1. Ecology
  2. Evolutionary Biology
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Positive and negative incentive contrasts lead to relative value perception in ants

  1. Stephanie Wendt  Is a corresponding author
  2. Kim S Strunk
  3. Jürgen Heinze
  4. Andreas Roider
  5. Tomer J Czaczkes
  1. University of Regensburg, Germany
  2. University of Passau, Germany
Research Article
Cite this article as: eLife 2019;8:e45450 doi: 10.7554/eLife.45450
12 figures, 2 videos, 1 data set and 2 additional files

Figures

Experimental Setups.

(A) General setup used for all presented experiments. The 20 cm long runway is connected to the nest box via a 40 cm long drawbridge. The droplet of sucrose solution is placed at the end of the runway (60 cm distance to the nest). (B) Y-maze used on the 10th visit of experiment 2. All arms were 10 cm long. The arm connected to the nest box was covered with unscented paper overlays while the other two arms were covered with lemon and rosemary scented paper overlays (one scent on each side). Visual cues (landmarks) were placed directly behind the two scented arms. The first decision line was located 2.5 cm from the Y-maze centre and marked the initial decision of an ant while the second decision line was located 7.5 cm from the centre and marked the final decision.

https://doi.org/10.7554/eLife.45450.003
Figure 2 with 1 supplement
Food acceptance shown in experiment one for the two training visits (visit 1 and 2) in which ants received one of 12 molarities and the test visit (3) in which all ants received 0.5M (sample sizes: 0.1M: 57; 0.2M: 80; 0.3M: 76; 0.4M: 66; 0.5M: 77; 0.6M: 65; 0.7M: 73; 0.8M: 66; 0.9M: 72; 1M: 55; 1.5M: 72; 2M: 70).

Shown are the mean food acceptance (points) and the 95% confidence intervals (coloured ribbons) for each reference molarity and visit. Data was normalised to show the mean food acceptance of the control group (received 0.5M on each visit) at 0 for all three visits. For a non-normalised graph of the data see Figure 2—figure supplement 1.

https://doi.org/10.7554/eLife.45450.006
Figure 2—source data 1

Experiment 1 – Defining a relative value perception curve; Data Analysis of the Food Acceptance scores for training visits 1 and 2 and test visit 3.

https://doi.org/10.7554/eLife.45450.008
Figure 2—figure supplement 1
Food acceptance shown in experiment one for the two training visits (visit 1 and 2) in which ants received one of 12 molarities (Reference Molarity) and the test visit (3) in which all ants received 0.5M.

Shown are the mean food acceptance (points) and the 95% confidence intervals (coloured ribbons) for each reference molarity and visit. Coloured dashed lines mark the mean food acceptance for ants which received 0.5M (control).

https://doi.org/10.7554/eLife.45450.007
Figure 3 with 1 supplement
Pheromone depositions on the way back to the nest shown in experiment one for the two training visits (visit 1 and 2) in which ants received one of 12 molarities and the test visit (3) in which all ants received 0.5M (sample sizes: 0.1M: 57; 0.2M: 80; 0.3M: 76; 0.4M: 66; 0.5M: 77; 0.6M: 65; 0.7M: 73; 0.8M: 66; 0.9M: 72; 1M: 55; 1.5M: 72; 2M: 70).

Shown are the median number of pheromone depositions (points) and the 95% confidence intervals (coloured ribbons) measured on a 20 cm track right behind the food source for each reference molarity and visit. Data was normalised to show the median number of pheromone depositions of the control group (received 0.5M on each visit) at 0 for all three visits. For a non-normalised graph of the data see Figure 3—figure supplement 1.

https://doi.org/10.7554/eLife.45450.009
Figure 3—source data 1

Experiment 1 – Defining a relative value perception curve; data analysis of the inbound pheromone depositions (to Nest) for training visits 1 and 2 and test visit 3.

https://doi.org/10.7554/eLife.45450.011
Figure 3—figure supplement 1
Pheromone depositions on the way back to the nest shown in experiment 1 for the two training visits (visit 1 and 2) in which ants received one of 12 molarities (Reference Molarity) and the test visit (3) in which all ants received 0.5M.

Shown is the median number of pheromone depositions (points) and the 25/75% quartiles (coloured ribbons) measured on a 20-cm track right behind the food source for each reference molarity and visit. Coloured dashed lines mark the median pheromone depositions for ants which received 0.5M (control).

https://doi.org/10.7554/eLife.45450.010
Figure 4 with 1 supplement
Food acceptance (A and B) and number of pheromone depositions towards the food source (C and D) and towards the nest (E and F) in experiment 2.

The left panels (A, C, E) show behaviour over the eight training trials, in which ants received 0.25M coupled with one scent and 1.5M coupled with another scent on alternating visits. The right panels (B, D, F) show behaviour on the test visit, in which ants always received unscented 0.5M sucrose solution, but the runway leading towards the food source was impregnated with one of the learned scents, causing ants to expect either a high or low reward. 40 ants were induced to expect a high reward, and 32 to expect a low reward. A and B show the mean food acceptance (points) and the 95% confidence intervals (error bars) for each visit; CF show the median number of pheromone depositions on a 20 cm track leading to the food source and the 75%/25% quantiles for each visit.

https://doi.org/10.7554/eLife.45450.012
Figure 4—source data 1

Experiment 2 – ruling out alternative explanations using scent training; data analysis of the food acceptance scores for training visits 1 to 8.

https://doi.org/10.7554/eLife.45450.015
Figure 4—source data 2

Experiment 2 – ruling out alternative explanations using scent training; Data analysis of the food acceptance scores for test visit 9.

https://doi.org/10.7554/eLife.45450.016
Figure 4—source data 3

Experiment 2 – ruling out alternative explanations using scent training; data analysis of the outbound pheromone depositions (to Food) for training visits 1 to 8.

https://doi.org/10.7554/eLife.45450.017
Figure 4—source data 4

Experiment 2 – ruling out alternative explanations using scent training; data analysis of the outbound pheromone depositions (to Food) for test visit 9.

https://doi.org/10.7554/eLife.45450.018
Figure 4—source data 5

Experiment 2 – ruling out alternative explanations using scent training; data analysis of the inbound pheromone depositions (to Nest) for training visits 1 to 8.

https://doi.org/10.7554/eLife.45450.019
Figure 4—source data 6

Experiment 2 – ruling out alternative explanations using scent training; data analysis of the inbound pheromone depositions (to Nest) for test visit 9.

https://doi.org/10.7554/eLife.45450.020
Figure 4—figure supplement 1
Number of food interruptions on the last (9th) visit depending on the ant’s expectations until the crop was filled.
https://doi.org/10.7554/eLife.45450.013
Figure 4—figure supplement 1—source data 1

Experiment 2 – ruling out alternative explanations using scent training; data analysis of the drinking interruption behaviour.

https://doi.org/10.7554/eLife.45450.014
Figure 5 with 1 supplement
Food acceptance shown in experiment 3 for the receivers which received either 0.16, 0.5 or 1.5M through trophallaxis in the nest and then found 0.5M at the end of the runway (sample sizes: 0.16M 63; 0.5M: 52; 1.5M: 53).

Shown are the mean food acceptance (points) and the 95% confidence intervals (error bars) for each reference molarity.

https://doi.org/10.7554/eLife.45450.021
Figure 5—source data 1

Experiment 3 – expectation setting via trophallaxis: the nest as an information hub; data analysis of the food acceptance scores and trophallaxis time in seconds.

https://doi.org/10.7554/eLife.45450.023
Figure 5—figure supplement 1
Food acceptance scores dependent on the trophallaxis time [sec] of receiving foragers for all three reference molarities (each plot represents data for 1 of 3 reference molarities).
https://doi.org/10.7554/eLife.45450.022
Author response image 1
Author response image 2
Author response image 3
Author response image 4
Author response image 5
Number of food interruptions on the last (9th) visit depending on the ant’s expectations until the crop was filled.
Author response image 6
First interruption times [seconds] on the last (9th) visit depending on ant’s expectations for the complete data.
Author response image 7
First interruption times [seconds] on the last (9th) visit depending on ant’s expectations.

Data for ants being confronted with lemon and rosemary odours on the runways were split.

Videos

Video 1
Ant displaying food acceptance score 1.

It shows no food interruptions within the first seconds of feeding.

https://doi.org/10.7554/eLife.45450.004
Video 2
Ant displaying food acceptance score 0.5.

It interrupts feeding within the first seconds of feeding and repeatedly interrupts feeding, but still feeds at the food source (an ant displaying food acceptance score 0 would refuse to feed at the sucrose solution and either return to the nest immediately or fail to fill its crop within 10 min).

https://doi.org/10.7554/eLife.45450.005

Data availability

Raw data has been deposited on Dryad, https://doi.org/10.5061/dryad.77q6s30. Videos of food acceptance scores and other supplementary data such as statistical analyses have been uploaded as online supplementary files.

The following data sets were generated
  1. 1
    Dryad Digital Repository
    1. S Wendt
    2. KS Strunk
    3. JPD Heinze
    4. APD Roider
    5. TJD Czaczkes
    (2019)
    Data from: Positive and negative incentive contrasts lead to relative value perception in ants.
    https://doi.org/10.5061/dryad.77q6s30

Additional files

Supplementary file 1

Sample sizes, mean food acceptance and median pheromone depositions (inward and outward journeys) for the test visits of each experiment and treatment.

https://doi.org/10.7554/eLife.45450.024
Transparent reporting form
https://doi.org/10.7554/eLife.45450.025

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