For Wichman and Norman et al. , the detour apparatus consisted of an arena with a starting compartment in the center, across from a holding compartment. The starting compartment consisted of three walls, two opaque and one of wire mesh, so that the holding compartment was visible through the wire mesh. Opposite the wire mesh screen was an opening in the back of the compartment allowing access to the rest of the arena. The holding compartment consisting of a screen so that its contents could be seen by the individual in the starting compartment. The test chick was placed in the central starting compartment and two of its companions from it home pen were placed in the holding compartment. To solve this task, the chicks had to walk away from the familiar chicks, out of the central staring compartment, and around this compartment to reach their companions. Wichman tested ninety 3 day old chicks on a detour test to evaluate their spatial ability. The young chicks had not yet developed perching behavior at the time they were tested. As with the radial arm experiment, all birds were raised in three different rearing environments: control, floor enrichment, and hanging enrichment. The time it took chicks to reach their companions was recorded or, if the chick was unable to successfully complete the task, square pot the trial elapsed at 10 minutes.Forty out of the ninety chicks successfully solved the detour task, however, no relationship was found between onset of perching behavior and the performance of the chicks on the detour test.
This result suggests that the detour test is not a good predictor of early perching behavior in pullets. Additionally, there was no significant effect of rearing environment complexity on the success of chicks in the detour task. Norman et al. also employed a detour task in order to assess if early access to elevated structures affects spatial working memory and route planning in laying hens. They raised chicks from one day of age in either a control or enriched treatment. The control treatment had no elevated structures and the enriched treatment had eight wooden perches arranged in an A-frame structure. In addition to the perches the enriched treatment also had a ramp leading up a platform placed on the second rung of perches. Norman et al tested 48 chicks from both rearing treatments on a detour task at either 14-15 days of age or 28-29 days of age. The test chick was placed in the starting compartment and two of its companions from their home pen were placed in the holding compartment. If the chick left the start box and began walking around the compartment, but then reentered the center of the arena, this was considered an orientation error. Chicks were given a maximum of 5 minutes to complete the task. Out of the 96 birds tested, 67 completed the detour task. There was no significant difference between treatment groups for the number of orientation errors, however the latency to complete the task was significantly shorter for the enriched as compared to the control chicks.
Morris also used a detour task to assess birds from two different rearing treatments on their spatial reasoning . For this study, the unenriched condition included shavings, a hanging feeder, and a nipple line drinker. The enriched treatment included two perches, three live plants for cover, a dust bathing box, two hanging party decorations, and hidden meal worms. At 10 weeks of age 42 birds were tested on a detour task. The target consisted of three familiar birds from their home pen. A barrier was located at the other end of the arena and was made of a mesh screen with an opening on the far-left side, across from the target. The test bird was placed in a starting location behind the barrier and was given 3 to 5 minutes to acclimate in a mesh enclosure. Once the enclosure was lifted, the birds were given 5 minutes to reach their companions. The latency of each test bird to navigate around the barrier and come within 0.5 m of the target was recorded. No significant differences between treatment groups in time taken to reach companions were found. These results contradict the finding from Norman et al. that birds with accesses to vertical structures at a young age did have a shorter latency to complete the detour task than birds without access to vertical structures. It is possible that the difference in these results could be due to the different rearing environments and detour design of these two experiments. The design of the detour task in Morris differed from the design of Norman et al. and Wichman . Instead of the chick walking away from the companion chicks to reach the goal, the Morris design required the chicks to walk towards the companions with them in view at all times through a mesh screen.
The birds were unable to take the most direct route, a diagonal path across the arena, but were not required to walk away from the target at any point to successfully solve the task. Due to this, the Morris detour task does differ from the classic detour task used by Wichman and Norman et al. . However, the inconsistent results between Wichman and Norman et al. should be taken into account when interpreting the impact of rearing environment on performance in a detour task. Due to the varying results across these studies, it is difficult to make definitive conclusions. However, the lack of relationship found by Wichman between early success on the detour task and onset of perching behavior suggests this task may not be relevant to use of vertical space.There is growing evidence in the literature that vertical complexity of the rearing environment of pullets can impact spatial abilities of domestic laying hens. However, tasks such as the hole board test, radial maze, and detour task only test spatial navigation and memory and this is done on a single geometric plane, the ground. Adult hens utilize three dimensional space and therefore their spatial cognitive abilities should also be investigated in relation to depth. While these tasks evaluate spatial memory in hens, a useful skill for finding resources in the aviary, they are not appropriate for assessing visual perception as it relates to navigating around structures in the aviary. In contrast, the jump test does use three-dimensional space and does not directly test spatial memory, making it more relevant to the use of vertical space in commercial aviaries. However, due to the increasing physical difficulty of this test, visual perception and physical skill cannot be separated. There is a great need to study the depth perception of laying hens in relation to complexity of rearing treatment by using both a floor test and a test that utilizes three dimensional space. This methodology would allow for the comparison of performance on both two-dimensional and a three-dimensional test, square plastic plant pots providing greater evidence for the translation of floor tests of spatial cognition to the use of vertical space. It is also important to investigate depth perception as this aspect of spatial cognition has not been specifically evaluated in relation to rearing environment. Adequate perception of depth seems to be vital for gauging the distance to fly or jump between perches and platforms in an aviary. Without proper depth perception, collisions and falls would be likely to occur due to misjudgment of distances.The aim of this study is to gain a better understanding of how rearing environment impacts the cognitive and spatial development of laying hens by examining the development of depth perception. Laying hens reared in three environments of differing vertical complexity were tested on a Y-maze and visual cliff task to evaluate depth perception acuity. Both tasks utilize hens’ motivation to escape after being caught and handled, by offering them the option to exit the experimental apparatuses. Previous studies have used food or social rewards in spatial cognition tasks. In this study, variance in responses due to appetite or sociality was removed by utilizing the hens’ motivation to escape. The Y-maze uses arms of varying lengths to determine if the bird can assess distance and choose the shortest path to escape. The visual cliff was used to evaluate perception of depth as well as method of crossing the visual cliff. In order to account for the disadvantages associated with the traditional visual cliff test, the plexiglass was illuminated and the table was covered with a canopy to reduce reflection.
Additionally, a perch was added in the center of the table, 15 cm above the plexiglass. This prevented tactile information from pecking the glass and the birds’ feet, further concealing the plexiglass. These tests offer greater insight into the topic of spatial cognitive development by examining a previously overlooked, yet relevant aspect of spatial cognition: depth perception.Data Collection At each of three time points a sample of 150 Dekalb White hens were tested . Due to camera malfunctions, video data from three birds were excluded from the visual cliff data set. An equal number of birds were randomly selected from each of three rearing treatments. All birds were tested on the Y-maze task the first week and the visual cliff the second week of testing. Birds were caught from their home pen just prior to testing by corralling them with a metal catch pen. All trials were recorded using a Sony Action Camera and specific behaviors were coded from the video data using Noldus Observer XT . Y-Maze The Y-maze was constructed out of 1 m high wooden boards and included a starting chamber and two arms . The starting chamber was 40 cm long and 60 cm wide, with a guillotine door. The two arms of the maze were 60 cm wide and were joined at a 50o vertex. The arms were adjustable in length so that each arm could be either 30 cm or 90 cm long. The maze was covered by soft, plastic black mesh, preventing the birds from flying out. Both arms were open at the end, allowing the bird the choice to escape into an arena via one of the arms. Chalk lines were drawn where the entrance met each arm of the maze to indicate that the bird had entered an arm of the maze. Additional lines were also drawn at 30 cm from the entrance to mark the point the bird had chosen that side of the maze. Birds were tested with two consecutive trials where the length of each arm varied so that the birds are presented with a 1:3 ratio and a 1:1 ratio .The Y-maze was randomly configured into one of three different orientations: equal length arms or unequal with either the right or left arm being shorter in length. The equal configuration had a 1:1 ratio , while the unequal configuration consisted of a 1:3 ratio . A bird was randomly selected, caught using a catch pen, and assigned an ID number. The bird was then placed into the entrance of the maze facing the vertex of the two arms of the maze. When the bird was placed, a timer was started and the guillotine door of the entrance was closed behind them. If the subject had not exited the maze after two minutes had elapsed, the guillotine door was lifted and then immediately closed to encourage movement of the bird out of the maze. Trials ended after the bird had successfully crossed one of the 30 cm lines or after 2.5 minutes had elapsed. Trials were then repeated once more with the same individual so that each bird was presented with both the equal and the unequal configuration. Time spent in each arm, exit choice, and frequency of flying within or out of maze was recorded . The exit choice was considered correct if, when presented with arms of different lengths, the bird chose the shortest path to the arena . Visual Cliff Two visual cliff tables were used. A small table was used for the 8-week-old pullets while a larger table was used for the 16 and 30-week-old birds . This allowed for the proportions of the table to remain consistent as the birds grew.