**5. Results**

The investigation is individual and the answers are put in a separate protocol. Children look consistently at each of the stimuli and name it. All answers are noted regardless of their nature

• wrong answers due to perceptual similarity—perceptively close (for instance instead of

• wrong answers due to association with one element of the image—fragmentary (for

• wrong answers without perceptual similarity—perceptively distant ("kettle"—"chicken,"

The features of the functional system of visual perception are determined by indicators such as accuracy, completeness, volume and time for perception. In our case accuracy of perception is measured by using two parameters: number of correct answers and typology of the

A total of 365 typically developing children without diagnosis of visual disorders took part in the research. All children attend state nursery schools and have Bulgarian as the mother tongue. They form three age groups: 4-year-olds (116 children); 5-year-olds (128 children); and 6-yearolds (121 children). Besides the age factor, the children were separated according to the size of settlement they live in (demographic criterion)—195 children from the capital, 90 living in a big city and 80—in a small town. The proportion according to gender is 173 males and 192 females.

• replacement of the name with a functional description of the object—4 points,

instance instead of "ring"—headphones"; "key"—"path")—2 points,

"pliers"—"scissors" and "spoon"—"shovel")—3 points,

The results are operated with a tri-factor dispersion analysis.

(correct or incorrect). Assessment criteria:

**Figure 4.** Scissors.

30 Prefrontal Cortex

incorrect answers.

• correct naming of an object—5 points,

"elephant"; "scissors"—"spoon")—1 point, • without answer (does not name)—0 points. The values of the F-criteria and the confidence probability (P) indicate that the two independent factors, age (F = 15.75; p < 0.000) and the location (settlement), (F = 4.89; p < 0.008) have a statistically significant impact on the dependent variable for recognizing incomplete images. There is also a significant impact of the paired interaction, Age\*Settlement (F = 3.93; p < 0.003) and Age\*Gender (F = 3.7; p < 0.026).

The profile of the age factor shows a graduate growth in the score for the test, most prominent for the 5-year-olds. The biggest differences are the average scores for children aged 4 and 5 (**Figure 5**), which emphasize the importance of the fifth year for the dynamics of the neuropsychic development.

Duncan's test establishes statistically significant differences between any two means (**Table 1**).

The influence and profile of the demographic factor on the development of the gnosis functions become obvious from the higher summarized score of the children from the big city (**Figure 6**). The average score of the children in the capital is lower, and the lowest is that of children from a small town. There is a statistical significant difference only between the average results of children from a large and a small town. The difference between the average points of children from a big city and capital is close to significance (p = 0.055), and among the children from a capital city and a small town the differences are not credible (**Table 2**).

Attention is paid to the interaction of age and gender factors. The data show identical average scores for girls and boys at 4 years of age, as well as similar ones for children at 5 years of age. Significant gender differences are only recorded in 6-year-olds. Duncan's test demonstrates the influence of both factors through specific differences between pairs of means (**Table 3**).

**Figure 5.** Effect of age factor on the results of recognizing incomplete images.


**Table 1.** Significance of the average scores' differences of the children from each age group.

**6. Discussion**

visual perception.

learning difficulties.

The statistical analysis shows a leading influence on the development of complex forms of non-verbal visual gnosis of age and settlement (demographic) factors. The state of perceptive skills under difficult conditions is characterized by a positive age dynamics and a progressive increase in properly recognized figures. This is confirmed by the results of Duncan's test (**Table 1**) for the presence of meaningful differences between two age groups of children: 4- and 5-year-olds (p ≤ 0.000019), 4- and 6-year-olds (p ≤ 0, 000011) and 5- and 6-year-olds (p ≤ 0.013385). The data support the thesis of improving the right-brain holistic strategy of stimulus processing and the increasing involvement of prefrontal cortex in the processes of

**Ages Gender {1}–32.621 {2}–32.000 {3}–36.649 {4}–37.086 {5}–41.129 {6}–37.750** Girls 0.674 0.006 0.004 0.000 0.001 Boys 0.674 0.002 0.001 0.000 0.000 Girls **0.006 0.002** 0.767 0.004 0.486 Boys **0.004 0.001** 0.767 0.009 0.653 Girls **0.000 0.000 0.004 0.009** 0.022

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**Table 3.** Significance of the average scores' differences of the children of different gender and different ages.

4 years 28% 21% 10% 23% 18% 5 years 36% 21% 13% 17% 13% 6 years 46% 21% 9% 11% 13%

**Table 4.** Distribution of the type of answers for incomplete images for all age group children.

**Ages True answers Perceptively close Fragmented Perceptively distant Without answers**

6 Boys **0.001 0.000** 0.486 0.653 **0.022**

The significant increase in correct responses in children at 5 years shows the particular place of this period in the general neuropsychic development. In terms of visual gnosis, the period is characterized by increasing specialization of the post-central associative regions, improving the performance of the ventral visual system in conditions of deficiency of signs [34, 35] and gradual inclusion of the regulatory mechanisms of the prefrontal cortex. We assume that the age range of 4–6 years can be considered as sensitive for the development of complex perceptive functions and the cases of delay in their formation as prognostic markers for future

The proven influence of the demographic background on the development of non-verbal visual gnosis confirms the thesis of the specific interaction of biological and social factors within the framework of the neuropsychic functioning. Data show the highest average results

**Figure 6.** Effect of settlement factor on the results of recognizing incomplete images.


**Table 2.** Significance of the average scores' differences of the children from the three types of settlements.

Between groups of boys and girls at the age of 4 and 5, credible differences are not observed. The presence of credible differences between those aged 6 years (p ≤ 0.022) is due to the higher mean values than girls.

**Table 4** represents the percentage distribution of the correct answers and of the types of wrong answers (perceptively close, fragmented, perceptively distant and without answers) of the children from each age group. The data allow a more in-depth qualitative analysis of the condition and dynamics of complex forms of non-verbal visual gnosis in children with typical development from pre-school age.

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**Table 3.** Significance of the average scores' differences of the children of different gender and different ages.


**Table 4.** Distribution of the type of answers for incomplete images for all age group children.

#### **6. Discussion**

Between groups of boys and girls at the age of 4 and 5, credible differences are not observed. The presence of credible differences between those aged 6 years (p ≤ 0.022) is due to the higher

**Figure 6.** Effect of settlement factor on the results of recognizing incomplete images.

Small town 0.055564 **0.001722**

**Settlement {1}–36.412 {2}–37.900 {3}–34.263** Capital 0.185263 0.055564 Big city 0.185263 **0.001722**

**Ages {1}–32.313 {2}–36.890 {3}–39.467** 4 years **0.000019 0.000011** 5 years **0.000019 0.013385**

**Table 1.** Significance of the average scores' differences of the children from each age group.

6 years **0.000011 0.013385**

32 Prefrontal Cortex

**Table 2.** Significance of the average scores' differences of the children from the three types of settlements.

**Table 4** represents the percentage distribution of the correct answers and of the types of wrong answers (perceptively close, fragmented, perceptively distant and without answers) of the children from each age group. The data allow a more in-depth qualitative analysis of the condition and dynamics of complex forms of non-verbal visual gnosis in children with typical

mean values than girls.

development from pre-school age.

The statistical analysis shows a leading influence on the development of complex forms of non-verbal visual gnosis of age and settlement (demographic) factors. The state of perceptive skills under difficult conditions is characterized by a positive age dynamics and a progressive increase in properly recognized figures. This is confirmed by the results of Duncan's test (**Table 1**) for the presence of meaningful differences between two age groups of children: 4- and 5-year-olds (p ≤ 0.000019), 4- and 6-year-olds (p ≤ 0, 000011) and 5- and 6-year-olds (p ≤ 0.013385). The data support the thesis of improving the right-brain holistic strategy of stimulus processing and the increasing involvement of prefrontal cortex in the processes of visual perception.

The significant increase in correct responses in children at 5 years shows the particular place of this period in the general neuropsychic development. In terms of visual gnosis, the period is characterized by increasing specialization of the post-central associative regions, improving the performance of the ventral visual system in conditions of deficiency of signs [34, 35] and gradual inclusion of the regulatory mechanisms of the prefrontal cortex. We assume that the age range of 4–6 years can be considered as sensitive for the development of complex perceptive functions and the cases of delay in their formation as prognostic markers for future learning difficulties.

The proven influence of the demographic background on the development of non-verbal visual gnosis confirms the thesis of the specific interaction of biological and social factors within the framework of the neuropsychic functioning. Data show the highest average results for children from a big city, followed by a capital and a small town. According to statistical analysis (**Table 2**), there are significant differences only between the results of children from a big city and a small town (p < 0.001722).

the images, with similar results of perceptively close (21%) and perceptively distant (23%) responses. In 18% of cases, there was a lack of response. The results support the thesis of incomplete functioning of the ventral visual system, hampering the holistic processing of stimuli and underdevelopment of prefrontal areas, resulting in a large number of impulsive

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35

Significantly higher results in children at 5 years confirm the presence of evident age dynamics in the development of gnosis functions. Against the backdrop of an increased proportion of correct recognized figures (36%), the proportion of perceptually distant answers (17%) and lack of response (13%) decreased. Perceptually close responses remain the same (21%). A significant improvement in perceptual abilities is the reason why the fifth year is considered

Similarly to the 5-year-olds, the distribution of the types of responses remains in children at 6 years: the number of faithfully recognized figures (46%) increased and perceptibly reduced distant answers (11%). The ratio of perceptually close errors remains unchanged (21%). The data support the thesis [38] that the transition from 5 to 6 to 6–7 years is a time of intensive maturation of the systems, providing visual information analysis and significant changes in the organization of the neural ensembles in the caudal cortex. Despite the positive changes, the number of faithfully recognized figures in children at 6 years does not exceed half of all answers—a fact that is supported by data [35] of insufficient maturity of the prefrontal cortex and the cortical sections of the visual system (in particular the ventral visual system) during

The summarized results clearly outline the age dynamics of visual perceptions under difficult conditions. If the number of faithful and perceptively distant answers prevails in children at 4 years of age, the number of correct and perceptively close answers prevails over the age of 5 and 6 years. The ratio of responses to perceptual closeness does not change over the three age sub-periods, while perceptibly distant reductions are significantly reduced from 4 to 6 years of age. The results could also be explained by the abovementioned data on the diffused nature

The impact of the demographic factor on the distribution of responses is as follows: in the capital, perceptually distant answers and cases of lack of response are leading; in the big city the perceived errors and lack of responsiveness predominate; in the small town the leading place occupies the replaced by a perceptively close and perceptively distant similarity. Existing analyzes [41] give reason to assume that the mistakes in the capital are mainly due to right-brain difficulties, in the big city, it is the left-brain difficulties, and in the small town, the mistakes are related to both types of difficulties. This is supported by the better functioning of holistic right-hemispheric mechanisms and higher outcomes of children from a big city.

The additionally outlined age norms for the accomplishment of the sample to recognize unfinished images show interesting tendencies of prognostic nature. They are determined by the children's individual results and lead to the separation of three subgroups: leading group, medium group and behind group. Their distribution in the direction of 4- to 5- and 6-year-old children is as follows: leading group: 30–28–27%; medium group: 45–46–47%; and behind group: 25–26–26%. It is noteworthy that the state of subgroups during the

responses.

4–6 years.

critical for neuropsychic development.

of visual perceptual processes before the age of 5.

The interactions of the biological factors, age and gender, have a particular place in the development of complex forms of visual gnosis (**Table 3**). The statistical analysis does not show significant differences in recognizing incomplete images between girls and boys at the age of 4 and 5 years. These are only evident in children at 6 years of age. The observed differences are explained by the higher mean values of the girls—a fact that is indicative оf gender influence on the neuropsychic development of these children. It can be assumed that in girls the ventral visual system and the neural complexes of the prefrontal cortex develop faster, the signs of which become obvious at the end of the pre-school period and explain the better functioning of perceptual and controlling functions.

The qualitative analysis of the results is based on the responses of the children differentiated in several types: correct answers, wrong answers based on perceptive similarities (perceptually close), wrong answers due to one element recognition (fragmentary), wrong answers without perceptive similarities (perceptively distant) or no answers. It is assumed [41] that when recognizing unfinished images, the child must remember the elements and connect them to those memory engrams that contain similar signs. In cases of the complete match between them, the object is recognized correctly. In the case of partial correspondence errors are observed on the basis of close or distant similarity. When the child does not count all, but only the individual signs of the image, the errors are of a fragmentary type. If there is no answer, the reasons are two: missing engrams in memory or an inability to generate an adequate perceptive hypothesis. Errors of perceptual similarity are defined as lighter and fragmented and perceptually distant as heavier.

After a study of a large child population, Ahutina and Pylaeva [41] conclude that perceptually close errors have left-brain mechanisms and are due to weaknesses in the analytical processing of visual information. Fragmented types of wrong answers are explained by right-brain deficits of holistic processing, because on one or two fragments the child draws the conclusion of the whole image. Perceptively distant wrong answers are associated with right-brain or bilateral weakness.

Here are examples illustrating the different types of wrong answers in our survey.

Wrong answers based on perceptual similarity: saber—"knife"; spoon— "shovel," "broom"; water can—"shower"; pliers—"scissors."

Wrong fragmentary-type responses: anchor—"arrow," "hanger"; kettle—"bird," "pig"; needle—"hand," "figure," "pinch."

Perceptively distant wrong answers: sword—"octopus," "spoon," "trunk"; spoon—"man," "rod," "umbrella"; scissors—"magnifying glass," "needle"; ring—"headphones," "banana," "heart," "river."

The quantitative distribution of all responses in the 4–6 years of age period provides valuable information on the ontogenesis of cortical mechanisms in perceptual processing under difficult conditions (**Table 4**). Data show that children at 4 years only recognize truly 28% of the images, with similar results of perceptively close (21%) and perceptively distant (23%) responses. In 18% of cases, there was a lack of response. The results support the thesis of incomplete functioning of the ventral visual system, hampering the holistic processing of stimuli and underdevelopment of prefrontal areas, resulting in a large number of impulsive responses.

for children from a big city, followed by a capital and a small town. According to statistical analysis (**Table 2**), there are significant differences only between the results of children from a

The interactions of the biological factors, age and gender, have a particular place in the development of complex forms of visual gnosis (**Table 3**). The statistical analysis does not show significant differences in recognizing incomplete images between girls and boys at the age of 4 and 5 years. These are only evident in children at 6 years of age. The observed differences are explained by the higher mean values of the girls—a fact that is indicative оf gender influence on the neuropsychic development of these children. It can be assumed that in girls the ventral visual system and the neural complexes of the prefrontal cortex develop faster, the signs of which become obvious at the end of the pre-school period and explain the better functioning

The qualitative analysis of the results is based on the responses of the children differentiated in several types: correct answers, wrong answers based on perceptive similarities (perceptually close), wrong answers due to one element recognition (fragmentary), wrong answers without perceptive similarities (perceptively distant) or no answers. It is assumed [41] that when recognizing unfinished images, the child must remember the elements and connect them to those memory engrams that contain similar signs. In cases of the complete match between them, the object is recognized correctly. In the case of partial correspondence errors are observed on the basis of close or distant similarity. When the child does not count all, but only the individual signs of the image, the errors are of a fragmentary type. If there is no answer, the reasons are two: missing engrams in memory or an inability to generate an adequate perceptive hypothesis. Errors of perceptual similarity are defined as lighter and

After a study of a large child population, Ahutina and Pylaeva [41] conclude that perceptually close errors have left-brain mechanisms and are due to weaknesses in the analytical processing of visual information. Fragmented types of wrong answers are explained by right-brain deficits of holistic processing, because on one or two fragments the child draws the conclusion of the whole image. Perceptively distant wrong answers are associated with right-brain or

Wrong answers based on perceptual similarity: saber—"knife"; spoon— "shovel," "broom";

Wrong fragmentary-type responses: anchor—"arrow," "hanger"; kettle—"bird," "pig";

Perceptively distant wrong answers: sword—"octopus," "spoon," "trunk"; spoon—"man," "rod," "umbrella"; scissors—"magnifying glass," "needle"; ring—"headphones," "banana,"

The quantitative distribution of all responses in the 4–6 years of age period provides valuable information on the ontogenesis of cortical mechanisms in perceptual processing under difficult conditions (**Table 4**). Data show that children at 4 years only recognize truly 28% of

Here are examples illustrating the different types of wrong answers in our survey.

big city and a small town (p < 0.001722).

34 Prefrontal Cortex

of perceptual and controlling functions.

fragmented and perceptually distant as heavier.

water can—"shower"; pliers—"scissors."

needle—"hand," "figure," "pinch."

bilateral weakness.

"heart," "river."

Significantly higher results in children at 5 years confirm the presence of evident age dynamics in the development of gnosis functions. Against the backdrop of an increased proportion of correct recognized figures (36%), the proportion of perceptually distant answers (17%) and lack of response (13%) decreased. Perceptually close responses remain the same (21%). A significant improvement in perceptual abilities is the reason why the fifth year is considered critical for neuropsychic development.

Similarly to the 5-year-olds, the distribution of the types of responses remains in children at 6 years: the number of faithfully recognized figures (46%) increased and perceptibly reduced distant answers (11%). The ratio of perceptually close errors remains unchanged (21%). The data support the thesis [38] that the transition from 5 to 6 to 6–7 years is a time of intensive maturation of the systems, providing visual information analysis and significant changes in the organization of the neural ensembles in the caudal cortex. Despite the positive changes, the number of faithfully recognized figures in children at 6 years does not exceed half of all answers—a fact that is supported by data [35] of insufficient maturity of the prefrontal cortex and the cortical sections of the visual system (in particular the ventral visual system) during 4–6 years.

The summarized results clearly outline the age dynamics of visual perceptions under difficult conditions. If the number of faithful and perceptively distant answers prevails in children at 4 years of age, the number of correct and perceptively close answers prevails over the age of 5 and 6 years. The ratio of responses to perceptual closeness does not change over the three age sub-periods, while perceptibly distant reductions are significantly reduced from 4 to 6 years of age. The results could also be explained by the abovementioned data on the diffused nature of visual perceptual processes before the age of 5.

The impact of the demographic factor on the distribution of responses is as follows: in the capital, perceptually distant answers and cases of lack of response are leading; in the big city the perceived errors and lack of responsiveness predominate; in the small town the leading place occupies the replaced by a perceptively close and perceptively distant similarity. Existing analyzes [41] give reason to assume that the mistakes in the capital are mainly due to right-brain difficulties, in the big city, it is the left-brain difficulties, and in the small town, the mistakes are related to both types of difficulties. This is supported by the better functioning of holistic right-hemispheric mechanisms and higher outcomes of children from a big city.

The additionally outlined age norms for the accomplishment of the sample to recognize unfinished images show interesting tendencies of prognostic nature. They are determined by the children's individual results and lead to the separation of three subgroups: leading group, medium group and behind group. Their distribution in the direction of 4- to 5- and 6-year-old children is as follows: leading group: 30–28–27%; medium group: 45–46–47%; and behind group: 25–26–26%. It is noteworthy that the state of subgroups during the various stages of pre-school age is practically unchanged. We believe that this fact has important prognostic significance and allows an early diagnosis of deficits in complex forms of visual gnosis.

**Author details**

**References**

Neli Cvetanova Vasileva

Address all correspondence to: vasnel@abv.bg

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Sofia University "St. Kliment Ohridski", Sofia, Bulgaria

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Particular attention is paid to the results of the 6-year-old children who are about to go to school. Exported data show that one-fourth of them fall behind a group characterized by the incomplete processing of the right-brain ventral visual system and insufficient involvement of control functions of the prefrontal regions. The engrames of objects in long-term memory are not sufficiently built up, making it difficult to form proper perceptive hypotheses. We assume that children in this group will face obvious difficulties in recognizing and differentiating graphical characters (alphanumeric, numeric and geometric), allowing them to be identified as a risk group for specific learning disorders (dyslexia).

The unsatisfactory development of the complex forms of visual perception could be viewed as a predictor for future reading difficulties and proves the diagnostic and prognostic validity of the sample to recognize incomplete images for the pre-school age period.
