Effect of Binocular Cues Removal on Skill Abilities

How the removal of binocular cues affects males and females skill ability performance

Abstract:

To test whether skill ability was impaired when binocular cues were removed, participants completed a ‘buzz-wire’ task under three different conditions. Participants completed this task using binocular vision or with vision in their dominant or non-dominant eye only. As well as this, to test the hunter-gatherer hypothesis that females will perform better than males at a the task as it used near-sight vision the sample was divided into males and females. The results found that participants performance was consistently enhanced when they completed the task using binocular vision rather than monocular vision, however there was no significant difference found in performance between genders. The results from this experiment suggest that binocular cues do have an importance in performing skill ability tasks but this performance does not differ between genders.

Introduction:

Numerous research into vision has shown that individuals have binocular cues which allow them to perceive three-dimensional images and judge the distance of objects. Due to the eyes different position on the head each eye perceives an image slightly different in terms of its location, this is known as binocular disparity. Therefore when viewing an object the brain combines information it receives from both eyes, it is this disparity which when converged together allows an individual to recognise depth.

Studies such as Loftus, Servos, Goodale, Mendarozqueta & Mon-Williams (2004) investigated the difference between binocular and monocular vision in various tasks that involved prehension. Their results found that binocular information provides an important role in the position of the hand relative to target, this suggests that binocular vision provides information which helps individuals judge distance.

Research has also found that participants are better at skills that involve movements of the body when they have binocular vision rather than monocular vision. Oliver, Weeks, Lyons, Ricker & Elliott (1998) studied participants ability to catch a ball when using binocular and monocular vision. As expected, participants consistently performed better when they had binocular vision, supporting the theory that binocular vision provides an individual with additional information about distance and depth of objects.

Research has found an advantage in binocular vision in prehension and movement tasks, however the aim of this study is to look at the difference between binocular and monocular vision when participants have to perform a task that involves them using a ‘tool’. A study conducted by Read, Begum, McDonald & Trowbridge (2013) aimed to look at participants performance on task which involves them using tools. Participants completed a standard Morrisby Fine Dexterity Test, a modified Morrisby Test and a ‘buzz wire task’, they completed the task with binocular vision or vision in their left or right eye only. Results found that participants performance was enhanced when they used both of their eyes to complete the task, furthermore, the binocular advantage was greater in tasks that required them to use a tool.

It can be argued that research in to the advantage of binocular vision ignores the differences across genders. Abramov, Gordon, Feldman & Chavarga (2012), found that previous research repeatedly neglects the idea that there may be gender differences in vision. Out of approximately four-hundred studies they found that only a small percentage of studies (23.4%) took in to consideration gender differences within their samples. Many other sensory modalities, such as audition, has found sex differences, suggesting that it is likely that there will also be a difference in vision.

Abramov et al (2012) conducted research that found sex differences in vision; the hunter-gatherer- hypothesis can be used to explain this difference. The hypothesis suggests that due to the different roles males and females had in early hunter-gatherers , males have adapted to be better at far-sight vision whereas females adapted to be better at near-sight vision. This is because in the past males were seen to be the more powerful gender so would take on the role of hunting possible prey, while females gathered food from nearby. It could be argued that this difference in early-hunter gathers resulted in a gender difference in terms of vision.

This study will replicate the ‘buzz wire’ task used in Read et al (2013) study in order to investigate whether participants ability to use tools is impaired when binocular depth cues are removed, as well as looking at gender difference within performance. This will provide advancements on Read et al (2013) and provide further research on the binocular advantage which occurs on tasks that require an individual to use tools. The study expects that overall, participants performance will be enhanced when they have binocular vision rather that monocular vision, moreover, there will be an expectancy for females to perform better than males throughout all tasks.

Method:

Participants:

Forty-one males and forty-three females students were recruited to take part in the experiment. Half of the students took part as a compulsory part of their second year of Psychology, the remaining half were recruited by opportunity sampling.

Apparatus:

A buzz wire task , based on a children’s toy, was used to complete the experiment. This involved a wire (74cm) which travelled across a base (35cm). In order to make the test more challenging the wire was curved and adjusted to construct a three dimensional shape. Participants were provide with glasses which had one side blacked out with tape, the glasses were reversible so the same frame could be used for each condition. The time it took for participants to complete the task was timed manually using a stopwatch.

Design:

This experiment used a within-subjects design which consisted of three levels. There were two dependent variables within this study, how long it takes participants to complete the tasks and the amount of times they came into contact with the wire. The independent variables was whether participants completed the task using binocular vision or with vision in either their dominant or non-dominant eye. The experiment was counterbalanced to avoid extraneous variables, participants were randomly allocated to one out of a possible six orders in which they completed the task.

Procedure:

Participants first had to identify their dominant eye before completing the experiment. To do this the participants had to hold their thumb at arms lengths and align it against a vertical line. They were then told to shut each eye one at a time, the eye which the thumb appeared most aligned with was classed as their ‘dominant eye’.

After identifying the dominant eye the participants were then told which order they had to complete the experiment. Participants then completed the experiment three times, either without the glasses (binocular vision), or wearing the glasses so that their dominant or non-dominant eye was covered (monocular vision). The experiment involved participants guiding the wire loop around the complex track trying to be efficient but accurate. Each time the participant came into contact with the track a buzzing sound occurred, indicating that the participant had made one error.

Results:

Each participant produced a total of six scores, three scores represent how long it took the participant to complete the task (time score) and a score of how many times they came into contact with the wire (buzz score) for each of the three levels. All participants scores where then combined together to produce an average time and buzz score for each of the three levels. These averages are represented in figure 1 and figure 2.

Figure 1: Participants mean and (standard deviation) of how long to complete the buzz wire task in seconds

Figure 2: Participant mean (standard deviation) for the amount of times participant came into contact with wire

A paired samples t-test was conducted to test whether there was a difference between participants performance when using their dominant and non-dominant eye in how long it took them to complete the task. The t-test found no significant difference in how long it took participants to complete the experiment, t (83) = 1.010, p = .316, suggesting that no matter which eye they used it had no effect on how long it took them to complete the task. As there was no difference found, participants times score on the dominant eye and non-dominant eye condition were combined together to produce an overall monocular time score. This times score had a mean (standard deviation) of 40.33 (19.35).

However, a paired samples t-test did find a significant difference between the amount of times participants came into contact with the wire when using their dominant and non-dominant eye, t (83) = 2.313, p = .023., this suggest that participants came into contact with the wire significantly more when using their non-dominant eye rather than their dominant eye.

To test whether participants performance was impaired when binocular depth cues were removed a t-test was conducted between participants buzz score in the binocular condition and their buzz score when using their dominant eye t (83) = 11.580, p < .001, similarly participants had a significantly lower buzz score when using binocular vision rather than just using their non-dominant eye, t (83), 13.183, p < .001. This suggest that removing binocular depth cues worsened participants performance.

A significant difference was also found when comparing participants time score in the monocular and binocular condition, t (83) = 7.069, p < .001. This difference suggests that participants were significantly quicker at completing the task when they had binocular vision.

In order to see how much improvement participants made when using binocular vision rather than monocular vision a ratio was calculated. To do this each condition was divided by one another. The ratios found that in the binocular task participants on average were 1.4 times more quicker at completing the task in the monocular condition. They also made 2.6 times more errors when using their dominant eye rather than both eyes and made 2.9 times more errors when using their non-dominant eye rather than both eyes.

The data file was then divided into males and females in order to test for any gender differences in their performance throughout the study, the means and standard deviation are shown in table 1 and table 2. To test for any significant difference numerous independent t-test were performed. No significant difference was found when comparing males and females time score when they completed the task using only monocular vision, t (82) = .419, p = .676. Similarly, no significant difference was found between genders time score in the binocular condition t (82) = 1.744, p = .085. Suggesting it took males and females the same amount of time to complete the task.

Moreover, there was no gender difference found when comparing participants buzz scores in the binocular condition, t (82) = .961, p = .340, the dominant eye condition t (82) = .280, p = .780 or the non- dominant eye condition t (82) = 1.047, p = .298. From this we can assume that there was no gender difference in performance throughout the entire experiment.

Table 1: Mean and standard deviation on how long it took males and females complete the experiment in seconds with monocular and binocular vision.

Monocular Vision Time Score

Binocular Vision Time Score

Gender

Male Female

Male Female

Mean

41.24 39.47

26.19 26.19

Standard Deviation

19.65 19.24

14.94 10.60

Table 2: Mean and standard deviation of how many times male and female participants came in to contact with the wire in each of the conditions.

Binocular Vision Buzz Score

Dominant Eye Buzz Score

Non Dominant Eye Buzz Score

Gender

Male Female

Male Female

Male Female

Mean

9.80 8.42

23.44 24.19

24.83 27.51

Standard Deviation

7.40 5.76

13.76 10.54

12.63 10.84

Discussion:

As results found that performance was consistently enhanced when using binocular vision rather than monocular vision, it supports the hypothesis that an individual skill ability is impaired when depth cues are removed. This is consistent with Read et al (2013) who also found a greater advantage when using binocular vision in terms of the the number of errors made and the time taken to complete the experiment. Similarly, this experiment found that participants took the same amount of time in completing the experiment, irrespective to whether they used their dominant or non-dominant eye to complete the experiment. However, unlike the results of Read et al (2013) this experiment found a significant difference between participants performance in the non-dominant eye and dominant eye conditions in the amount of times they came into contact with the wire.

This difference found between these experiments could be due to the different methodological measures that were use. Read et al (2013), timed how long the participants wire hoop came into contact with the wire whereas in this experiment the amount of times the participant made the game ‘buzz’ was recorded. Measuring the amount of times the participant made the game ‘buzz’ can be criticised for being subjective. This is because what is classified as one ‘buzz’ can differ between experimenters or across participants. To minimize the subjectivity of this experiment if it was to be replicated it could adopt methods used in the Read et al (2013) study by timing how long the participant stayed in contact with the wire.

Furthermore, where this experiment found that participants were 1.4 times quicker at completing the task when using both eyes rather than one eye, Read et al (2013) found that participants were only 0.3 times faster in their experiment. This suggests that their experiment found a smaller binocular advantage. This difference may be due to the different participants used in these experiments. Read et al (2013) used participants from a large range of ages (seven to eighty-two), whereas this study consisted mainly of young adults. Previous research has found that there may be a difference in brain activity when being shown visual information, Sutija et al (1990), suggesting that there may be a difference in the visual process individuals go through at different ages. If this study was to be replicated on participants from a variety of age groups, it would allow comparison to be made directly between specific ages, providing a more representative sample.

The hunter-gatherer hypothesis proposes that female participants would perform better than male participants in this task as females are arguably better at near-sighted vision. However, results found no significant difference between genders throughout the entire experiment, this is unsupportive on the proposed hypothesis. To test this hypothesis further, an experiment could be conducted which measures males and females performance in tasks which involves recognising a moving object. It would be expected that males would perform better on tasks that involves identifying a moving object. Furthermore, to test the hypothesis, participants performance on a task that involves using far-vision could be tested, again we would expect males to perform better on this task.

It could be argued that no gender difference may have been found within this experiment as a results of males and females adapting to modernised society. Males and females now have similar roles within society and so previous hunter-gatherer roles such as hunting for prey are no longer needed. Furthermore, it can be argued that the sample used in this study (students), would be very familiar with the ‘buzz wire’ game regardless of their gender. Previous exposure to playing this game may have influenced their performance and minimised the gender difference that may have occurred.

This study has provided further evidence and supported previous studies in the idea that binocular vision has an advantage over monocular vision. Furthering the understanding in the way in which vision works helps develop further treatment to those who suffer from visual impairments and allows psychologist to develop measures suitable for testing individuals visual capabilities. Learning the importance of binocular cues not only explain vision but provides further information on the link between what we see and a process of the human brain.

Reference:

Abramov, I. G. (2012). Sex and vision 1: spatiotemporal resolution. Biology of Sex Differences, 3,1-14.

Loftus, A. S.-W. (2004). When two eyes are better than one in prehension: monocular viewing and end-point variance. Experimental Brain Research,3,317-327.

Olivier I, W. D. (1998). Monocular and binocular vision in one-hand ball catching: interocular integration. Journal of Motor Behavior , 10, 343-351.

Read, J. B. (2013). The binocular advantage in visuomoter tasks involving tools. iPerception,4, 101-110.

Sutija V.G, F. A. (1990). Age and binocular advantage: A VEP assessment. Optometry and vision science: official publication of the American Academy of Optometry, 2, 111.