פרשת כי תצא - Lomidsh (critical analysis) Emotions

וְאִם־לֹ֨א קָר֥וֹב אָחִ֛יךָ אֵלֶ֖יךָ וְלֹ֣א יְדַעְתּ֑וֹ וַאֲסַפְתּוֹ֙ אֶל־תּ֣וֹךְ בֵּיתֶ֔ךָ וְהָיָ֣ה עִמְּךָ֗ עַ֣ד דְּרֹ֤שׁ אָחִ֙יךָ֙ אֹת֔וֹ וַהֲשֵׁבֹת֖וֹ לֽוֹ׃

If your fellow Israelite does not live near you or you do not know who [the owner] is, you shall bring it home and it shall remain with you until your peer claims it; then you shall give it back.
עד דרש אחיך. וְכִי תַעֲלֶה עַל דַּעְתְּךָ שֶׁיִּתְּנֵהוּ לוֹ קֹדֶם שֶׁיִּדְרְשֵׁהוּ? אֶלָּא דָּרְשֵׁהוּ שֶׁלֹּא יְהֵא רַמַּאי (בבא מציעא כ"ז; עי' ספרי):
עד דרש אחיך [AND IT SHALL BE WITH THEE] UNTIL THY BROTHER ENQUIRES [FOR IT] — But would it ever enter your mind that one could give it back before he enquires for it (Scripture distinctly states that you do not know to whom the animal belongs)?! But the meaning of the verse is: Thou shalt make diligent enquiries of him that he should not be a fraudulent claimant (Bava Metzia 27b. 28a; cf. Sifrei Devarim 223:4).
אלא אמר רבא סימנין דאורייתא דכתיב (דברים כב, ב) והיה עמך עד דרוש אחיך אותו וכי תעלה על דעתך שיתננו קודם שידרשנו אלא דרשהו אם רמאי הוא או אינו רמאי לאו בסימנין שמע מינה
Rather, Rava said: Identification of an item on the basis of distinguishing marks is by Torah law, as it is written: “And if your brother be not near you, and you know him not, then you shall bring it into your house, and it shall be with you until your brother claims [derosh] it, and you shall return it to him” (Deuteronomy 22:2). Would it enter your mind that he would give the lost item to him before he claims it? How can the finder return it if he does not know the identity of the owner? Rather, the verb derosh is not referring to the claim of the owner; it is referring to the scrutiny performed by the finder. Scrutinize him [darshehu] to determine whether the claimant is a swindler or whether he is not a swindler. Only then may you return the lost item to him. What, is it not that the one who claims the lost item proves that he is not a swindler on the basis of distinguishing marks that he provides? Rava affirms: Conclude from it that identification of an item on the basis of distinguishing marks is by Torah law.
גְּמָ׳ אִתְּמַר מָנֶה לִי בְּיָדְךָ וְהַלָּה אוֹמֵר אֵינִי יוֹדֵעַ רַב יְהוּדָה וְרַב הוּנָא אָמְרִי חַיָּיב וְרַב נַחְמָן וְרַבִּי יוֹחָנָן אָמְרִי פָּטוּר רַב הוּנָא וְרַב יְהוּדָה אָמְרִי חַיָּיב בָּרִי וְשֶׁמָּא בָּרִי עָדִיף רַב נַחְמָן וְרַבִּי יוֹחָנָן אָמְרִי פָּטוּר אוֹקִי מָמוֹנָא בְּחֶזְקַת מָרֵיהּ
GEMARA: It was stated: With regard to one who approaches another and says: I have one hundred dinars in your possession, and the other says: I don’t know, Rav Yehuda and Rav Huna say: The respondent is obligated to pay, because he did not deny the claim, and Rav Naḥman and Rabbi Yoḥanan say: He is exempt from payment. The Gemara elaborates. Rav Huna and Rav Yehuda say that the respondent is obligated to pay based on the principle: When there is a certain claim, e.g., that of the claimant, and an uncertain claim, e.g., that of the respondent, the certain claim prevails. Rav Naḥman and Rabbi Yoḥanan say: The respondent is exempt based on the principle: Establish the money in the possession of its owner, and the burden of proof rests upon the claimant. Since the claimant does not support his claim with proof, the money remains in the possession of the respondent.

Why when someone finds a lost object does he have to ask for proof, he should be considered a 'bori' sure, that is his as he recognises it?

Logic and Emotions are two diffrent parts of the brain...