Lateralized Declarative-Like Memory for Conditional Spatial Information in Domestic Chicks (Gallus gallus)

Round 1

Reviewer 1 Report

In this article Loconsole et al show that 5 day old chicks use declarative-like memory system and and it is associated with a left hemisphere dominance.

Overall this is very well written manuscript with a clear hypothesis and methods. Results are interpreted in accordance with observations and statistical outcome. 

I have only one minor suggestion as below;

line 85-96 : move to the start of Methods section 2.2 experimental set up

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The authors investigated declarative-like memory representations in young 5 days old chicks, assessing the roles of the two hemispheres in memory recollection. Therefore, chicks were exposed for three consecutive days to two different arenas (blue/yellow), where they were presented with two panels, each depicting a different stimulus (cross/square). Only one of the two stimuli was rewarded, i.e., it hid a food reward. The position (left/right) of the rewarded stimulus remained constant within the same arena, but it differed between the two arenas (e.g., reward always on the left in the blue context and on the right in the yellow one). At test, both panels depicted the rewarded stimulus, thus chicks had to remember food position depending on the previously experienced contextual rule. Both binocular and right-eye monocular tested chicks correctly located the reward, whereas left-eye monocularly-tested chicks performed at chance level. As a result, the authors showed that declarative-like memory of integrated information is available at early stages of development, and it is associated with a left hemisphere dominance.

The big problem of this study that the results are not really new, because these results corresponds to already published results from Cozzutti, C.; Vallortigara, G. Hemispheric Memories for the Content and Position of Food Caches in the Domestic Chick. Behav. Neurosci. 2001, 115, 305–313, doi:10.1037//0735-7044.115.2.305. The authors should show very exactly, which results are already published and known from the previously study from Cozzutti, C. and Vallortigara (2001) and which results are new and come directly from this study.

Even more, this manuscript needs substantial corrections and improvement and correction before publishing may be possible.

General points:

Please add list of abbreviations to your manuscript.

Please add to your manuscript a video, which show this experiment for each experimental group.

Why you started your experiment at the same time point as Cozzutti, C. and Vallortigara (2001)? What is new in your experiment? Please describe this very exactly in all sections: Introduction, Materials and Methods and especially in the Discussion section.  

Special points:

Keywords: please add also to keywords: Gallus gallus; long-term memory system

Introduction

Lines 32-34: please add references at the end of this sentence.

Lines 34-37: please add more references at the end of this sentence.

Lines 42-44: please add references at the end of this sentence.

Materials and Methods

Lines 114-116: please add also the organization and the exactly date of the permission of your all experiments.

2.2 Experimental setup

Please also describe in this section very exactly both arenas used by you for this experiment. Are they bought? Are they handmade? Produced by? Did you build both arenas according to which scientific study?  

Please answer all this questions and add your answers to this section:

Is this experiment which you did, invented by you or according to another study? Please add the respective references.

How long lasts this experiment for 209 chicks?

How many chicks are located in one arena at the same time?

Where were both arenas? In one room?

Did you get also time for chicks before experiment for adaptation to the experimental room?

2.4 Eye-patching

Lines 158-159: you said: Thirty minutes before testing, the eye of LE and RE chicks was temporary occluded with a removable eye-patch.  

Please describe very exactly these eye-patch. Are they bought? Are they handmade? Produced by?

2.5 Test

Why you started your experiment at the same time point as Cozzutti, C. and Vallortigara (2001)? What is new in your experiment? Please describe this very exactly in all sections: Introduction, Materials and Methods and especially in the Discussion section.  

Lines 189-190: you said: If the chick remained within the non-choice area for the whole duration of the test, its behaviour was scored as absence of choice and the subject was not 190 used in further data analysis.  

Why? This is an important result for statistical analysis. Without this result is not possible to interpret your results exactly.   

2.6 Data analysis

Lines 197-198: you said: The length of time spent by each subject in the choice areas, as well as first choice at test were analysed in R 3.3.3 [21].

Please describe this in this section more exactly.

Results

Lines 217-225: please describe in words, if some statistical significance was found.  Please indicate this also with asterisk accordingly in your Figure 3. Also describe the asterisk values.

Lines 238-242: please describe in words, if some statistical significance was found.  Please indicate this also with asterisk accordingly in your Figure 4. Also describe the asterisk values.

Line 240: you said: .. most of the effects should be interpreted with caution.  Why? Please discuss this very exactly in your Discussion section.  

Lines 254-257: please describe in words, if some statistical significance was found.  Please indicate this also with asterisk accordingly in your Figure 4. Also describe the asterisk values.

Discussion

Very important: The authors should show very exactly, which results are already published and known from the previously study from Cozzutti, C. and Vallortigara (2001) and which results are new and come directly from this study. Please compare very exactly your results with previously already known results. Please add to your Discussion section a Table, which demonstrates your new results opposite already published previously results.   

Legends

Please indicate in all your Figures and Legends the statistical significant results with asterisk and asterisk values.

Figure 3: from your description, the experiment lasts max. 6 min – 360 sec. Why did you show only 300 sec (s)?

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Thank you for your corrections.