Price & Dimensions

Documentation

Introduction

The spatial resolution of a visual system is basically determined by the photoreceptor array in the retina. The central part of the human retina, the fovea, is equipped with densely packed cone photoreceptors, placed with an interval of little more than 2 μm at a distance of about 17 mm from the nodal point of the eye, which thus corresponds to a visual angle of about 0.0084°. However, the cone photoreceptors are not uniform in terms of their spectral sensitivity: they are either short, middle or long wavelength-sensitive. The polymorphic cones form the physiological basis of trichromatic color vision, i.e. the sense of color is produced if cones with different spectral sensitivities are stimulated simultaneously and their signals are processed with so-called spectrally opponent interneurons (Wandell, 1995) at a more central level. Therefore if the visual target is as small as the limit of our spatial resolution, we cannot detect the color of the target (Wandell, 1995).

How small can a visual target be to still allow insects to detect its color? This question has been previously addressed in honeybees and in bumblebees. Honeybees were found to detect objects if their visual angle is larger than 5° (Giurfa et al., 1997; Giurfa et al., 1996), whereas the minimal angle for visual detection was found to be 3° in bumblebees (Spaethe and Chittka, 2003; Spaethe et al., 2001). Color discrimination was lost at larger visual angles, around 15°, thus showing that target detection at smaller angles was achromatic. Here we determined the minimal visual angle at which color detection is possible for the Japanese yellow swallowtail butterfly, Papilio xuthus. This butterfly has ultraviolet (UV), violet (V), blue (B), green (G), red (R) and broad-band (BB) receptors in the retina. These spectral photoreceptors are embedded in fixed combinations in three types of ommatidia. Types I, II and III ommatidia contain four (UV, B, G, R), three (V, G, BB) and two (B, G) classes of spectral photoreceptors, respectively (Arikawa et al., 2003). Papilio butterflies use these receptors to see colors while foraging: they can be trained to approach a paper patch of a certain color by feeding them while they observe the colored stimuli (Kinoshita et al., 1999). The trained butterflies distinguish the training color from a range of different colors as well as from a series of grays. By training butterflies to a colored target, we were able to measure the minimum angular size that a visual target should subtend for the butterflies to detect its color in a Y-maze apparatus.

Apparatus and equipment

The Dog Maze Arena measures 12 m in length and 5.2 m in width with a 10 m long corridor that provides entrance to the arena. The arena consists of long and short corridors. Solid barriers are equipped into some of the corridors to create dead ends. In addition, mesh barriers that allow the subject from seeing the food source but inhibit access are equipped into a couple of other corridors.

Training Protocol

Clean the arena before and after every trial to prevent the influence of any odor cues from previous trials. Appropriately light the apparatus. A tracking and recording system such as the Noldus Ethovision XT can be used to assist with observations.

The following is a sample protocol for the assessment of cognitive bias in dogs using the Dog Maze Arena:

Habituation and Pre-training

Bait the arena with food. Release the subject into the arena and allow it to explore and familiarize itself with the arena. Conduct each habituation session for 5 min a day for 5 days. 

Dog Maze Arena Task

Bait the arena with food. Release the subject into the arena and allow it to find the food rewards within 5 min. Return the subject to the release point and conduct two additional trials. Conduct trials for 3 consecutive days. 

Cognitive Bias Training Trials

Place a rewarded or unrewarded goal box, each consisting of a specific shade of grey, 6 m from the subject. Release the subject and allow it to reach the box within 30 s. Conduct trials until the subjects run faster to the rewarded goal box than the unrewarded goal box. Conduct six consecutive trials with half being rewarded and half unrewarded. 

Cognitive Bias Task

Place one of three probe boxes (each consisting of a separate ambiguous shade of grey) between the two reference shade boxes from training trials. Bait one of the reference shade boxes. Release the subject and allow it to choose a goal box. 

A positive or negative cognitive bias can be evaluated by observing if the subject responds optimistically or pessimistically to the ambiguous stimuli. 

Data Analysis

The following can be observed using the Dog Maze Arena:

• Time taken for the subject to reach the maze entrance from the release point 
• Number of food rewards consumed
• Time taken to consume the food rewards 
• Time taken to complete a trial 

Literature Review

Evaluation of cognitive bias in dogs after spending time on the Dog Maze Arena

Burman et al. (2011) evaluated whether dogs would demonstrate a positive cognitive bias when presented with ambiguous stimuli after undergoing food rewarded trials on the Dog Maze Arena. Twelve female beagles between 11 and 12 months were divided into two treatment groups (neutral and post-consumption) and used in the study. The subjects from the post-consumption treatment group first experienced a rewarding event on the Dog Maze Arena, where they were required to search for food and then perform the cognitive bias task. In contrast, subjects from the neutral treatment group did not undergo Dog Maze Arena trials and were immediately required to perform the cognitive bias task. Results from the arena trials indicated that the subjects were able to find all the food rewards at an average of 3.2 min. During cognitive bias testing, the subjects were trained to reach goal boxes that were 6 m away. The subjects were first presented with either a rewarded or unrewarded goal box that was of two different shades of grey. It was observed that the subjects took significantly longer to reach the unrewarded box. No significant effect of treatment was observed in latency to reach the box. The subjects were then presented with the two reference shade boxes along with either one of three probe boxes (near rewarded, middle, and near unrewarded). Results indicated no significant difference between the two treatments for the near rewarded and near unrewarded probes. However, the subjects took significantly longer to approach the middle probe from the post-consumption treatment group. Overall results indicated that the subjects displayed a negative cognitive bias after the post-consumption treatment. 

Strengths and Limitations

Strengths 

The Dog Maze Arena is a spatial navigation reward-based task. It can be used as a form of enrichment that can induce a positive affective state in the subjects. The corridors of the arena can be equipped with solid barriers as well as mesh barriers to create dead ends and to increase the complexity of the task. It is a non-aversive task and, therefore, does not elicit any form of stress in the subjects. The subjects can easily be trained using the apparatus, and the task can be performed in a short amount of time. The Dog Maze Arena can be used as a pre-requisite to various experimental protocols, such as measuring the cognitive bias of the subjects after experiencing a rewarding event. 

Limitations 

The exploratory behavior of the subjects is highly important in the performance of the task. Unintentional stimuli may interfere with the way the subject performs the task. Factors such as age, gender, and strain of the subjects may affect task performance.

Summary

• The Dog Maze Arena is a rectangular arena that contains long and short corridors as well as solid and mesh barriers that create dead ends. 

• The Dog Maze Arena can be used in various cognitive studies, such as those measuring the affective state of the subjects.

• The Dog Maze Arena can be used as a form of enrichment as well as to improve animal welfare practices. 

• The Dog Maze Arena is non-aversive to the subjects.

References

1. Burman, O., McGowan, R., Mendl, M., Norling, Y., Paul, E., Rehn, T., & Keeling, L. (2011). Using judgement bias to measure positive affective state in dogs. Applied Animal Behaviour Science, 132(3-4), 160–168. doi:10.1016/j.applanim.2011.04.001
2. McGowan, R. T. S., Rehn, T., Norling, Y., & Keeling, L. J. (2013). Positive affect and learning: exploring the “Eureka Effect” in dogs. Animal Cognition, 17(3), 577–587. doi:10.1007/s10071-013-0688-x
3. Verbeek, E., Ferguson, D., Quinquet de Monjour, P., & Lee, C. (2014). Generating positive affective states in sheep: The influence of food rewards and opioid administration. Applied Animal Behaviour Science, 154, 39–47. doi:10.1016/j.applanim.2014.02.011