin D 3 and DL-a tocopherol acetate on T cell phenotype and white blood cell counts at 14 DPI. Starting wk 25, hens grouped in CC, VD, and VE were challenged with sporulated oocysts of 12,500 E. maxima, 12,500 E. tenella, and 62,500 E. acervulina. UC: unchallenged control, PF: pair-fed control, CC: challenged control (12,500 E. maxima; 12,500 E. tenella; 62,500 E. acervulina oocysts per mL), VD: challenged control with inclusion of 5,000 IU of 25-hydroxyvitamin D3 per kg of basal diet; VE: challenged control with inclusion of 100 IU of DL-a tocopherol acetate per kg of basal diet; DPI: days postinoculation.
Effect of dietary inclusion of 25-hydroxyvitamin D₃ and Vitamin E on performance, gut health, oxidative status, and immune response in laying hens infected with coccidiosis

June 2024

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126 Reads

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1 Citation

Poultry Science

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[...]

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Vitamin D3 (25-hydroxyvitamin D3 (VD)) and vitamin E (VE) have proven to have immunomodulatory and antioxidant functions along with capacities to improve the reproductive function in chickens. Coccidiosis in laying hens at different stages of growth has been shown to negatively affect performance, immune response, and oxidative status, thus increasing the cost of production. A study was conducted to evaluate the influence of dietary VD or VE on performance, gut health, immune response, and oxidative status of laying hens at peak production. Laying hens (23 wk-of-age, n = 225) were randomly allocated into 5 treatment groups (n = 9 hens/replicate) with 5 replicate groups each: 1) unchallenged control (UC), 2) pair-fed control (PF), 3) challenged control (CC), 4) challenged control top-dressed with 5,000 IU of 25-hydroxyvitamin D3 (VD) per kg of diet, and 5) challenged control top-dressed with 100 IU of DL-α-tocopherol (VE). At 25 wk-of-age, hens grouped in CC, VD, and VE were challenged with mixed Eimeria spp. to induce coccidiosis. VD or VE supplemented hens did not impact bird body weight; however, egg production increased by 10.36% and 13.77%, respectively (P < 0.0001). Furthermore, the gut health of the hens was improved with either VD or VE supplementation, as indicated by lowered gut permeability and intestinal lesion scores (P < 0.05). VE significantly reduced the heterophil count (P = 0.0490) alongside numerically increasing the peripheral CD4+ and CD8+ T cells and monocyte counts (P > 0.05). Both VD or VE increased the TAC at 14 DPI compared to UC (P<0.05). Preliminary findings suggest that dietary VD or VE supplementation has the potential to improve gut health, modulate the immune response, and increase egg production in coccidiosis-infected laying hens.


Anatomy of the sternum and humerus in the domestic chicken (Gallus domesticus)

November 2023

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7 Reads

Veterinary Radiology & Ultrasound

Injuries of the sternum and humerus are an important welfare concern in domestic chickens ( Gallus domesticus ), especially laying hens. Published anatomic references using standardized terminology from the Nomina Anatomica Avium ( NAA ) are lacking. Objectives of the current retrospective, descriptive study were to provide a user‐friendly hierarchical table of NAA ‐compliant anatomic terms and labeled images illustrating anatomic structures for the sternum and humerus of domestic chickens. Three‐dimensional model images were downloaded from a publicly accessible platform, labeled in consultation with a veterinary anatomist, and enhanced by a medical illustrator. Findings can serve as a resource for future clinical and research applications.


Antimicrobial and immunomodulatory effects of tannic acid supplementation in broilers infected with Salmonella Typhimurium

August 2022

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95 Reads

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23 Citations

Poultry Science

Infection by Salmonella Typhimurium, a food-borne pathogen, can reduce the poultry production efficiency. The objective of this study was to investigate the effects of tannic acid (TA) supplementation on growth performance, Salmonella colonization, gut barrier integrity, serum endotoxin levels, antioxidant capacity, gut health, and immune function in broilers infected with the Salmonella enterica serovar Typhimurium nalidixic acid resistant strain (STNR). A total of 546 one-day-old broilers were arbitrarily allocated into 6 treatments including 1) Sham-challenged control (SCC; birds fed a basal diet and administrated peptone water); 2) Challenged control (CC; birds fed a basal diet and inoculated with 10⁸ STNR); 3) Tannic acid 0.25 (TA0.25; CC + 0.25 g/kg TA); 4) TA0.5 (CC + 0.5 g/kg TA); 5) TA1 (CC + 1 g/kg TA); and 6) TA2 (CC + 2 g/kg TA). On D 7, supplemental TA linearly reduced STNR colonization in the ceca (P < 0.01), and TA1 and TA2 group had significantly lower reduced STNR colonization in the ceca (P < 0.01). On D 7 to 21, average daily gain tended to be linearly increased by supplemental TA (P = 0.097). The serum endotoxin levels were quadratically decreased by supplemental TA on D 21 (P < 0.05). Supplemental TA quadratically increased ileal villus height (VH; P < 0.05), and the TA0.25 group had higher ileal VH compared to the CC group (P < 0.05). Supplemental TA linearly increased percentage of peripheral blood CD8⁺ T cells on D 18 (P < 0.01). The TA0.5 group had significantly lower lymphocyte numbers compared to the CC groups (P < 0.05). The abundance of monocytes linearly increased with TA supplementation (P < 0.01). Therefore, broilers fed TA had reduced STNR colonization, increased growth performance, decreased serum endotoxin levels, enhanced gut health in the broilers, and stimulated the immune system in broilers infected with STNR. Supplementation of TA (1 to 2 g/kg) enhanced growth performance and gut health via antimicrobial and immunostimulatory effects in broilers infected with STNR.


Working Dog Service, Harmful Agent Exposure and Decontamination

May 2022

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136 Reads

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2 Citations

Working dogs are widely used by service professionals and the military for diverse roles that include sentry, patrol, messenger, tracking, search and rescue, law enforcement, apprehension, as well as explosives and narcotics detection. The expected tasks performed are in many ways determined by the breed, which is customarily a German Shepherd, Dutch Shepherd, Golden Retriever, Border Collie, Labrador Retriever, Beagle, or Belgium Malinois. Working dogs may be subject to injury from dangerous work environments or harmful agent exposure. Personal protective equipment (PPE) has been developed for such dogs, but may impede performance of duties or be poorly tolerated. Canine-specific field-use ready decontamination techniques and kits are therefore needed for use on working dogs that have encountered a harmful agent exposure. This report briefly reviews the development of the military working dog and examines personal protective equipment and decontamination techniques for working dogs after exposure to harmful biologic or chemical agents.


Brief Communication: Predictive Value of Veterinary Student Application Data for Performance in Clinical Year 4

July 2021

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9 Reads

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1 Citation

Journal of Veterinary Medical Education

Student application packages for admission to the University of Georgia College of Veterinary Medicine currently include the following information: undergraduate grade point average (GPA), GPA in science courses, GPA in non-science courses, GPA for the last 45 hours (GPALast45hrs), Graduate Record Examination Quantitative and Verbal Reasoning (GRE-QV) score, GRE Analytical Writing (GRE-AW) score, and grades for 10 required prerequisite courses. From these data, an "academics score" of up to 70 points is calculated. Faculty reviewers also score each applicant up to a maximum of 30 points (FileScore), giving a total possible score of 100 points. Previous analyses demonstrated that the file score and academic variables are significantly related to first-year GPA of veterinary students; however, it is unknown how these variables relate to performance in clinical rotations. The present study pooled the two most recent graduating classes to compare each academic score component to student clinical rotation grades received during year 4 (CGrYr4) in the teaching hospital. Only one component of the student application packages-the pre-admission GRE-QV score-significantly correlated with CGrYr4.


Clinical tolerance of dexamethasone in New Zealand white rabbits

March 2021

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46 Reads

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4 Citations

Research in Veterinary Science

Rabbits have been a popular pet and research species world-wide. In many clinical and research situations, controlling inflammation is necessary for the health of these animals. One of the first drugs commonly employed in veterinary medicine to suppress inflammatory responses is corticosteroids. Unfortunately, steroid use in rabbits is not universally accepted as they are perceived, based on their potent immunosuppressant activity, to negatively impact quality of life. This is may be due, in part, to the lack of well-developed dosing protocols in these animals. This study evaluated the impact of a 5-day IM dexamethasone (Dex, 0.5 mg/kg) protocol on the immunity and clinical health of the New Zealand rabbit. Through two experiments separated by a 10-day washout period, experiment 1 comprised 5-days of dosing with bleedings on day 0, 3, 5 and 7, where experiment 2 consisted of 5-days of dosing with bleedings on day 0, 3 and 5. Animals were monitored twice daily for changes in clinical health. Hematology, T cell subset phenotype, leukocyte cell cycle, histopathology, phagocytosis and oxidative formation were evaluated. Consistent with other species, 5-day dosing with Dex suppressed leukocytes, in particular the T cells (p ≤ 0.003). Interestingly, rabbits failed to show any adverse clinical signs throughout the entire study. This would imply that a 5-day IM Dex (0.5 mg/kg) dosing protocol is well tolerated by New Zealand white rabbits and could be used in rabbits suffering from inflammatory conditions or disease as long as the animal's immune status is closely monitored.


Figure 3. Relationship between RankedAdmScore and PredCR. There was a significant relationship between RankedAdmScore and PredCR (R 2 = 0.46; p < 0.0001). The RankedAdmScore was calculated as described in the test. The derived equation for predicting class rank was PredCR = 709.993 − [(47.328 × GPALast45 hrs) − (1.540 × GRE QV)].
Figure 6. Relationship between PredCR and RankedAdmScore for all three classes collectively. There was a significant relationship between RankedAdmScore and CREY1. This relationship was stronger between CREY1 and PRedCR. The red dashed lines are overlaid upper and lower 95% Individual Prediction Limits (UPL95% and LPL95%). The horizontal gray lines correspond to the 25th and 75th percentiles of the CREY1 values. Their intersections with the UPL95% and the LPL95% (small blue arrows) show the corresponding predicted CREY1 values on the X axis. The derived equation for predicting class rank was PredCR = 709.993 − 47.328 × GPALast45hrs − 1.540 × GRE QV. The RankedAdmScore based on the regression model shows that students on entry with predicted CREY1 scores ≥82 are 95% likely to be in the upper quartile (numerically; poorer students) of the actual CREY1. In like manner, students on entry with predicted CREY1 scores ≤30 are 95% likely to be in the lower quartile (numerically; stronger students) of the actual CREY1.
Variables studied.
Predictive Value of Veterinary Student Application Data for Class Rank at End of Year 1

August 2020

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125 Reads

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8 Citations

Veterinary Sciences

Student applications for admission to the University of Georgia College of Veterinary Medicine include the following information: undergraduate grade point average (GPA), GPA in science courses (GPAScience), GPA for the last 45 credit hours (GPALast45hrs), results for the Graduate Record Examination Quantitative and Verbal Reasoning Measures (GRE-QV), results for the GRE Analytical Writing Measure (GRE-AW), and grades received for 10 required prerequisite courses. In addition, three faculty members independently review and score subjective information in applicants’ files (FileScore). The admissions committee determines a composite Admission Score (AdmScore), which is based on GPA, GPAScience, GPALast45hrs, GRE-QV, GRE-AW, and the FileScore. The AdmScore is generally perceived to be a good predictor of class rank at the end of year 1 (CREY1). However, this has not been verified, nor has it been determined which components of the AdmScore have the strongest correlation with CREY1. The present study therefore compared each component of the AdmScore for correlation with CREY1, for the three classes admitted in 2015, 2016 and 2017 (Class15, Class16, Class17). Results suggest that only a few components of the application file are needed to make strong predictive statements about the academic success of veterinary students during the first year of the curriculum.


Wilcoxon signed rank test results: Mean ± SD of T0, T1, and T2 scores for the three tests from 43 female veterinary medical students.
Improvement of Spatial and Non-verbal General Reasoning Abilities in Female Veterinary Medical Students Over the First 64 Weeks of an Integrated Curriculum

May 2019

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170 Reads

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5 Citations

Spatial visualization ability is defined as the ability to mentally rotate two- and three-dimensional figures. Visual reasoning is the ability to manipulate mental images of an object to reach a certain conclusion and has been linked to spatial ability. There is currently limited information about how entry-level spatial and visual reasoning abilities may be enhanced with progression through the rigorous veterinary medical curriculum. The present study made use of two tests that measure spatial ability and one test that measures non-verbal general reasoning ability in female veterinary students: Guay's Visualization of Views Test, Adapted Version (VVT), Mental Rotations Test (MRT), and Raven's Advanced Progressive Matrices Test, short form (APMT). Tests were given immediately before commencing the integrated veterinary medical curriculum (T0), at week 32 (T1), and at week 64 (T2) into the program. Results showed improved spatial visualization ability as measured by VVT and MRT and improved non-verbal general reasoning ability as measured by APMT at both 32 and 64 weeks. The spatial ability scores measured by VVT and MRT showed a positive correlation with non-verbal general reasoning ability scores (APMT), supporting the idea that these abilities are linked.


Mean ± SEM of female and male performance for the 3 tests of spatial and general reasoning abilities.
Entry-Level Spatial and General Non-verbal Reasoning: Can These Abilities be Used as a Predictor for Anatomy Performance in Veterinary Medical Students?

September 2018

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73 Reads

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4 Citations

There is currently limited available information, but growing interest, in possible relationships between spatial visualization skills in medical students and their academic performance in select areas of the curriculum such as radiographic interpretation and anatomy. There is very limited comparable information on how entry-level spatial visualization skills may correlate with macroscopic anatomy performance in veterinary medical students exposed to an integrated curriculum. The present study made use of a battery of two short tests that measure spatial ability: Guay's visualization of views test (VVT) and mental rotation test (MRT) and, one test that measures general non-verbal reasoning abilities: Raven's Advanced Progressive Matrices Test, short form (APMT). Tests were given to 1st-year veterinary medical students (n = 124) immediately before commencing the integrated veterinary medical curriculum. Results show there is a positive correlation between entry-level spatial ability and non-verbal general reasoning scores confirming these abilities are linked (r: +0.22 and +0.3 for VVT/APMT and MRT/APMT respectively). The dispersion and inconsistency of significant positive correlation between anatomy practical exams grade and spatial and general reasoning scores suggest these abilities either do not correlate with anatomy practical exams grade or, are overcome with progression through the anatomy courses. Males scored higher than females in the spatial ability tests: 16.59 vs. 12.06 for VVT (p = 0.01) and 19.0 vs. 14.68 for MRT (p = 0.01). Scores for APMT did not show a significant difference by gender.


Citations (82)


... This form is responsible for the biological actions of vitamin D, regulating bone and mineral metabolism and modulating immune responses (Fakhoury et al., 2020;Wei et al., 2024). It has been demonstrated that 25(OH)D3 increases the synthesis of nitric oxide, promotes the activity of innate immune cells, modifies adaptive immunity, and produces antimicrobial proteins and inflammatory cytokines in chickens (Shanmugasundaram et al., 2019;Fakhoury et al., 2020;Sharma et al., 2024). Vitamin C, commonly known as L-ascorbic acid, is a water-soluble vitamin that the body converts from glucose. ...

Reference:

Nutritional Aspects for Modulation of Poultry Immune Stimulation
Effect of dietary inclusion of 25-hydroxyvitamin D₃ and Vitamin E on performance, gut health, oxidative status, and immune response in laying hens infected with coccidiosis

Poultry Science

... Moreover, Cihateup duck performance can be enhanced by supplementing the diet with a combination of mangosteen peel flour and turmeric flour [44]. Interestingly, plant extracts rich in diverse polyphenolic compounds have garnered significant attention as alternative antibiotic growth promoters in broiler production [45,46]. Previous studies have demonstrated that xanthones enhance the structure of intestinal villi in broiler chickens, facilitating nutrient absorption and inhibiting the growth of pathogenic bacteria in the intestines [47]. ...

Antimicrobial and immunomodulatory effects of tannic acid supplementation in broilers infected with Salmonella Typhimurium

Poultry Science

... Dogs are participating among many spheres of our life. They are in charge of military service, sentry and patrol, message delivery, tracking, search and rescue, law enforcement, as well as explosives and narcotics detection, work as service dogs for emotional support for veterans and others (Richerson et al., 2023), (Jarrett et al., 2022). People have relied on dogs during the COVID-19 as well, as it caused crises among different aspects of human life (Bao et al., 2020). ...

Working Dog Service, Harmful Agent Exposure and Decontamination

... 9 Current research in veterinary medical education focuses on preadmissions data to inform admissions committees on how to best select applicants who will succeed in completing and graduating the veterinary curriculum, reducing the educational debt to the prospective applicant while decreasing the cost to the institution. 10 Specifically, the limited number of studies assessing preadmission predictors of veterinary academic success has found that undergraduate cumulative GPA, science GPA, 1,2,10,11 the graduate record examination (GRE), [11][12][13] and the demographic variable of age 14 can all directly positively correlate with veterinary school grades. ...

Brief Communication: Predictive Value of Veterinary Student Application Data for Performance in Clinical Year 4
  • Citing Article
  • July 2021

Journal of Veterinary Medical Education

... Whole blood direct smears were made in the field immediately following blood collection and then air-dried. Smears were stained with Wright Giemsa (Sigma-Aldrich, St. Louis, Missouri, USA) by using a 10-min full stain and then a 10-min diluted stain protocol (Mayer et al. 2021). Smears were blindly and independently evaluated by KM. ...

Clinical tolerance of dexamethasone in New Zealand white rabbits
  • Citing Article
  • March 2021

Research in Veterinary Science

... An imbalance between the formation and removal of reactive oxygen species (ROS) and the development of oxidative stress has been widely purported to play an important role in drug toxicity, ischemic damage, neoplastic transformation and metastasis, and cardiovascular, neurodegenerative, and age-associated diseases, 8 as well as in differentiation, development, and aging. 9 Treatment of rodents with cyclosporin during in utero and postnatal development has been reported to result in morphological and functional abnormalities of the thymus and spleen. ...

Developmental Immunotoxicity of Therapeutic Immunosuppressive Drugs
  • Citing Chapter
  • November 2004

... They presented results of prediction using a correlation test that determines the significance of school GPA and SAT as important variables in predicting academic performance. Likewise, Holladay et al. (2020) applied simple and multiple linear regression obtained from 113 students at the College of Veterinary Medicine, University of Georgia from 2015 to 2017 to predict students' first-year performance. Various variables of admission data such as GPA, GPASci (GPA in science courses), GPALast45hr (GPA for the last 45 credit hours), GRE-QV (quantitative and verbal reasoning measures), and GRE-AW (analytical writing measures) were gathered and used for experimentation. ...

Predictive Value of Veterinary Student Application Data for Class Rank at End of Year 1

Veterinary Sciences

... Non-verbal reasoning tests employ a series of perceptual analytical reasoning problems, with each often in the form of a matrix (5). Raven's advanced progressive matrices test, short form, (APMT) is one such matrix-based test used to measure non-verbal reasoning ability (6,7). ...

Improvement of Spatial and Non-verbal General Reasoning Abilities in Female Veterinary Medical Students Over the First 64 Weeks of an Integrated Curriculum

... The difference in terms of gender observed in this study with regard to spatial abilities were also observed in various disciplines including cognitive psychology, [36] veterinary medicine, [37] physiology, [38] and anatomy. [14,19,39,40] The variable of gender is also considered as a significant variable to account for the differences in mental rotation skills. ...

Entry-Level Spatial and General Non-verbal Reasoning: Can These Abilities be Used as a Predictor for Anatomy Performance in Veterinary Medical Students? Spatial and General Reasoning Abilities

... Non-verbal reasoning tests employ a series of perceptual analytical reasoning problems, with each often in the form of a matrix (5). Raven's advanced progressive matrices test, short form, (APMT) is one such matrix-based test used to measure non-verbal reasoning ability (6,7). ...

Entry-Level Spatial and General Non-verbal Reasoning: Can These Abilities be Used as a Predictor for Anatomy Performance in Veterinary Medical Students?