Although the fear response is difficult to assess, Jones and Faure [27] have developed a test known as tonic immobility which has considered the most common measure of fear in poultry [28] and widely used to study fear responses of birds [29]. In our experiment, chicks reared under LED light showed higher tonic immobility than that under ICD light group. Our results illustrated that LED light influenced the fear response of chicks, where LED light would increase the fear responses of chicks. Different results were previously reported in the study of Archer [3]. He demonstrated that raising broilers under LED lights can reduce their fear.