PROBLEM TO BE SOLVED: To provide methods of mitigating schizophrenia, schizophreniform disorder, schizoaffective disorder and delusional disorder and improving the cognitive function.SOLUTION: In the method, (R)-7-chloro-N-(quinuclidin-3-yl)benzo[b]thiophene-2-carboxamide, which is an alpha7 nicotinic acetylcholine receptor (alpha7 nAChR) agonist, or a pharmaceutically acceptable salt thereof is administered to a subject at a low daily oral dose of 0.1 to 3 mg.【課題】統合失調症、統合失調症様障害、統合失調感情障害、及び妄想性障害や認知機能を改善する方法の提供。【解決手段】アルファ7ニコチン性アセチルコン受容体(アルファ7nAChR)のアゴニストである、(R)-7-クロロ-N-(キヌクリジン-3-イル)ベンゾ[b]チオフェン-2-カルボキサミド又はその製薬上許容しうる塩を0.1~3mgの低い経口1日投与量で対象に投与されるように用いる医薬。【選択図】なし