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\title{Two-Thirds of Cats Sleep on Their Left Side, Until Somebody Rechecked}
\author{The Science Journaling Club}
\date{Field Notes --- Paper Comparison --- Metascience}

\begin{document}
\maketitle

\begin{abstract}
In June 2025 a thirteen-author team led by Sevim Isparta coded 301 YouTube
videos of sleeping cats and reported, in a two-page item in \textit{Current
Biology}, that \textbf{63.8\%} slept with their left side down --- a
population-level bias framed as an extension of right-hemisphere threat
processing to sleeping posture \cite{isparta2025}. Eight months later, in a
paper posted online in February 2026, Andrew Cooke of the University of
Lincoln ran the same question on three independent platforms and found
nothing distinguishable from chance anywhere: \textbf{51.2\%} left among 123
YouTube cats, \textbf{48.4\%} among 494 on Reddit, \textbf{48.8\%} average
among 60 Instagram accounts \cite{cooke2026}. Between the two papers sits a
formal correction: in October 2025 the original authors removed 107 videos
with documented data-quality problems from their dataset, prompted, Cooke
says, by concerns he had raised --- and the corrected number landed exactly
where it started \cite{isparta2025corr}. This Field Note treats the pair as
one subject. It walks through what a population-level bias actually claims,
why that is not the same statistical object as an individual ``preference''
the way pawedness is \cite{ocklenburg2019,isparta2024}, how three sampling
frames disagree with each other more informatively than any one of them
disagrees with chance, and why a claim, a self-correction and a failed
replication landing inside eleven months is a functioning literature doing
its job rather than a scandal. Every comparative figure below --- pooled
sample sizes, percentage-point gaps, chance expectations --- is the club's
own arithmetic on the two papers' published numbers, marked inline as ours.
\end{abstract}

%============================================================================
\section{Two Papers, Eleven Months Apart}

Most of the papers this club writes up sit alone: one team, one dataset, one
set of conclusions to be checked against the evidence inside that single
paper. This one is different on purpose. The interesting object here is not
either paper by itself, but the eleven months between them and what happened
inside that gap.

Paper one says two out of three cats sleep on their left side and offers a
tidy evolutionary reason why. Paper two, run independently on three different
sources of cat photographs and videos, cannot find that bias anywhere. In
between, the first team quietly fixed a data problem in their own dataset and
got the same answer regardless. None of that makes either paper wrong in some
scandalous sense. It makes them a case study in something worth taking
seriously on its own: a single result, however clean, is a claim waiting for
someone else to try it a different way.

%============================================================================
\section{What the First Paper Actually Measured}

Isparta and twelve colleagues, spanning labs in Turkey, Germany, Italy,
Canada and Switzerland, pulled publicly posted YouTube videos showing a cat
asleep on its side, full body visible from head to hind legs, holding the
position for at least ten seconds \cite{isparta2025}. After screening, 301
videos of 301 different cats went into the final tally: 192 left-side down,
109 right-side down.
\[
  63.8\%\ \text{left}, \quad 36.2\%\ \text{right}, \quad
  \chi^2 = 22.9,\ \mathrm{df}=1,\ p < 0.001.
\]
Not a subtle result, statistically: a departure that size at that sample
size is not what a fair coin produces.

\begin{figure}[htbp]
\centering
\begin{tikzpicture}
\begin{axis}[
  ybar, bar width=28pt, width=11cm, height=6.2cm,
  ymin=0, ymax=220,
  ylabel={cats (of 301)},
  symbolic x coords={Left,Right},
  xtick=data,
  nodes near coords,
  axis lines*=left,
  ymajorgrids, grid style={gray!25},
]
\addplot[fill=claim, draw=claimdeep] coordinates {(Left,192)};
\addplot[fill=nullc, draw=nullc!70!black] coordinates {(Right,109)};
\draw[dashed, gray] (axis cs:Left,150.5) -- (axis cs:Right,150.5)
  node[midway, above, font=\scriptsize, gray] {expected under 50:50 (150.5)};
\end{axis}
\end{tikzpicture}
\caption{The headline result exactly as published: 301 videos, one
observation per cat \cite{isparta2025}. $\chi^2=22.9$, $\mathrm{df}=1$,
$p<0.001$.}
\end{figure}

%============================================================================
\section{The Hemisphere Story, and the Caveat Buried in It}

Isparta and colleagues reach for the logic behind decades of lateralization
research in other species: the vertebrate brain is not symmetric in what its
two halves are good at, and in several species the right hemisphere
specializes in processing threats, giving the left eye and left visual field
a head start on spotting one. Sleep on the left side and the left eye faces
outward into the room rather than into the floor. The leftward sleeping bias
is framed as a sleeping-posture use of that same asymmetry \cite{isparta2025}.

The paper tests the most obvious extension of its own logic and rejects it.
Cats have individual paw preferences the way people have handedness --- a
meta-analysis on which Isparta is a co-author put the fraction of cats with a
measurable left- or right-paw preference at about 78\%
\cite{ocklenburg2019,isparta2024}. If sleeping side and paw preference shared
a cause, left-pawed cats should skew toward one sleeping side and
right-pawed cats toward the other. The authors check this directly:

\begin{quote}
\itshape ``Pawedness could be a further factor that affects sleeping
position. Indeed, about 78\% of cats show either left- or right-sided paw
preferences. But since pawedness in cats displays an individual asymmetry
with about equal numbers of left- and right-pawed cats, our population
asymmetry in sleeping position of 65\% is difficult to explain by paw
preferences.'' \cite{isparta2025}
\end{quote}

Paw preference is individually lateralized --- most cats favor one paw ---
but the population as a whole splits close to 50:50 between lefties and
righties \cite{ocklenburg2019}. There is no population-level pull in one
direction. Sleeping side, as originally reported, is the opposite shape: a
strong population-level pull in one specific direction, cut across
individual cats. That distinction --- population bias versus individual
trait --- is exactly the crack the second paper widens.

%============================================================================
\section{An Erratum Arrived Before Any Rebuttal Did}

Before anyone published a word disputing the result, the original authors
corrected it themselves. In October 2025, \textit{Current Biology} ran a
formal erratum listing specific problems in the original dataset: videos
marked as both included and excluded by mistake, duplicate videos of the
same cat counted more than once, clips shorter than the paper's own
ten-second minimum, one still image miscounted as a video, and clips of a
cat sleeping on a person rather than alone. Fixing all of it meant removing a
combined 107 videos \cite{isparta2025corr}.

Cooke states plainly that he is the reason the correction exists:
``Corrections to the work of Isparta et al.\ (2025) were published in
October 2025 following concerns that I had raised'' \cite{cooke2026}. The
same person who eventually reported a null result had, months earlier,
already pushed hard enough on the original dataset to get a journal
correction issued --- before his own recheck was anywhere near published.

The correction changed nothing about the headline number. After the 107
problem videos came out, the corrected dataset held at 301 cats, 192 left,
109 right --- the same 63.8\%, the same $\chi^2=22.9$, $p<0.001$
\cite{isparta2025corr}.

\begin{table}[htbp]
\centering
\caption{The claim, as it stood after its own correction.}
\begin{tabular}{@{}lll@{}}
\toprule
Quantity & Before the erratum & After the erratum \\
\midrule
Videos analysed & (flawed clips included) & 301 \\
Left-side down & --- & 192 (63.8\%) \\
Right-side down & --- & 109 (36.2\%) \\
Test statistic & --- & $\chi^2=22.9$, $p<0.001$ \\
Videos removed & \multicolumn{2}{l}{107, across five documented error categories \cite{isparta2025corr}} \\
\bottomrule
\end{tabular}
\end{table}

%============================================================================
\section{One Researcher, Three Platforms}

Cooke's recheck does not reanalyse Isparta's videos. It looks for the same
effect independently in three places at once, with explicit, replicable
inclusion criteria: a cat counts as leftward if its left shoulder sits
outside its right shoulder and the curve of its body reads clockwise; a cat
in a neutral or twisted pose does not count; two raters coding the same
footage agreed 99.5\% of the time \cite{cooke2026}.

\begin{itemize}
  \item \textbf{YouTube.} Queried through the YouTube API directly, to avoid
  the recommendation-algorithm and watch-history bias a manual search
  invites, screening 2{,}348 candidate videos down to \textbf{123} unique
  cats.
  \item \textbf{Reddit.} Images from multiple cat-focused subreddits,
  \textbf{494} unique cats in total, with a \textbf{186}-cat subset from
  r/Catbun reported separately.
  \item \textbf{Instagram.} \textbf{60} cat accounts, averaging 29
  sleeping-position images per account --- the one arm built to let the same
  individual be checked more than once.
\end{itemize}

%============================================================================
\section{The Numbers, Side by Side}

None of the three datasets came near the original's departure from chance.
\begin{align*}
  \text{YouTube:}\quad & 63/123\ \text{left} = 51.2\%,\ \chi^2=0.074,\ p=.786 \\
  \text{Reddit (all):}\quad & 239/494\ \text{left} = 48.4\%,\ \chi^2=0.522,\ p=.470 \\
  \text{Reddit (r/Catbun):}\quad & 87/186\ \text{left} = 46.8\%,\ \chi^2=0.774,\ p=.379 \\
  \text{Instagram:}\quad & 48.8\%\ \text{left (SD 11.2 pts)},\ t=0.836,\ p=.407
\end{align*}
\cite{cooke2026}. Every test lands comfortably inside what a coin flip
produces.

\begin{figure}[htbp]
\centering
\begin{tikzpicture}
\begin{axis}[
  width=13cm, height=6.4cm,
  xmin=40, xmax=70, ymin=0.3, ymax=5.7,
  xlabel={percentage coded left-side down},
  ytick={1,2,3,4,5},
  yticklabels={Isparta 2025 ($n{=}301$),Cooke YouTube ($n{=}123$),Cooke Reddit all ($n{=}494$),Cooke r/Catbun ($n{=}186$),Cooke Instagram ($n{=}60$)},
  yticklabel style={font=\scriptsize},
  axis lines*=left,
  xmajorgrids, grid style={gray!20},
]
\draw[dashed, gray, thick] (axis cs:50,0.3) -- (axis cs:50,5.7)
  node[above, font=\scriptsize, gray] {50\% chance};
\addplot[only marks, mark=*, mark size=3pt, color=claim] coordinates {(63.8,5)};
\addplot[only marks, mark=*, mark size=3pt, color=nullc] coordinates {(51.2,4)};
\addplot[only marks, mark=*, mark size=3pt, color=reddit] coordinates {(48.4,3)};
\addplot[only marks, mark=*, mark size=3pt, color=reddit, opacity=0.7] coordinates {(46.8,2)};
\addplot[only marks, mark=*, mark size=3pt, color=insta] coordinates {(48.8,1)};
\end{axis}
\end{tikzpicture}
\caption{All five reported samples, one point each \cite{isparta2025,cooke2026}.
One study sits 13.8 points from chance ($p<0.001$); the other four sit within
3.2 points of it, none significant.}
\end{figure}

Isparta's estimate sits 13.8 percentage points above 50\%; the largest
departure in any of Cooke's three independent samples is the r/Catbun
subset, at 3.2 points --- under a quarter of the original gap
($3.2\div13.8\approx23\%$, our division). Cooke's recheck, across the three
non-overlapping samples, coded 677 cats and accounts in total, more than
double Isparta's 301 ($677\div301\approx2.25\times$, again our arithmetic,
treating r/Catbun as a subset of the Reddit total) \cite{isparta2025,cooke2026}.

Nor is this the first time the exact question came up empty. An earlier
survey of spontaneous feline behaviour by McDowell, Wells and Hepper had
already looked for lateralization in cat sleeping position in 2018 and found
none \cite{mcdowell2018}. Cooke reads his own three-platform null as lining
up with that earlier result rather than overturning a settled consensus ---
it is Isparta's 2025 finding that was the outlier against the prior
literature, not Cooke's recheck of it.

%============================================================================
\section{Even the Outliers Don't Point the Same Way}

The Instagram arm is the one place Cooke could ask a sharper question than
``what is the population average,'' because it holds repeat photographs of
the same 60 individual accounts. A per-account z-score check found only
\textbf{2 of 60} individually left-lateralized and \textbf{4 of 60}
individually right-lateralized \cite{cooke2026}. Six outliers out of sixty,
split almost evenly across both directions rather than clustered leftward
--- close to the count a fair coin flipped repeatedly per account would be
expected to throw up by chance alone at conventional significance
thresholds, our own back-of-envelope check, and certainly not the
leftward-skewed tail a real population bias would predict.

%============================================================================
\section{What ``Preference'' Is Actually Supposed to Mean}

Cooke's sharpest methodological point is not really about sample size:

\begin{quote}
\itshape ``The experimental design has no capacity for the measurement of
individual preference, which typically relies on multiple observations per
individual.'' \cite{cooke2026}
\end{quote}

A paw-preference study watches one cat reach for food dozens of times and
asks whether it favors the same paw consistently enough to call that a trait
of \emph{that} animal \cite{ocklenburg2019,isparta2024}. A single reach tells
you nothing about the animal on its own. Isparta's videos capture each cat
exactly once. Cooke states directly that a population landing at 63.8\% left
is compatible with several different underlying realities --- ``63.8\% of
cats sleeping leftwards every time, all cats sleeping leftwards 63.8\% of
the time or a variation across the population that averages out at 63.8\%''
\cite{cooke2026} --- and a one-shot video cannot distinguish them. It can
only report where the coin landed once, for each of 301 different coins.

%============================================================================
\section{Notes From the Club Table}

\textbf{First disagreement.} Someone argued that four non-significant
results don't disprove one significant one --- absence of evidence is not
evidence of absence, the usual warning. Fair, in general. It matters less
here because the four estimates cluster tightly around 50\% (46.8 to 51.2\%)
rather than scattering around some other shared number. If a real effect
were hiding in the noise, the four independent point estimates ought to at
least lean the same direction; they do not consistently.

\textbf{Second disagreement, not fully resolved.} Isparta's videos and
Cooke's YouTube arm come from the same platform, coded with compatible
definitions, and still land 12.6 percentage points apart (63.8 vs.\ 51.2,
our subtraction). Sampling method has to be doing real work. Isparta does
not publish exactly how the original videos were found; Cooke used the
YouTube API deliberately to route around personal watch-history bias. One
plausible story: a manual search, run from a logged-in account, tends to
surface videos the algorithm already expects that searcher to like, which is
a channel a true population estimate should not have to pass through. We
could not fully settle whether that explains the whole gap, and neither can
Cooke's paper.

\textbf{Standing caution.} We are a school club with no lab and no cats to
film. Everything numerical in this note that is not a direct quantity from
\cite{isparta2025}, \cite{isparta2025corr} or \cite{cooke2026} is the club's
own arithmetic, marked inline.

%============================================================================
\section{Why an Eleven-Month Turnaround Is the Good Outcome}

The original claim went online 23 June 2025. The authors' own correction
went online 4 October 2025, about fifteen weeks later, prompted by the same
person who would go on to publish the recheck. Cooke's independent
three-platform paper went online 24 February 2026 and reached print that
May \cite{isparta2025,isparta2025corr,cooke2026}. Start to finish, claim to
correction to a printed failed replication, the arc spans roughly ten and a
half months (315 days by our count of the calendar) --- comfortably inside a
year, and with the self-correction landing more than four months before the
outside recheck even appeared.

Set this against a larger and more sobering precedent: a 2015 project that
attempted to redo 100 published psychology findings and could only
reproduce a minority of them, a fixture of every conversation about a
so-called replication crisis \cite{osc2015}. What happened with these two
cat papers runs the other way, at a much smaller scale: a specific, numeric,
falsifiable claim; a self-correction of the underlying data within four
months; an independent, multi-platform, methodologically transparent
recheck within eleven. Not every finding gets checked this fast --- sleeping
cats are a more shareable dataset than most psychology stimuli --- but the
process, when it runs, is meant to look exactly like this.

%============================================================================
\section{What Would Actually Settle This}

Not another single-photo dataset, however large. What is missing from every
arm of both papers is a design built from the start to catch individual
consistency: the same cats, photographed sleeping many times over weeks,
with a per-cat leftward proportion computed the way pawedness studies
already compute a per-cat preference index \cite{ocklenburg2019,isparta2024}.
Cooke's Instagram arm gestures at this and found nothing, but 60 accounts
averaging 29 images is a modest start, and Instagram accounts are not a
random sample of cats. A registered, repeated-observation study --- ideally
preregistered, so the analysis plan is fixed before the data arrive --- would
answer the question neither existing paper, for different reasons, can: not
just whether cats as a group lean left, but whether any individual cat
reliably does.

%============================================================================
\section{What We Would Tell Somebody Who Only Read the Headline}

Three things. The original 63.8\% number was real, measured carefully
enough that its own authors could find and fix flaws in the underlying data
without the headline moving. It was also, on the evidence gathered since, an
outlier: three independent samples covering more than twice as many cats
found nothing like it. And the two facts that made this worth a Field Note
are not really about cats --- the people closest to a surprising finding
corrected their own data before anyone forced them to, and an outside check
arrived on a timescale most fields would envy. That is not a story about a
mistake. It is a story about a claim doing exactly what a claim is supposed
to do: sit still long enough for somebody else to check it.

%============================================================================
\begin{thebibliography}{9}

\bibitem{isparta2025}
Isparta, S., Ocklenburg, S., Siniscalchi, M., Goursot, C., Ryan, C.~L.,
Doucette, T.~A., Reinhardt, P.~R., Gosse, R., \c{C}\i{}ld\i{}r, \"{O}.~\c{S}.,
d'Ingeo, S., Freund, N., G\"{u}nt\"{u}rk\"{u}n, O. \& Demirbas, Y.~S. (2025).
Lateralized sleeping positions in domestic cats.
\textit{Current Biology} 35(12), R597--R598. doi:10.1016/j.cub.2025.04.043

\bibitem{isparta2025corr}
Isparta, S., Ocklenburg, S., Siniscalchi, M., Goursot, C., Ryan, C.~L.,
Doucette, T.~A., Reinhardt, P.~R., Gosse, R., \c{C}\i{}ld\i{}r, \"{O}.~\c{S}.,
d'Ingeo, S., Freund, N., G\"{u}nt\"{u}rk\"{u}n, O. \& Demirbas, Y.~S. (2025).
Lateralized sleeping positions in domestic cats [Corrigendum].
\textit{Current Biology} 35(21), 5392--5393. doi:10.1016/j.cub.2025.09.068

\bibitem{cooke2026}
Cooke, A.~S. (2026). No evidence for lateralized bias or preference in the
sleeping positions of domestic cats.
\textit{Laterality: Asymmetries of Body, Brain and Cognition} 31(3),
306--323. doi:10.1080/1357650X.2026.2633997

\bibitem{ocklenburg2019}
Ocklenburg, S., Isparta, S., Peterburs, J. \& Papadatou-Pastou, M. (2019).
Paw preferences in cats and dogs: Meta-analysis.
\textit{Laterality: Asymmetries of Body, Brain and Cognition} 24(6),
647--677. doi:10.1080/1357650X.2019.1578228

\bibitem{isparta2024}
Isparta, S., T\"{o}re-Yarg\i{}n, G., Wagner, S.~C., Mundorf, A., Cinar Kul,
B., Da Gra\c{c}a Pereira, G., G\"{u}nt\"{u}rk\"{u}n, O., Ocklenburg, S.,
Freund, N. \& Demirbas, Y.~S. (2024). Measuring paw preferences in dogs,
cats and rats: Design requirements and innovations in methodology.
\textit{Laterality: Asymmetries of Body, Brain and Cognition} 29(3),
246--282. doi:10.1080/1357650X.2024.2341459

\bibitem{mcdowell2018}
McDowell, L.~J., Wells, D.~L. \& Hepper, P.~G. (2018). Lateralization of
spontaneous behaviours in the domestic cat, \textit{Felis silvestris}.
\textit{Animal Behaviour} 135, 37--43. doi:10.1016/j.anbehav.2017.11.002

\bibitem{osc2015}
Open Science Collaboration (2015). Estimating the reproducibility of
psychological science. \textit{Science} 349(6251), aac4716.
doi:10.1126/science.aac4716

\end{thebibliography}

\end{document}