Sforno on Genesis 30:38/ספורנו על בראשית ל׳:ל״ח

1לנכח הצאן, he positioned the staves before the line of vision of the sheep in order to make them look when this work was performed, and this experience would be anchored in their imagination at the time they conceived and were pregnant. Visual impressions formed during such periods are of lasting value and usually produce some effect in the young animals born as a result of that pregnancy.