The everyday infantry droids in the Star Wars prequels and The Clone Wars TV series are dumb as rocks. They are constantly confused, hoodwinked and bamboozled by paper-thin schemes, when they aren't tripping over their own feet into disaster. Yet more advanced droids, like assassin droids, protocol droids and astromechs like C-3PO and R2-D2 are highly intelligent, and referred to as "a dime a dozen" by Obi-Wan (Downfall of a Droid, Clone Wars 1-6). Is there an in-universe explanation of why the Separatists don't equip the infantry droids with better programming?
B1 battle droids are less intelligent because they didn't need to be smart, nor were they designed to be. As a matter of fact, they were originally designed to be coordinated by a Droid Control Ship which would coordinate and direct their strategy, fire patterns and overall tactical movement.
B1 Battle Droid's Role in Combat
The B1's role in combat was to keep blaster fire in the air, absorb damage and buffer incoming fire until more powerful and dangerous droids could be deployed.
After the battle of Naboo, control ships were considered problematic and potentially vulnerable so B1s were forced into semi-autonomy which caused them to behave erratically. Not every B1 Battle Droid was erratic, some through better programming were capable of being leaders, commanders or even commando droids.
To supplement their capacity, Super Battle Droids were created. Super Battle Droids and Droidikas were far more powerful, adaptable, and intelligent. Like any other specialized force, if supported properly, in this case by thousands of B1, such specialist droids could be used to devastating effect against enemy troops.
Was a lack of brainpower a handicap to the B1?
B1 battle droids did not NEED to think, and they weren't INITIALLY designed to think. They had leaders, handlers, or control software to direct their movements in whatever terrain they found themselves in.
B1 battle droids were designed to respond to environmental feedback (other troops, terrain and whatever weapons they had at hand) toward the destruction of their enemies. They didn't need to be particularly bright, their machine programming was more than adequate for most of their missions and could be upgraded over time.
What the B1 battle droid lacked in brainpower, they made up for in numerical superiority. In battle with living enemies, the B1 would be a terrible foe, if for no other reason, their ability to simply absorb damage and continue to press forward.
If B1 and other droids arrived in the proper numbers, it would take a force with a significantly greater power profile to stop their advance. Even adding Jedi to a defending force was often no guarantee of the defenders surviving.
Say what you like about the supposedly idiotic B1 battle droid; in the field, they were able to keep a rain of blaster fire on the enemy, suppressing their movement, tactics and their fire, allowing more potent droids the opportunity to get close, tear into the defenders and simply allow the B1s to pour through any hole created. In terms of strategy, it's simple, but like army ants, the B1 battle droid used it quite effectively.
Because They Are Cheap and Expendable
The most notable aspect of the B1 Battle Droid?
There are lots of them:
B1s were perhaps the most numerous—and expendable—soldiers in galactic history, and, unlike most organic soldiers, they were capable of action in hostile environments such as underwater or in space. They were designed, for the most part, to defeat their enemies through sheer numbers, not through their ability to think (they were very vulnerable to tricks) and utilize combat skills (unlike clone troopers).
To get more of them, they almost were certainly made from cheaper parts. Slower processors, less memory, etc. To put it in modern day terms, they are stupid for the same reason that a Dell $299 special can't run Crysis the way a $4,000 gaming rig can.
In Innocents of Ryloth, Ahsoka comments on this:
"Remember, they are droids. They're just a little slow."
Their less mass produced predecessor, the OOM series, was smarter:
The OOM-series battle droid was the predecessor of the B1 battle droid. While physically identical to the latter, the OOM-series possessed more advanced and independent programming. They were already a common sight in the galaxy before the Invasion of Naboo, serving as security and crew for the Trade Defense Force. They later served in the Clone Wars alongside their more common but simpler B1 descendants.
And during The Clone Wars show, we also see there are more capable commando droids. They are built for stealth, a handful of them could take down a trooper outpost ... but conversely:
The only real drawback of these droids was that they were far more expensive to produce than the regular infantry. This made the droids a fairly rare sight on the battlefield and thus made them to be used exclusively on special and or critical missions only. Apparently, the head was weaker than the rest of its body, as Senator Amidala was able to easily kill one by shooting it in the head with an ELG-3A royal blaster pistol, which was hardly bigger than a hold-out blaster.
So we see a rather consistent trend that the more common the droid, the cheaper they are ... and also the dumber they are. As to why the droids often behave in strange ways, like talking to each other while trying to gun down Jedi's ... this is how all droids in the Star Wars universe work. For whatever reason, droids in Star Wars have personalities - and not just protocol droids. Why does a MSE "mouse" droid "run in fear" from a loud noise?
It may not make logical sense, but however Droid AI works in the Star Wars universe ... this kind of behavior is not uncommon.
As for "constantly confused, hoodwinked and bamboozled by paper-thin schemes" - this usually occurs when the droids aren't doing what they good at ... which is forming a massive army and killing things. As a standing army - they're pretty good. Remember that the Droid Army:
- Would have won the Battle of Naboo had the Central Computer not been destroyed. After this, the reliance on a central command computer was removed
- They present enough of a threat that the Republic has to start mass producing Clones
- Repeatedly in The Clone Wars we are reminded how close the war is ... deals with the Hutts and Rodians in the first season alone are portrayed as vital. As stupid as they are - the droids are remaining a threat against a clone army of Jango Fetts, one of the most capable soldiers in Galactic History.
They're dumb. They are however, effective. When used as designed. And while it is true that they seem to fail at being guards, they are often depicted that way when facing Jedi Knights. A good example of this is "The Hidden Enemy", where:
Anakin, Obi-Wan and their clones prepare to ambush the advancing droid forces from two towers. Just as they are about to fire on the droids, the advances split into three columns and droids suddenly appear in Obi-Wan's building. Anakin calls in a gunship for immediate evacuation before leading his squad to assist Obi-Wan. They escape to the roof, and the droids follow them. Their gunship arrives, picking them up, but not before taking the command tactical droid's head to find out how the Separatists discovered their plan.
In the opening scene we see the B1's used correctly - accompanied by a tactical droid, they very nearly overwhelm and defeat a squad of clones and two Jedi. That is no small threat. They're not built to be smart - they're built to follow orders, walk in columns and keep shooting.
That said, I can't answer why The Separatists don't rely on more human/intelligent assets for roles which require more individualized tasks (which is where the B1 routinely falls short).
They were disposable and used for cannon fodder because it was politically smart to do so; no one cares about droids going off to war, unlike if their sons or fathers were in drafted and killed.
Also too, they are cheap and very effective. Sometimes the enemy doesn't need a smart opponent, but an unyelding, over-powering, overwhelming one, which the droids do in vast numbers. Smart and clever means nothing with a control ship around.
Also too it gave Palpatine the perfect go-to for using the Clones: "but they are smarter and far more effective than mere dumb, droids.."
in a nutshell the Trade Federation are complete cheapskates, the droids have the bare minimum of construction quality, equipment and intelligence. running them through the control ships is another example of this cost saving, while it makes for an obvious military target it's the simplest way to control the army.
as a personal opinion i think it doubtful the Trade Federation really initially used the B-1s with actual warfare in mind instead relying on sheer numbers to intimidate enemies or in the case of Naboo picking what was thought to be an easy target. Also by the time the Clone Wars came around they of course had the super battle droids to handle more serious battles so that by the end of the war the B-1s have been generally relegated to crewing ships instead of combat.
I think this has been stated before by a few people, however I'm going to emphasize it again. Droids in the SW canon behave in a unique way. They seem to carry human traits. They do, however, fall victim to bad programming (especially on the B1s we are referring too).
If we look at arguably the most devastating battle droid conceived, the droideka, we can see that it is used in incredibly small numbers. For instance it is seen twice in ROTS and once in AOTC. Obviously a droid with the ability to contain itself in a shield would be expensive, and so field armies are not made entirely out of them. Expenses would thus play a part in the design of a Droid, which is why the B1 (and to some degree the more beefed up B2) have trouble with decision making.
On the field there is no decisions to make, they are following the orders of a per-established battle plan or the decisions of a command/tactics droid. The only scenes they ever get distracted and confused in is scenes where they have to make decisions because something is out of the ordinary; e.g Jedi accompanying pilots in a Naboo hanger or Obi-wan and Annikan taking a lift full of security droids. Like a raw recruit, they have to first think for themselves whether they need to take action and what action to take. This is where their lack of memory and processing power is there downfall. This also takes us back to the human traits droids carry in Star Wars.
Droids do not follow the same rules our robots and AI follow, what might seem like "competent processing power" in our world is a lack of in the Star Wars Universe. Why do droids bumble and stumble around, why do mouse droids run away from loud noises, why do pit droids (or what ever the fold up, large nosed droids in Phantom Menace's podrace scenes are called) laugh and get annoyed at one another, and why does C3-P0, a protocol droid, talk abuse to his astromech droid friend? These traits set droids and AI in star wars apart and it would seem to answer half your question. Droids, especially B1s, have negative and comical human traits.