Understanding Time Estimation Imagine that “Real Time” is measured by a physical clock, that ticks once a second. We can plot psychological time (on the ordinate) as a function of physical time (on the abscissa). Psychophysics! – A psychophysical function

Some Vocabulary Veridical Perception “Truthful”- corresponding to a known standard. Indexed by a physical measurement, e.g., stop watch, light meter. Accuracy The extent to which an observation matches a standard. Indexed by PSE (mid-point) on psychometric functions. Precision The fineness (“smallness”) of a measurement. Indexed by the slope of psychometric functions. Representation A correspondence between two systems, such that the state of one system provides information about the other system. Can be analogical or symbolic; often used in memory research.

Understanding Time Estimation Physical Time 8 th Notes  On THC Agonist: Physical time seems slow by comparison, as if your psyc clock ticks quickly! Psyc Clock 16 th Notes  (Leftward PSE shift) On Music or THC Antagonist: Physical time seems fast by comparison, as if your psyc clock ticks slowly! Psyc Clock Quarter Notes  (Rightward PSE shift)

Understanding Time Estimation Theories about PSE Shifts in Time Estimation – Internal Clock A biological pace-maker speeds or slows The PSE shift reflects this speeding or slowing – Music or THC antagonist would slow the pace-maker; THC agonist would speed it up. – Memory Bias A sample duration is retrieved from LTM, and compared to accumulated pulses The PSE shift reflects longer versus shorter LTM samples – Music or THC antagonists have us draw longer sample-durations from LTM; we need more ticks to accumulate before the present stimulus matches the LTM sample. We draw briefer LTM samples under THC agonists. – Attention The “pulses” from the biological pace-maker accumulate The failure to select (attend to) a pulse will lead to an under-estimate of the number of accumulated pulses. – We almost always fail to select (fail to attend to) some of the pulses; our attention to the number of pulses is enhanced by TCH agonists, and impaired by music or TCH antagonists.

Time Perception Schematic Decision: If Accumulator > LTM then “Longer”, else “Shorter”. Internal Clock Or Pacemaker (emits pulses) Accumulator (counts pulses) Long Term Memory (LTM)

Time Perception Schematic Decision: If Accumulator > LTM then “Longer”, else “Shorter”. Internal Clock Or Pacemaker (emits pulses) Accumulator (counts pulses) Long Term Memory (LTM)

Internal Clocks & Pharmacology Dopamine Agonists (Methamphetamine)Methamphetamine Reduce PSE (speed the clock)

Internal Clocks & Pharmacology Dopamine Antagonists (Haloperidol)Haloperidol Increase PSE (slow the clock)

Time Perception Schematic Decision: If Accumulator > LTM then “Longer”, else “Shorter”. Internal Clock Or Pacemaker (emits pulses) Accumulator (counts pulses) Long Term Memory (LTM)

Memory Biases & Pharmacology Acyetylcholine Agonists (Physostigmine)Physostigmine Reduce PSE (by shortening “remembered time”)

Memory Biases & Pharmacology Acyetylcholine Antgonists (Atropine)Atropine Increase PSE (by lengthening “remembered time”)

Time Perception Schematic Decision: If Accumulator > LTM then “Longer”, else “Shorter”. Internal Clock Or Pacemaker (emits pulses) Accumulator (counts pulses) Long Term Memory (LTM) Attn

Attention & Time Estimation Theories about Attention & Time Estimation – Attentional Gate Latency There is a delay (latency) in the time at which the participant selects (attends to) pulses. The PSE is increased because the first few internal-clock-pulses do not “register”. – Predicts that the PSE-shift will be the same absolute size regardless of the interval to be timed. – Attentional Flickering The participant’s selection of pulses waxes and wanes, missing some pulses across the entire interval to be timed. The PSE is increased because a fraction of the internal-clock-pulses do not “register”. – Predicts that the PSE-shift will be proportional to the interval to be timed.