This distinction primarily stems from BIS Review 8/1997  -3-  the assumption of ‘error-learning’ process in the determination of inflationary expectations workers do have an anticipation on the inflation, but because they judge the inflation performance from the past data, the adjustment between the expected and actual inflation is slow.
“New Economic Challenges and the Fed’s Monetary Policy Review,” speech delivered at “Navigating the Decade Ahead: Implications for Monetary  - 24 Policy,” a symposium sponsored by the Federal Reserve Bank of Kansas City, held in Jackson Hole, Wyo., August 27, https://www.federalreserve.gov/newsevents/speech/powell20200827a.htm. Rachel, Lukasz, and Thomas D. Smith (2017). “Are Low Real Interest Rates Here to Stay?” International Journal of Central Banking, vol.