Index: ps/trunk/binaries/data/mods/public/simulation/ai/common-api/gamestate.js
===================================================================
--- ps/trunk/binaries/data/mods/public/simulation/ai/common-api/gamestate.js
+++ ps/trunk/binaries/data/mods/public/simulation/ai/common-api/gamestate.js
@@ -219,7 +219,7 @@
 
 m.GameState.prototype.isResearched = function(template)
 {
-	return this.playerData.researchedTechs[template] !== undefined;
+	return this.playerData.researchedTechs.has(template);
 };
 
 /** true if started or queued */
@@ -242,7 +242,7 @@
 	// researching or already researched: NOO.
 	if (this.playerData.researchQueued[techTemplateName] ||
 	    this.playerData.researchStarted[techTemplateName] ||
-	    this.playerData.researchedTechs[techTemplateName])
+	    this.playerData.researchedTechs.has(techTemplateName))
 		return false;
 
 	if (noRequirementCheck)
@@ -254,7 +254,7 @@
 		let other = template.pairedWith();
 		if (this.playerData.researchQueued[other] ||
 		    this.playerData.researchStarted[other] ||
-		    this.playerData.researchedTechs[other])
+		    this.playerData.researchedTechs.has(other))
 			return false;
 	}
 
@@ -296,7 +296,7 @@
 			switch (type)
 			{
 			case "techs":
-				return req[type].every(tech => !!this.playerData.researchedTechs[tech]);
+				return req[type].every(tech => this.playerData.researchedTechs.has(tech));
 
 			case "entities":
 				return req[type].every(doesEntitySpecPass, this);
Index: ps/trunk/binaries/data/mods/public/simulation/components/TechnologyManager.js
===================================================================
--- ps/trunk/binaries/data/mods/public/simulation/components/TechnologyManager.js
+++ ps/trunk/binaries/data/mods/public/simulation/components/TechnologyManager.js
@@ -20,7 +20,9 @@
 
 TechnologyManager.prototype.Init = function()
 {
-	this.researchedTechs = {}; // technologies which have been researched
+	// Holds names of technologies which have been researched
+	this.researchedTechs = new Set();
+
 	this.researchQueued = {};  // technologies which are queued for research
 	this.researchStarted = {}; // technologies which are being researched currently (non-queued)
 
@@ -94,7 +96,7 @@
 
 TechnologyManager.prototype.IsTechnologyResearched = function(tech)
 {
-	return this.researchedTechs[tech] !== undefined;
+	return this.researchedTechs.has(tech);
 };
 
 TechnologyManager.prototype.IsTechnologyStarted = function(tech)
@@ -274,7 +276,7 @@
 	}
 
 	var modifiedComponents = {};
-	this.researchedTechs[tech] = template;
+	this.researchedTechs.add(tech);
 	// store the modifications in an easy to access structure
 	if (template.modifications)
 	{
@@ -300,8 +302,7 @@
 			if (!i || this.IsTechnologyResearched(i))
 				continue;
 
-			var template = this.GetTechnologyTemplate(i);
-			this.researchedTechs[i] = template;
+			this.researchedTechs.add(i);
 
 			// Change the EntityLimit if any
 			let cmpPlayer = Engine.QueryInterface(this.entity, IID_Player);
@@ -467,10 +468,15 @@
 {
 	return this.researchQueued;
 };
+
+/**
+ * Returns the names of technologies that have already been researched.
+ */
 TechnologyManager.prototype.GetResearchedTechs = function()
 {
 	return this.researchedTechs;
 };
+
 TechnologyManager.prototype.GetClassCounts = function()
 {
 	return this.classCounts;
Index: ps/trunk/binaries/data/mods/public/simulation/components/tests/test_GuiInterface.js
===================================================================
--- ps/trunk/binaries/data/mods/public/simulation/components/tests/test_GuiInterface.js
+++ ps/trunk/binaries/data/mods/public/simulation/components/tests/test_GuiInterface.js
@@ -297,7 +297,7 @@
 			entityLimitChangers: {"Foo": {}},
 			researchQueued: {},
 			researchStarted: {},
-			researchedTechs: {},
+			researchedTechs: new Set(),
 			classCounts: {},
 			typeCountsByClass: {},
 			canBarter: false,
@@ -346,7 +346,7 @@
 			entityLimitChangers: {"Bar": {}},
 			researchQueued: {},
 			researchStarted: {},
-			researchedTechs: {},
+			researchedTechs: new Set(),
 			classCounts: {},
 			typeCountsByClass: {},
 			canBarter: false,
@@ -404,7 +404,7 @@
 			"entityLimitChangers": {"Foo": {}},
 			"researchQueued": {},
 			"researchStarted": {},
-			"researchedTechs": {},
+			"researchedTechs": new Set(),
 			"classCounts": {},
 			"typeCountsByClass": {},
 			"canBarter": false,
@@ -476,7 +476,7 @@
 			"entityLimitChangers": {"Bar": {}},
 			"researchQueued": {},
 			"researchStarted": {},
-			"researchedTechs": {},
+			"researchedTechs": new Set(),
 			"classCounts": {},
 			"typeCountsByClass": {},
 			"canBarter": false,