Quote from Yurei1453 >>

The issue I see, Pang, is that the rules say you can roll Investigation to figure out clues.

A theoretical such exchange goes like this:

DM: Describes ritual site.
"Investigator": "Investigation roll, 17.  What do I learn?"
DM: "...okay.  Sure.  You notice there's a lot more candles than needed simply to light the spaces, and despite the charring on their wicks there's no sign of any lost or melted wax."
"Investigator": "Cool.  Investigation roll to understand those clues.  19.  What does that mean?"
DM: "Chuck, I don't recall asking for - "
"Investigator": "The rules say I can use Investigation to understand clues.  Please tell me what the clues I discovered mean."
DM: "...Fine.  The candles have burned but there's no melted wax, which means they're magical somehow.  The number and arrangement of candles is indicative of some sort of ritual arrangement."
"Investigator": "Great.  Investigation check to understand that new information better.  Oh cool, 23.  What does this mean?"

So on and so forth, until either the player has tortured the entire plot out of the DM or the DM puts their foot down and tells Chuck to **** off and play the game properly.  Investigation is the only check I know of that is recursive this way - where you can, through a technicality of RAW, roll Investigation to understand the results of your Investigation check.  It is ridiculous, yes.  A lot of DMs will put their foot down early in that process.  Some DMs won't, either because they don't understand the game as well as they need to or because the "investigator" player has an overwhelming personality and can bully their way into doing whatever they like.  In any of those cases, one can just substitute recursive Investigation checks for any sort of actual thinking on the players' part, which reduces the entire game to "roll to see if you win."

I don't want to roll to see if I win.  I want to play, and through that play discover whether or not we win.

 The issue isn't the skill, the issue is that you're letting players have unlimited rerolls.  All you have to do is set limits and not let players just keep rolling until they get a 20.  Most GMs I've heard of do that- you get one roll on an Investigation or Arcana, or History check.  Whatever you get determines how much you achieve, and you can't roll again on that subject until you get a new source of information on the subject.

Quote from Yurei1453 >>

The issue I see, Pang, is that the rules say you can roll Investigation to figure out clues.

A theoretical such exchange goes like this:

DM: Describes ritual site.
"Investigator": "Investigation roll, 17.  What do I learn?"
DM: "...okay.  Sure.  You notice there's a lot more candles than needed simply to light the spaces, and despite the charring on their wicks there's no sign of any lost or melted wax."
"Investigator": "Cool.  Investigation roll to understand those clues.  19.  What does that mean?"
DM: "Chuck, I don't recall asking for - "
"Investigator": "The rules say I can use Investigation to understand clues.  Please tell me what the clues I discovered mean."
DM: "...Fine.  The candles have burned but there's no melted wax, which means they're magical somehow.  The number and arrangement of candles is indicative of some sort of ritual arrangement."
"Investigator": "Great.  Investigation check to understand that new information better.  Oh cool, 23.  What does this mean?"

So on and so forth, until either the player has tortured the entire plot out of the DM or the DM puts their foot down and tells Chuck to **** off and play the game properly.  Investigation is the only check I know of that is recursive this way - where you can, through a technicality of RAW, roll Investigation to understand the results of your Investigation check.  It is ridiculous, yes.  A lot of DMs will put their foot down early in that process.  Some DMs won't, either because they don't understand the game as well as they need to or because the "investigator" player has an overwhelming personality and can bully their way into doing whatever they like.  In any of those cases, one can just substitute recursive Investigation checks for any sort of actual thinking on the players' part, which reduces the entire game to "roll to see if you win."

I don't want to roll to see if I win.  I want to play, and through that play discover whether or not we win.

"I jump across the chasm!" - "Roll Str/Athletics for me." - "27!" - "You don't make it. Take [rolls dice] 35 points of falling damage. You're now prone at the bottom of the chasm."
"I try to figure out what it means that these candles don't burn up!" - "Roll Int/Investigation, please." - "27!" - "You have no idea. These confounding candles are too confounding for you."

So, first off, getting to make a roll doesn't guarantee any results. I know you know that, but it bears repeating since that's one way to skin this cat (figuratively! I love my cat).

"I check out these weird-looking candles, because my spidey sense is tingling and I think they have something to do with that!" - "Roll Int/Investigation, if you will." - "27!" - "There's definitely something strange about them: your trained investigator's eye immediately notices the wax isn't melting, despite the flames looking real and definitely giving off a lot of heat - the room is sweltering. The candles' positions seem peculiar as well - the desk here is deep in shadow, but that barren corner over there is flooded with light and so is that rug that's lying there out of the way." - "Interesting, but that leads to more questions, not to more answers. I'll take a better look at the wax and I'll sniff around that well-lit corner." - "No need to roll, those efforts are part of the Investigation roll you already made. Taking a few extra minutes with the candles and looking over the corner doesn't yield any further insights."

Rerolling is typically not a thing. There's no reason why it should be in this case. That's two ways to handle this, both well within the rules.

Essentially what you are doing is actively encouraging metagaming.  Solving an “investigation check” situation is not something that the players do, it is something their characters do.  Just because the out of game players know the answer doesn’t mean their characters do.  That is why the investigation check is important, the character may know when the player doesn’t or vis versa.  Having only the players solve the situation and that dictating everything the characters know is classic metagaming.  

I'll respond to you more in-depth when I can Pang, but today is super ******* stressful and work is being a *****.  So only a brief note quickly here, while I have a moment.

Hot take: metagaming isn't a problem.  Not a real problem, anyways.  If my players understand the scene I lay out and come to the correct conclusion because of their own cleverness rather than because they chucked dice at my head?  Guess what - those players are going to be thrilled.  They're gonna be smiling, having a great time, congrats all around for their clever thinking.  Or they're going to be horrified, sickened, or dismayed at what their cleverness uncovered.  In either case, their engagement with the game isn't lessened because they accomplished something without consulting the dice.  They're going to be motivated by what they accomplished, instead.

A newbie DM doesn't know what metagaming is.  An average DM complains on the forums about metagaming.  A better-than-average DM makes sure metagaming works for them, not against them.  A master DM metagames right back at the players in service to the game experience.

Was it the Morrow Project that had players actually do some actual IRL physical and mental tests to stat their character's capabilities? 

I just don't see why folks aren't realizing this "problem" as one that's viable only through reductio ad absurdum.  You can "make it a problem" but it I don't think it's really harmed the game over how many years?

To be fair, I don't recall saying that this was a screaming hair-on-fire emergency that was Ruining D&D Forever.  And if I did, sorry.  That was not my intent.  Mostly I was thinking to myself and wondering what other people might think, so I started a thread to discuss.  Discussion is happening, so it's all good.

A good DM can manage/mitigate these issues, as Pang demonstrated.  It's simply a case where the RAW does not help the DM do so, and where surface-level understanding of the game can be a hindrance.  A lot of the common Internet Witticisms and trite, clickbait-y Guru Advice out there is mostly moose piss, and it confuses a lot of issues for players and/or GMs trying to dig deeper into their game.  Honestly, this thread is one of the things that's got me convinced that whenever my turn to run a season comes up in my play group, part of Session 0 will be giving my players an instruction sheet for playing my game.  Tips, advice, and rules for getting the most out of whatever I'm running.

"But Yurei", I hear people protesting already, "everybody knows how to play D&D already!"

Yeah.  We all do.  That doesn't necessarily mean people know how to play my game.  Session 0 is ever more important these days because people are increasingly aware, if often only subconsciously, that "D&D" is an engine, not a game.  The thing you do at your table is the game, and the books everyone is familiar with only facilitates the game.  It doesn't define it.  It's up to the individual GM to finish the half-done, wildly incomplete mess that is D&D 5e for their specific table, and a lot of the "HELP MY GAME IS ON FIRE" threads I see from newer DMs arises from issues of the DM and the players not being on the same page.  This Investigation thing is another facet of the same problem.  I'm fortunate in that players in my group discuss the game as a whole regularly and we all mostly know what everyone else is looking for, but even then, there are hiccups.

Anyways.  @Kotath:
Frankly?  I hate the Six Sacred Scores of D&D.  They're poorly laid out, restrictive, and unhelpful, and if I could replace them with an entirely different system I would.  Sadly, the Six Sacred Scores are one of the most fundamental pieces of what most folks think of when they think "What is D&D?", so we're stuck with them.  but yeah - having three numbers, often randomly generated, that are supposed to 110% dictate to you every last aspect of your character's personality, mannerisms, and capabilities doesn't sit great with me, nah.  It's why I often reduce the impact of mental scores in games I run and/or play in.  They still have an impact, because they must, but I will never say "Sorry Alice, but Blue Tanya is too stupid to understand this conversation.  Please stay quiet and do your best not to contribute."

There are ways to play both high and low scores, even within the annoying strictures of the Sacred Six, that allows a player to contribute.  Both physical scores and mental scores.  Insofar as knowledge scores go?  In my games, the proficiency is more important than the score.  Being trained in something often means you don't need to roll for it, you just get knowledge because that particular knowledge skill is an area of focus for you.  Someone trained in Nature with an Intelligence score of 13, with a +4 total bonus, would get knowledge that an untrained Intelligence 20 character with a raw INT modifier of +5 would not get, because the trained character devoted time, energy, and focus in their past (and the player devoted character building resources) to learning about nature that the savant didn't bother with.  That's how education works, and it's why a low Intelligence character can have smart ideas.  Even a low Wisdom character can have things they do better than others, and a low Charisma character can be confident and assertive within areas they're comfortable in.

Scores are guidelines.  Not ironclad rules.  And they never should've been anything else.

I interpret Investigation as the skill to deduce meaning from clues. I think this is something that lets a character do the thinking instead of the player, but I don't think this is a bad thing. It does require the DM to correctly pace their information exposition, which is tricky, but not impossible. I also don't think that revealing the meanings of things spoils the plot, because I think much of the point of playing is what choices you make from the information given, not whether or not you're going to be given the information. I kind of assume that all the information of a plot is going to be given in the end, with the difference being whether the players are going to confront that information on good footing or not. Super secret information that is never ever given to players is ... dead plot. If it just stays in the DM's head, it doesn't really count, does it?

Personally I don't think of my skill at D&D as my skill to best the challenges, but rather my skill at portraying my character in a fun way to amuse all involved. My character is the one who should be trying to best the challenges and if they fail then they fail, but therein comes the challenge for me as the player, to portray the failure in an amusing way that jives with the character concept.

Quote from Yurei1453 >>

A good DM can manage/mitigate these issues, as Pang demonstrated.  It's simply a case where the RAW does not help the DM do so, and where surface-level understanding of the game can be a hindrance.  A lot of the common Internet Witticisms and trite, clickbait-y Guru Advice out there is mostly moose piss, and it confuses a lot of issues for players and/or GMs trying to dig deeper into their game.  Honestly, this thread is one of the things that's got me convinced that whenever my turn to run a season comes up in my play group, part of Session 0 will be giving my players an instruction sheet for playing my game.  Tips, advice, and rules for getting the most out of whatever I'm running.

Honestly, I don't see this as an issue at all. I brought up the way TSR-era D&D handled this, which is pretty much the polar opposite of the diceapollooza you describe, and that really wasn't so great either. Nothing in the rules requires you to give away the plot or reveal the solution to a puzzle because of an investigation roll. Not even a very high one. In fact, DCs can be entirely irrelevant - you, the DM, can absolutely decide that certain things can't be found out through someone making a roll (that goes for any roll too, including any of the knowledge type rolls that also largely serve to divulge information) and that's absolutely within the rules. What you can do with Investigation at the same time though, is give the players a whiff of the scent of something interesting, useful or valuable - and that's awesome. That's 100% a win for me. Investigation checks let me tell my players that there's something there they want, without telling them what it is or how to get it. It turns the old school situation of the players telling me literally every thing they do in a room to try and find something interesting into a couple of rolls. I get to wax poetically about them going CSI on a room for half a minute to satisfy the theatrical needs of the scene, and then they can get down to the business of figuring out the conundrum with their player brains - not their character dice. If they work it out, great success. If they're having trouble, I can give them a couple of hints. If they're stumped, so be it - they'll do better next time. None of this is bad for the game in any way that I can see. 

Sorry I haven’t had the opportunity to read the whole thread, but a couple things. 

I think investigation is helpful for players playing high INT stat characters. It shouldn’t be an”win” button but a “DM nudges them in the right (or wrong for bad roll) direction” button 

And at our table the DM is the one who asks us to roll investigation or any skill roll. With one exception of a rogue who is mistrustful might ask to roll insight to see if they can tell a person is being truthful. And the DM never says “yes they are lying” it’s more a sense or feeling but never a definite yes or no no matter the roll. 

Other than that players never say I’m rolling investigation or I’m rolling persuasion. It might be the player says “I’m going to look around” or “I’m going to say x, y, or z to see if I can convince the bartender to give some information (or actually role playing it out if the player is comfortable doing so)” and then the DM decides if he wants a roll or not. 

Quote from Yurei1453 >>

So recent discussions, as well as some additional non-DDB reading, have gotten me thinking about the nature of skill checks (more correctly, if less commonly, known as ability checks) and how they influence our games. Most everyone here is (I hope) familiar with the common issue often called “rollplaying”, in which players don’t bother to describe actions or narrate their character’s decisions, but instead say “I make an Arcana check – what does a 17 get me?” Rollplaying is a severe issue and one that can wreck entire campaigns, though fortunately it’s fairly straightforward to train someone out of it.

I was contemplating this problem, as a campaign I’ve just started playing in has an issue with rollplaying and I’m determined to provide a better example...but this got me thinking about skills in general, and one stood out to me as being endemic of rollplaying in general and possibly intrinsically harmful to 5e.

And that is Investigation.

The Investigation skill, to quote the PHB on the matter, is used:
“When you look around for clues and make deductions based on those clues, you make an Intelligence (Investigation) check. You might deduce the location of a hidden object, discern from the appearance of a wound what kind of weapon dealt it, or determine the weakest point in a tunnel that could cause it to collapse. Poring through ancient scrolls in search of a hidden fragment of knowledge might also call for an Intelligence (Investigation) check.”

This seems straightforward enough, a perfectly legitimate use of Intelligence...but the more I thought about it, the less sense it made. Primarily because of one particular sticking point.

All of these are things the player should be doing. Not the character.

The more I pondered this issue, as well as my own Investigation-focused characters, the more I understood why Investigation is often (if erroneously) treated as “careful, hands-on Perception” rather than a knowledge check, and why its uses elsewhere seem so off-kilter.

Let’s assume we have a rogue trained in Investigation who’s searching a mayor’s desk for signs of political corruption. A pretty classic, traditionally accepted case of Investigation. A rollplayer would simply say “Investigation check on the desk, 23. What do I find?”, and would promptly be smacked down by any DM worth their salt. A more typical player might say something like “I rifle through the desk, delicately pulling the drawers open and feeling around inside, looking to see if the dimensions feel off and trying to feel around for hidden catches.”

If a player declared that action to most GMs, the GM would call for an Investigation roll to see if the player found anything. Ho-hum, who cares, typical D&D. But I found myself wondering why. A rules lawyer would say “Um actually, that’s a Perception roll, not an Investigation roll”...and they would be right. The rogue is using their sense of touch to try and discern if anything feels odd or out of place, and using one’s senses to determine if something is odd or out of place is Perception, not Investigation.

So what is Investigation for, in this case? The PHB says it’s for making logical deductions, drawing connections between disparate clues, noticing patterns, or identifying non-obvious information.

All of which are things a good GM tries to get their players to do with their own brains.

Rolling Investigation, by the PHB’s standards of Investigation, is more-or-less equivalent to telling the GM that you’re giving up and would like the GM to give you the answer, provided you shiny math rocks number is big enough. Almost everything the Investigation skill accounts for are the things a player is supposed to be doing themselves, with no more assistance from the GM than a good, solid, consistent description of the scene.

Making logical deductions? That’s for the player to do, not for the GM to do for the player. The player rolling a die and saying “my Knows-Things number is [X], what does that let me know?” is not fun, engaging, or proper roleplaying.

Drawing connections between disparate clues? Again – that’s for the player to do. Rolling a die and saying “Is this number high enough for me to solve the mystery?” is terrible gameplay and makes it almost impossible to conduct any sort of proper mystery games/sessions.

Noticing patterns? Once more – that’s something a GM wants the players to do, not the dice. If the GM is deliberately establishing patterns for their players to pick up on, a player casually throwing a d20 and saying “does this let me know the plot?” is going to incense them. And frankly, if a GM is not deliberately establishing patterns, a player can throw all the dice in the world and get nothing. But if Alice-the-cleric says “Say, have you guys ever noticed...?” and lays out a pattern the GM had no idea they were laying down? Well. That is a super cool moment, and something the GM can absolutely use to better the game.

Virtually the only use of Investigation which does not come at the expense of the players actually playing the game is the somewhat ‘meta’ use of Investigation, i.e. “do I know how to know things?” Casing a city for information on a recent crime wave, spending the day talking to people or pouring over old documents, can be summarized by an Investigation roll since very few players want to go through that tedium. The “identifying non-obvious information” aspect of Investigation, i.e. finding a structural weakness in a wall or locating the one piece of pertinent lore in an entire library, are legitimate uses of Investigation.

But they’re also legitimate uses of other, more useful and interesting proficiencies.

Identifying the weaknesses in a stone wall could be Investigation, sure – but it’s better as an Intelligence (Mason’s Tools) check. You need to know how stone is used to build before you can spot weaknesses. Identifying what weapon might have caused a wound in a body is as much an Intelligence (Medicine) check as it is an Investigation check, or perhaps it’s even an Intelligence (Martial Weapons) check, since knowing weaponry is likely the key factor in being able to know what weapon might have caused a wound. Virtually everything Investigation does could be reclassified as a different proficiency, or a different ability score altogether.

Investigation has, historically, been one of my favorite skill proficiencies. I love being the keen-minded tactician and investigator tasked with doing the Brain Work. But that’s primarily because our table treats Investigation as ‘Slow, Careful, Hands-on Perception’ rather than doing the actual Brain Work, and that’s simply not correct. It’s valid if a table wishes to interpret Investigation that way, but it feels like a disservice in some ways as well. And using Investigation the way the PHB intended it to be used actively gets in the way of playing the game properly. It becomes a “GIMME CLUE” button players can press when they don’t want to put in the work to analyze their information themselves, and with my DM Hat on, I am increasingly unwilling to let players get away with having Lazy Buttons.

What about you guys? What are your thoughts in Investigation, rollplaying, and substituting skill checks for skill?

 No-one actually uses investigation that much in any campaign I have been in, and then only as a kind of "up close passive Perception when you move things".

No-one uses it to magically "know" things.

Also, in defense of arcana, players often leap to insane conclusions (oh, maybe not so insane.  Hi Mr. Mimic) even before rolling.

Quote from Yurei1453>>

Two notes, since there's two distinct threads of conversation happening in this thread.

1.) The skill, as written, states "when you look around for clues and make deductions based on those clues, roll Investigation."  Folks who say that Investigation should not be "Roll to receive plot" are correct - it should not be that thing.  As written, however?  It is that thing.  The skill openly states "roll this when you want to understand clues", and many folks in this thread have openly stated "I shouldn't have to do any thinking - that's what my character is for."  It strikes me as probably being one of the reasons Investigation is so commonly "mis"used as Slow, Careful Perception: DMs intuitively know that having a "Solve the Plot" button on a player's sheet is terrible for their games, and even most players realize this quickly if they don't know it intuitively themselves.  Investigation-as-written basically amounts to letting players spoilerize their own campaign as they play it, which is not okay.  The entire reason people play these games is to find out what happens.  No one would ever play an RPG 'campaign' where the DM said "Okay.  Alice - roll a d20.  This will decide whether the Evil Lich-Monarch subjugates the kingdom in darkness forever, or if your party manages to find a road to victory."  So why should we tolerate people doing that in small scale with Investigation?

The problem isn't the skill, the problem is how people use it or expect it to be used. 

2.) An unintelligent player who puts themself in the shoes of a hyperintelligent character is not going to feel hyperintelligent if their means of Experiencing High Intelligence(C) is throwing a clicky-clack math rock and demanding the DM be smart for them.  Unintelligent players get to have other people be smart for them every day.  I imagine it's awful, and not at all what they want when they create Smartus P. Antalones, their brainiac wizard.  They want to experience for themselves what being the brains of the operation is like, in whatever way they can.  Same with invincibly awkward folks trying to play a suave, rapier-tongued charismatic superstar, or absent-minded oblivious derps trying to play a keenly aware character in perfect tune with their environment and surroundings. 

Faking mental stats by throwing dice at the DM's head and demanding they be smart, charismatic, or wise on the player's behalf does not allow a person to live their fantasy - it allows someone to watch someone else narrate their fantasy for them, which is the next best thing to useless.  It's also patently unfair to the DM, who is being asked to have a  real-life score of 20 in Int, Wis, and Cha so they can perfectly portray all the things everyone is saying it's blatantly unfair to force players to be good at themselves.  "I shouldn't have to be super smart to play a super-smart character!" is a noble goal.  "I should ba able to make the DM be super-smart for me by throwing dice at his head!" is less so, especially when the DM is no more or less likely to have a better IRL stat than any given player.

 I don't think anyone is actually doing that, though. At least not in this thread. And, like many have mentioned before, no-one is advocating that players should be allowed to just roll until they succeed. Instead it has been suggested (by me and many others) that skills like investigation should allow the DM help nudge the players towards the right path to keep the game going.  Exactly how they do that is up to the DM.

Quote from Yurei1453 >>

Two notes, since there's two distinct threads of conversation happening in this thread.

1.) The skill, as written, states "when you look around for clues and make deductions based on those clues, roll Investigation."  Folks who say that Investigation should not be "Roll to receive plot" are correct - it should not be that thing.  As written, however?  It is that thing.  The skill openly states "roll this when you want to understand clues", and many folks in this thread have openly stated "I shouldn't have to do any thinking - that's what my character is for."  It strikes me as probably being one of the reasons Investigation is so commonly "mis"used as Slow, Careful Perception: DMs intuitively know that having a "Solve the Plot" button on a player's sheet is terrible for their games, and even most players realize this quickly if they don't know it intuitively themselves.  Investigation-as-written basically amounts to letting players spoilerize their own campaign as they play it, which is not okay.  The entire reason people play these games is to find out what happens.  No one would ever play an RPG 'campaign' where the DM said "Okay.  Alice - roll a d20.  This will decide whether the Evil Lich-Monarch subjugates the kingdom in darkness forever, or if your party manages to find a road to victory."  So why should we tolerate people doing that in small scale with Investigation?

Related, but more into part two...

2.) An unintelligent player who puts themself in the shoes of a hyperintelligent character is not going to feel hyperintelligent if their means of Experiencing High Intelligence(C) is throwing a clicky-clack math rock and demanding the DM be smart for them.  Unintelligent players get to have other people be smart for them every day.  I imagine it's awful, and not at all what they want when they create Smartus P. Antalones, their brainiac wizard.  They want to experience for themselves what being the brains of the operation is like, in whatever way they can.  Same with invincibly awkward folks trying to play a suave, rapier-tongued charismatic superstar, or absent-minded oblivious derps trying to play a keenly aware character in perfect tune with their environment and surroundings. 

Faking mental stats by throwing dice at the DM's head and demanding they be smart, charismatic, or wise on the player's behalf does not allow a person to live their fantasy - it allows someone to watch someone else narrate their fantasy for them, which is the next best thing to useless.  It's also patently unfair to the DM, who is being asked to have a  real-life score of 20 in Int, Wis, and Cha so they can perfectly portray all the things everyone is saying it's blatantly unfair to force players to be good at themselves.  "I shouldn't have to be super smart to play a super-smart character!" is a noble goal.  "I should ba able to make the DM be super-smart for me by throwing dice at his head!" is less so, especially when the DM is no more or less likely to have a better IRL stat than any given player.

The truth of the matter is that there is no single person on the entire Earth who can successfully "pretend to be someone else" to the extent people demand of their roleplaying.  All of your decisions come from your brain, are colored by your knowledge and experiences, and are determined by your mental capabilities.  When Alice steps into the shoes of Blue Tanya, Muscle Queen of the Wastelands, she is not "making the decisions Blue Tanya would make".  She is making the decisions Alice-the-player would make if she were isekai'd into the role of Blue Tanya.  Telling Alice she is not allowed to use her own brain to run Blue Tanya is ridiculous, but that's what people so often suggest.  The common refrain of "someone with a really high IRL mental stat shouldn't be allowed to use that as their dump stat and then be super good at it anyways!  That's not fair!" is true but also useless, because that is unavoidable.  

You cannot ignore a player's ability to play the game, any more than you can ignore the character's abilities within the game world.  Alice's basic high school education grants her a degree of knowledge Blue Tanya the low-intelligence barbarian would never have access to.  Alice cannot turn that knowledge off.  She cannot not know what she knows.  She can attempt to refrain from using that knowledge, but her decisions will always be influenced by what she knows.  Blue Tanya does not have her own brain - Alice has a Blue Tanya filter in her Alice brain she clicks on whenever it's game time.  If Alice is not allowed to make the decisions Alice would make because "it's not fair", and instead is forced to throw dice any time Blue Tanya has to do anything more complicated than relieve herself, Alice will not enjoy the game.  She has to be allowed to let her own Alice-talents shine, which may well mean Blue Tanya is smarter than she should be.

That is simply the reality of the game.  Alice cannot not be Alice.  I cannot not be me, however much certain folks around here would love that.  You cannot not be you.  That means there will always be limits on what you can successfully portray.  The further beyond those limits you go, the more you rely on the dice to do your gaming for you, the more you abstract and fuzz and obscure because you can't back up your sheet?  The less satisfying your game will be.  That's not any sort of judgment on people or the game, it's merely an observation of fact.  Boiling away everything but "I throw a d20 to see if I win or lose" also means you've boiled away everything that makes this sort of game amazing.  You have overcooked spaghetti, not a splendid campaign.

Don't overcook your spaghetti.

 Well, I can just say that I fully disagree with you here. You can narrate your own character and still roll mental stat dice just fine without it breaking the narrative, immersion or roleplay.

Skipping a lot of posts to write this, but the troublesome application of investigation is for the case the player is not as smart as the character-- or as a safety net for a player who just isn't coming to the right conclusions and needs a clue to get them back on track. Nothing wrong with that. If anything is overpowered, it's most likely due to mismanagement by the GM.

I dont think there's anything wrong with investigation, it can have overlap sure but a lot of skills can have overlap depending on what is being attempted.  I think the issue really lies in as you said roll-playing.  Even a simple statement of "I check the desk over for anything" is good enough to prompt an investigation roll that might find a hidden compartment in my book, but simply saying "I roll investigation, 24" really isn't..  its up to the DM to ask for the roll not the player.

But again saying careful perception check is a lot like athletics/acrobatics,  its more about how you say your doing something like.. I do a running jump to cross the pit vs I do a backflip over the pit.   "I rummage through the desk" could be investigation vs "I look around the room for something out of the ordinary" being perception

For me , there are certain ways that I look at skills and proficiencies when I am DMing. For investigation vs percept, I know what the rules say how they are supposed to be used, but I will often interchange them. Perception is supposed to be tied to senses, but Wisdom is a poor ability for that. If I have a character with low wisdom (and I do), he is played as having poor self awareness. He is vain and often doesn’t understand how he comes across to others. As the PHB says: “

Wisdom reflects how attuned you are to the world around you and represents perceptiveness and intuition.

Wisdom Checks

A Wisdom check might reflect an effort to read body language, understand someone’s feelings, notice things about the environment, or care for an injured person.  

Someone who doesn’t pick up on body language or feelings doesn’t suddenly have poor eyesight or sense of touch or are too stupid to look for secret latches in a desk drawer. Depending on the situation I will allow a player to use either perception or investigation to find hidden things because both perceptiveness and investigative skills can help. 

Skill Check spamming has been brought up. While you can just disallow this, one way to overcome it is to adjust the DC level. A wizard with proficiency in Arcana might have to defeat a DC of 15, but a barbarian with no proficiency or background in magic might need a 20 or even 25. 

the problem of rollplaying VS roleplaying (which seem to be the main point of your argument here) is that I am not my character and my character is not me. My character knows thing that I don't know and I know thing that my character do not. So yes "rollplaying" is very important if you want to respect both the player and the character.

Me Benoit in the real life. I have been doing puzzles and riddles all my life, So if you the DM hand me (Benoit) a puzzle in real life and tell me to resolve it and if I succeed to resolve it, we consider that my character in game also resolve it... well seem weird that my 8 Intellect barbarian who would probably smash that puzzle after 3 seconds, is able to resolve it...
So yes asking my barbarian to do an investigation roll to see if he can resolve the puzzle, then when he will roll his 10-1 get mad and smash it make more sense to me then asking me a nerd who love puzzle to resolve it.

Similar thing about my rogue searching the desk for a secret compartment containing secret documents that could be use to blackmail the mayor.
Me Benoit in real life, I never had a trap desk with secret compartment etc... yes I can imagine how a fake bottom work and can imagine that sure if from the outside the drawer seem to be 8 inch deep but inside it's only 4 inch deep, there is probably a fake bottom. But me Benoit have no idea about catches, and latches etc... so me Benoit would probable miss them in real life and me Benoit won't think about asking for something I do not know about. (the same way that if I ask you to describe to me how your ranger would pick mushroom that are safe to eat VS mushroom that are poisonous... even if you are a mycologist in real life you have no idea about the mushroom in my homebrew world. so you are unable to tell me you pick the white mushroom with blue dots, but avoid the green mushroom with purple square. But your ranger with expertise in survival should know it even if you do not. The best you can do is you are foraging for safe to eat food, but as a DM unless you tell me otherwise, I will consider by default that you are searching for safe to eat food.
The same courtesy should be shown to my rogue. Even if me Benoit have no idea how to search a desk, but my rogue, expert in perception and in investigation, with 14 wisdom and 12 intellect, who all his life trained in searching for secret compartment in various type of desk, dresser wall etc... he should know about those catches and latches, without e having to explain every detail about how to do a search

If the player playing the barbarian tell you he rolled a 24 to lift the heavy portcullis, do you give him 5 damages because he didn't specified he took the proper squatting position, making sure his back was straight in order to lift with his leg? or you just accept that the barbarian trained in athletic know how to lift a portcullis without injuring himself?

Do you expect the player playing the rogue forging a document to actually forge a document?

I am a nerd, I am shy, I am introverted, I hate public speaking and I'm not a great orator, I guess Apollo spited in my mouth as well, just like Cassandra. I am unable to write and even less speak a convincing speech that will rouse the moral and make people listen to my advice, even if those advices are simple, beneficial and proven to work.
But my Bard, with expertise in persuasion, with the silver tongue feature (all roll of 9 or less on a persuasion check is consider like a 10+my bonuses) with my 22 charisma is a master orator, he should easily convince the guard that we are the rat extermination crew and he should let use pass even if we lost the paper or the king will have his head if he learn that he prevented us from doing our job and a his VIP guess found a rat in his soup...
But do not ask me Benoit to tell you the speech. I failed at convincing the security guard at my work to let me pass and I had my security badge with me, but somehow it was demagnetized, I had to wait 1 hours for his supervisor to call my supervisor to confirm that yes I am working in the building and should be allowed in and that they'll fix my card.
So yes I will tell you" My bard will convince the guard that we are the rat extermination crew, we lost the paper, but it was a clerk named Sebastien who signed it, and he insisted that we do the job this morning, because there is an important diner tonight with VIP and the king himself requested that all rat be exterminate" then ask you if name dropping the name of the clerk or the king himself wanting requesting it give me advantage or something then roll my persuasion check.

It's a roleplaying game. I'm roleplaying a character that isn't me. My character can do stuff that I don't even know how to do them, even less how to do them efficiently and properly.
When my barbarian need to lift a heavy object no DM ever asked me to lift that object in real life or explain the proper position required to lift that object to avoid injuring. I just roll athletic. If I tell him that I'm using a lever I might get advantage on my roll.
When my wizard examine a magical sword to figure how to activate it, I do not need to explain how the magical leyline of his world entertwine with the metal of the sword and how to decipher the magical rune on the pummel. I simply say: My wizard examine the sword and try to figure out how it works, roll 23 on Arcana. And the DM tell me that I find some rune on the pummel with the arcanic word for "fire" and when I pronounce it the blade erupt in fire, congrats you found a fame tongue sword.
When my sorcerer try to convince the marchand to give us a discount, I do not need to tell my speech word for word. I simply say "I want to convince the marchand to give us a discount" if I add some reasons "we are mandated by the king to save this town, here the decree signed by the king" or "we will buy exclusively from you" or  that he could be the blacksmith known for crafting the armor of the legendary hero who saved the town" I might get advantage on my check if the DM consider the marchand moved by those reasons or the DM might give me disadvantage, if the marchand hate the king and secretly is part of the group trying to destroy the town. but ultimately, I will roll my persuasion and ask the DM if 25 is enough to get my discount
So it should work the same way with my rogue. I ask tell you my rogue is searching the desk for evidence of corruption. If I add that "I'm looking for secret compartment where they could be hidden" you can give me advantage, but ultimately my perception or investigation check should determine if I find something. even if I do not mention what kind of secret compartment the desk contain or how to open it.

Can I roll Investigation to sweep aside the dust on this thread?

I just want to point out that no skill should ever just be "roll to receive plot." Because you shouldn't call for a roll unless there's a meaningful consequence for failure (DMG 237), and "the plot stops" is not a meaningful consequence - either the game screeches to a halt, or you just deliver the plot by some other means, rendering the roll meaningless.

What Investigation rolls should be used for are:
1) Revealing additional routes to proceed on the critical path - then the meaningful choice for the players becomes choosing the best one, rather than "continue story or don't."
2) Revealing additional information, which will recontextualize character actions or open up new ones down the road. This deepens the plot rather than gating it.
3) Revealing optional / supplementary objectives such as sidequests, extra treasure, or other challenges/rewards. 

Apologies for thread necromancy, but I have a lot to say on this matter.

The example of using perception to rifle through a desk for secret caches or anything of the sort is erroneously using perception. That is most definitely an Investigation check, and I'll explain why:

One of the most straightforward applications of Investigation in the basic rules (and the only real use for the Passive Investigation stat referenced by the Observant feat) is to see through Illusions. With that in mind, what would be different looking at an illusion with Perception vs. Investigation? Well, I imagine if you saw something irl, the tells for it being an illusion would be things your subconscious brain wouldn't immediately pick up on: Things like the light reflecting off it slightly wrong, the shadows not lining up with light sources the same way as nearby objects, wind not effecting it as it does dust and other things nearby, etc. In other words, it's looking at it and using your brain to see things your eyes don't necessarily automatically interpret. 

So back to the desk: A rogue who investigates the desk may look and feel around for seams, but using their brain they may notice a knot in the wood of the desk doesn't flow with the grain of the board that it's in. Upon pushing the knot, they discover that it's in fact a secret button to unlock a hidden compartment. Alternatively, by sitting in the chair behind the desk, they may check what areas would be easily within reach but concealed from the doorway or windows, places that could be discreetly accessed by the mayor without drawing suspicion or notice. They may also see a part of the desk that is a very slightly darker color. On a Perception check, that could easily just mean it's not in the sun or in a spot where wear and tear would discolor it, but an Investigation check may further discover that those places were painted much later in an attempt to match the color, but were slightly off, meaning they indicate alterations that were made to the desk after it was initially produced, pointing to hidden compartments. 

All of those would be Investigation rather than Perception. All of those would be using Intelligence rather than Wisdom. 

Also, as a side note, saying "I'd like to investigate the desk" instead of "I rifle through the drawers and look for clues" isn't rollplaying, and isn't bad either. It's the player using the tools at their disposal to interact with the world the DM has created. Rollplaying would be something like "I'd like to use Persuasion to convince X to join us" rather than actually creating an argument for X to do so. 

The DM could always say, "great your 30 investigation roll has allowed you to determine there's a secret door here... describe how your character figures out how to open it."

If the player is at a complete loss, allow another roll and give them a hint. Just because someone rolls a super high roll, doesn't mean the DM has to hand things to them on a silver plate.

One of my frequent sayings in-game is, "passive perception isn't radar".

In the beginning I struggled to figure out when to ask for Investigation and when to ask for Perception.

I've settled on Perception is looking, smelling, hearing - you walk into a room and see....

Investigation is touching - looking through the stack of papers or inside the desk or through the trash pile....

Perception - You notice a stone which is slightly different from those around it. Players most often say they look at it to figure out what to about it. Many forum games have players making a roll in anticipation to save time, which I don't mind. 

I haven't had a player do a string of rolls to find something out, yet. I honestly don't remember having players try to figure out a puzzle by rolling. Hopefully it's because I present the situation in a way that they know they have to do something not just roll for it. 

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I completely understand that some people are not heavy thinkers or puzzle solvers in real life. Their PC may know the answer that the player does not. That's what rolls are for. 

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