The heart is closely connected to the feelings and affections of a person.

The heart became the focus for all the vital functions of the body; including both intellectual and spiritual life. The heart and the intellect are closely connected,  it is the seat of intelligence;  

For this people's heart is waxed gross, and their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with their eyes, and hear with their ears, and should understand with their heart, and should be converted, and I should heal them.  (Matt. 13:15).

This language wax gross  is commonly applied to "the body," but is also used to denote one who is stupid and foolish in mind. Here it means that the people were so sensual and corrupt that they did not see or understand the pure spiritual principles of the gospel. Lest they should see Lest they should see their lost condition as sinners, and turn and live. The reason given here why they did not hear and understand the gospel is, that their "heart" was "wrong." They "would" not attend to the things that belonged to their peace. I should heal them - Should pardon, sanctify, and save them. Sin is often represented as a disease, and the pardon and recovery of the soul from sin as "healing." The heart is connected with thinking: As a person "thinks in his heart, so is he"  

for as he thinks within himself, so he is. "Eat and drink!" he'll say to you, but his heart won't be with you. (Prov. 23:7).

You are not to judge by his words, but by the constant temper of his mind. To ponder something in one's heart means to consider it carefully as in  (Luke 1:66; and  2:19)

Everyone who heard about it kept thinking what had happened and asked, "What will this child become?" because it was obvious that the hand of the Lord was with him. But Mary treasured up all these things and pondered them in her heart.

She kept them; in her heart she revolved them; she "weighed" them in her mind, giving to each circumstance its just importance, and anxiously seeking what it might indicate respecting her child. "To set one's heart on" is the literal Hebrew that means to give attention to something, to worry about it (1 Sam. 9:20). To call to heart (mind) something means to remember something

Isa 46:8   "Remember this, and stand firm; take it again to heart, you rebels. All of these are functions of the mind, but are connected with the heart in biblical language. Closely related to the mind are acts of the will, acts resulting from a conscious or even a deliberate decision. Each man should give what he has decided in his heart to give, not reluctantly or under compulsion, for God loves a cheerful giver.  2 Corinthians 9:7: "Every man according as he purposed in his heart, so let him give." Ananias contrived his deed of lying to the Holy Spirit in his heart (Acts 5:4). The conscious decision is made in the heart (Rom. 6:17). Connected to the will are human wishes and desires. Romans 1:24 describes how God gave them up "through the lusts of their own hearts, to dishonor their own bodies." David was a man after God's "own heart" because he would "fulfil all" of God's will (Acts 13:22).   Not only is the heart associated with the activities of the mind and the will, but it is also closely connected to the feelings and affections of a person. Emotions such as joy originate in the heart (Ps. 4:7; Isa 65:14).   Finally, the heart is spoken of in Scripture as the centre of the moral and spiritual life. The conscience, for instance, is associated with the heart. In fact, the Hebrew language had no word for conscience, so the word heart was often used to express this concept: "my heart shall not reproach me so long as I live" (Job 27:6). The Revised Standard Version translates the word for "heart" as "conscience" in 1 Samuel 25:31 (RSV). In the New Testament the heart is spoken of also as that which condemns us (1 John 3:19-21). All moral conditions from the highest to the lowest are said to centre in the heart. Sometimes the heart is used to represent a person's true nature or character. Samson told Delilah "all his heart" (Judg. 16:17). This true nature is contrasted with the outward appearance: "man looks on the outward appearance, but the Lord looks on the heart" (1 Sam. 16:7)