Affective piety is most commonly described as a style of highly emotional devotion to the humanity of Jesus, particularly in his infancy and his death, and to the joys and sorrows of the Virgin Mary. It was a major influence on many varieties of devotional literature in late-medieval Europe, both in Latin and in the vernaculars. This practice of prayer, reading, and meditation was often cultivated through visualization and concentration on vivid images of scenes from the Bible, Saints' Lives, Virgin Mary, Christ and religious symbols, feeling from the result. These images could be either conjured up in people's minds when they read or heard poetry and other pieces of religious literature, or they could gaze on manuscript illuminations and other pieces of art as they prayed and meditated on the scenes depicted. In either case, this style of affective meditation asked the "viewer" to engage with the scene as if she or he were physically present and to stir up feelings of love, fear, grief, and/or repentance for sin.

While the texts and art of affective piety could focus on a variety of subjects, they are particularly noted for their gory and violent depictions of the Passion and Crucifixion, as in Richard Rolle's Meditation on the Passion:

Margery Kempe is often used to demonstrate the practice of late-medieval affective piety. In the autobiographical book she dictated to two different scribes, Margery describes her imaginative and emotional reaction during Palm Sunday services:

The Isenheim Altarpiece provides a good, late instance of a piece of art meant to engage the emotions. Images for more intimate, private use can be found in Books of Hours and other manuscripts.

Affective piety can be described as a type of highly emotional devotion, focused on the humanity of Jesus, which developed during the High Middle Ages. Anselm of Canterbury, Bernard of Clairvaux, and Francis of Assisi each played a key role in the development of this approach to spirituality. Traces of an affective sensitivity can be found in Late Antiquity, when clergymen preached sermons with vivid descriptions of the Passion. One example of this is an Eastertide sermon by St. Augustine:

In the chapter on high medieval spirituality in his book The Making of the Middle Ages, the medievalist Richard W. Southern was building on the work of scholars such as André Wilmart and Étienne Gilson. Nevertheless, he is generally credited with having drawn attention to what he (and others) understood to be a shift in devotional practice at the start of the High Middle Ages. He described a "mood of emotional tenderness which runs through the literature of the twelfth century" and considered Anselm of Canterbury to be the quintessential example of an eleventh-century "urge towards a greater measure of solitude, of introspection, and self-knowledge," an urge that "ran like fire through Europe in the generation after his death and produced an outburst of meditations and spiritual soliloquies." Southern, who would go on to write two different biographies of Anselm, argued that "Anselm was the founder of the new type of ardent and effusive self-disclosure," but that "it was the Cistercians who produced the greatest volume, and, as it were, set the fashion in this type of literature."

On Southern's view, both Anselm and the Cistercian abbot Bernard of Clairvaux gave form in their writings to a "theme of tenderness and compassion for the sufferings and helplessness of the Saviour of the world." Anselm, he wrote, "dwelt with passionate intensity on the details of Christ's sufferings," and his prayers "opened up a new world of ardent emotion and piety." Southern attributed this "new feeling about the humanity of the Saviour" to a shift in soteriology, the doctrine concerning how humanity comes to be "saved from the consequences of sin." Southern claimed that the "Devil's Rights", or Ransom Theory, left little room for human action, for according to it salvation was brought about in a "cosmic struggle" in which Satan had to be brought "to break the rules under which he held mankind in fee." Anselm (according to Southern) rejected this theory for one theologians call the Satisfaction Theory of Atonement, in which "Christ suffered as a substitute on behalf of humankind satisfying the demands of God's honor by his infinite merit." This allowed for a "fresh appreciation of the human sufferings of the Redeemer."
Anselm's Orationes sive meditationes (Prayers and Meditations) signalled something that Southern (in his 1990 biography of Anselm) called "The Anselmian Transformation": a shift from the brief, simple, corporate prayers of the Carolingian period to more introspective, private "prolonged ourpourings" spoken in "a language of self-revelation" infused with "theological insight." Anselm, Southern wrote, "added the discipline of exact thought and the warmth of exuberant feeling to the religious impulses of his day." Anselm's prayers work on the emotions; he "strains every resource of language to express and stimulate in his reader both the mental excitation and humiliation necessary for the double activity of self-examination and abasement in the presence of holiness."

In a later generation, Southern argued, Bernard of Clairvaux refined and built on this, and the "imaginative following of the details of the earthly life of Jesus, and especially of the sufferings of the Cross, became part of that programme of progress from carnal to spiritual love which we have called the Cistercian programme." Then, with "St. Francis and his followers, the fruits of the experiences of St. Anselm and St. Bernard were brought to the market place, and became the common property of the lay and clerical world alike." Concerning later affective piety, Southern writes that "the somewhat hectic piety of the fourteenth and fifteenth centuries" resulted from a weakening of the intellectual structure that gave rise to the "surge of pious devotion" of the eleventh and twelfth centuries.